Morphology of C5 ventral nerve rootlets as part of dissociated motor loss of deltoid muscle

A Meta-Analysis of Surgical Outcomes in 25727 Patients Undergoing Anterior Cervical Discectomy and Fusion or Anterior Cervical Corpectomy and Fusion for Cervical Deformity

STUDY DESIGN

Systematic Review.

OBJECTIVES

To evaluate which cervical deformity correction technique between anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) produces better clinical, radiographic, and operative outcomes.

METHODS

We conducted a meta-analysis comparing studies involving ACDF and ACCF. Adult patients with either original or previously treated cervical spine deformities were included. Two independent reviewers categorized extracted data into clinical, radiographic, and operative outcomes, including complications. Clinical assessments included patient-reported outcomes; radiographic evaluations examined C2-C7 Cobb angle, T1 slope, T1-CL, C2-7 SVA, and graft stability. Surgical measures included surgery duration, blood loss, hospital stay, and complications.

RESULTS

26 studies (25727 patients) met inclusion criteria and were extracted. Of these, 14 studies (19077 patients) with low risk of bias were included in meta-analysis. ACDF and ACCF similarly improve clinical outcomes in terms of JOA and NDI, but ACDF is significantly better at achieving lower VAS neck scores. ACDF is also more advantageous for improving cervical lordosis and minimizing the incidence of graft complications. While there is no significant difference between approaches for most surgical complications, ACDF is favorable for reducing operative time, intraoperative blood loss, and length of hospital stay.

CONCLUSIONS

While both techniques benefit cervical deformity patients, when both techniques are feasible, ACDF may be superior with respect to VAS neck scores, cervical lordosis, graft complications and certain perioperative outcomes. Further studies are recommended to address outcome variability and refine surgical approach selection.

Optimal timing of referral for nerve transfer surgery for postoperative C5 palsy

OBJECTIVE

Cervical nerve 5 palsy can occur following surgery for cervical spine pathology. The prognosis of C5 palsy is generally favorable, and most patients recover useful function. However, some patients do not recover useful strength. Nerve transfers are a potential effective treatment of postoperative severe C5 palsy. This study aimed to further delineate the natural history of recovery from postoperative C5 palsy, determine whether lack of recovery at specific time points predicts poor recovery prognosis, and thereby determine a reasonable time point for referral to a complex peripheral nerve specialist.

METHODS

The authors conducted a retrospective review of 72 patients who underwent surgery for cervical spondylosis and stenosis complicated by C5 palsy. Medical Research Council (MRC) motor strength grades were recorded preoperatively; immediately postoperatively; at discharge; and at 2 weeks, 3 months, 6 months, and 12 months postoperatively. Univariate and multivariate logistic regression models were used to identify demographic and clinical risk factors associated with recovery of useful strength after severe C5 palsy.

RESULTS

The mean patient age was 62.5 years, and 36.1% of patients were female. Thirty patients (41.7%) experienced severe C5 palsy with less than antigravity strength (MRC grade 2 or less) at discharge. Twenty-one (70%) of these patients recovered useful strength (MRC grade 3 or greater) at 12 months postoperatively, and 9 patients (30%) did not recover useful strength at 12 months. Of those patients with persistent severe C5 palsy at 3 months postoperatively, 50% recovered useful strength at 12 months. Of those patients with persistent severe C5 palsy at 6 months postoperatively, 25% recovered useful strength at 12 months. No patient with MRC grade 0 or 1 strength at 6 months postoperatively recovered useful strength. A history of diabetes was associated with the occurrence of severe C5 palsy. On multivariate analysis, female sex was associated with recovery of useful strength.

CONCLUSIONS

Most patients with severe C5 palsy recover useful strength in their C5 myotome within 12 months of onset. However, at 3 months postoperatively, patients with persistent severe C5 palsy had only a 50% chance of recovering useful strength by 12 months. Lack of recovery of useful strength at 3 months postoperatively is a reasonable time point for referral to a complex peripheral nerve center to establish care and to determine candidacy for nerve transfer surgery if severe C5 palsy persists.

Diagnostic Accuracy of Magnetic Resonance Imaging With 3-Dimensional T2-SPACE Techniques for Preganglionic Injury of the Brachial Plexus

PURPOSE

An accurate diagnosis of the site and severity of a brachial plexus injury is imperative for selecting the appropriate management. Conventional magnetic resonance imaging (MRI) does not allow for the precise interpretation of preganglionic injuries (pre-GIs), especially intravertebral canal injuries. We developed 4 MRI sequences of conventional 1.5-tesla 3-dimensional T2-weighted turbo spin echo sampling perfection with the application of optimized contrasts using different flip angles evolution (T2-SPACE) images to clearly visualize each component of the brachial plexus. The purpose of this study was to introduce basic normal and pathologic findings of our current MRI approach, focusing on its diagnostic accuracy for pre-GIs.

METHODS

We initially examined 119 patients with brachial plexus injuries who underwent surgical exploration by MRI using 4 sequences of the 1.5-tesla 3-dimensional T2-SPACE technique. We obtained coronal, transverse, coronal oblique, and coronal cuts of T2 short time inversion recovery. The images of 595 roots were interpreted by multiple-image synchronizing techniques of the 4 views to precisely interpret the presence of spinal cord edema, numbers of anterior and posterior rootlets, sites of ganglions, meningeal cysts, and the "black line sign" (displaced ruptured dura or bundles of ruptured rootlets). We assessed the accuracy, sensitivity, and specificity of these abnormal findings with regard to diagnosing pre-GIs by comparing surgical exploration.

RESULTS

The absence or decreased numbers of anterior and posterior rootlets and displacement of ganglions were definitive evidence of pre-GIs and the other findings, like spinal cord edema, meningeal cysts, and black line signs, were predictive signs.

CONCLUSIONS

The synchronizing techniques of the four 1.5-tesla 3-dimensional T2-SPACE images provided high diagnostic accuracy of pre-GIs.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

A Risk Calculator for the Prediction of C5 Nerve Root Palsy After Instrumented Cervical Fusion

BACKGROUND

C5 palsy is a common postoperative complication after cervical fusion and is associated with increased health care costs and diminished quality of life. Accurate prediction of C5 palsy may allow for appropriate preoperative counseling and risk stratification. We primarily aim to develop an algorithm for the prediction of C5 palsy after instrumented cervical fusion and identify novel features for risk prediction. Additionally, we aim to build a risk calculator to provide the risk of C5 palsy.

METHODS

We identified adult patients who underwent instrumented cervical fusion at a tertiary care medical center between 2013 and 2020. The primary outcome was postoperative C5 palsy. We developed ensemble machine learning, standard machine learning, and logistic regression models predicting the risk of C5 palsy-assessing discrimination and calibration. Additionally, a web-based risk calculator was built with the best-performing model.

RESULTS

A total of 1024 patients were included, with 52 cases of C5 palsy. The ensemble model was well-calibrated and demonstrated excellent discrimination with an area under the receiver-operating characteristic curve of 0.773. The following features were the most important for ensemble model performance: diabetes mellitus, bipolar disorder, C5 or C4 level, surgical approach, preoperative non-motor neurologic symptoms, degenerative disease, number of fused levels, and age.

CONCLUSIONS

We report a risk calculator that generates patient-specific C5 palsy risk after instrumented cervical fusion. Individualized risk prediction for patients may facilitate improved preoperative patient counseling and risk stratification as well as potential intraoperative mitigating measures. This tool may also aid in addressing potentially modifiable risk factors such as diabetes and obesity.

An Experimental Rat Model of C5 Palsy Following Posterior Decompression Surgery of the Cervical Spine

STUDY DESIGN

Basic in vivo research.

OBJECTIVES

The aim of this study was to establish an animal model that is appropriate for analyzing the mechanisms of C5 palsy (C5P) and to clarify the structural and functional alterations of cervical roots following posterior decompression.

SUMMARY OF BACKGROUND DATA

Although C5P is one of the major complications of cervical surgery, the exact pathogenesis of C5P remains unclear partly because of the lack of an appropriate animal model. Tethering of the cervical roots due to posterior cord shift following posterior decompression is thought to be one of the possible factors that cause C5P.

METHODS

Twenty-eight Sprague-Dawley rats were divided into Group L (cervical laminectomy, N = 18) or Group S (sham surgery, N = 10) and examined up to postoperative day 14 (PO14). Posterior cord shift and the length of the anterior rootlets were quantified by computed tomography-myelogram images. Motor evoked potential (MEP) of the deltoid (C5, 6 innervated) and triceps brachii (C7-T1 innervated), mechanical allodynia, and grip strength of the forepaw (C7-T1 regulated) were measured.

RESULTS

All anterior rootlets were elongated as the cord gradually shifted posteriorly postoperatively. The elongation rate of the C6 anterior rootlets was the highest (142% at PO14). The MEP latency of the deltoid was significantly delayed throughout all postoperative time points. However, significant delay in the latency of the triceps brachii was observed only on postoperative day 10. The withdrawal threshold of the forepaw did not change; grip strength of the forelimb decreased at PO14.

CONCLUSION

This model was thought to be appropriate for analyzing the pathogenesis of C5P since our findings were comparable to the clinical course of C5P subsequent to posterior cervical decompression. Although a future study for clarifying histological and molecular alterations will be needed, tethering of the anterior rootlets due to posterior cord shift was suggested to be a probable mechanism causing C5P.Level of Evidence: 5.

Risk Factors and Prevention of C5 Palsy After Anterior Cervical Decompression and Fusion: Similarity of the Pathomechanism With That After a Posterior Approach

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

The objective of this study was to review clinical and imaging findings after anterior cervical decompression and fusion, as a basis for prevention of C5 palsy.

SUMMARY OF BACKGROUND DATA

C5 palsy is a common postoperative complication in spine surgery, but the mechanistic basis for this condition is unknown.

MATERIALS AND METHODS

The subjects were 239 patients with cervical myelopathy who underwent anterior cervical decompression and fusion including at C4-C5 disk level at our hospital from 2001 to 2018. Twelve of these patients (5.0%) had C5 palsy postoperatively. Clinical features and imaging findings were compared in patients with and without C5 palsy.

RESULTS

In patients with C5 palsy, the sagittal alignment of the cervical spine was kyphotic, the width of the C5 intervertebral foramen was narrower, and the lateral decompressed line was wider beyond the medial part of the Luschka joint. Age, sex, disease, the number of fused segments, decompression width, and anterior shift of the spinal cord did not differ significantly between patients with and without C5 palsy.

CONCLUSIONS

These results indicate that the pathomechanism of C5 palsy may be dependent on the location of the lateral decompression line, especially in patients with cervical kyphosis and a narrow C5 intervertebral foramen. Excessive lateral decompression beyond the Luchka joint might lead to C5 root kinking between the intervertebral foramen and posterior edge of vertebra. This pathomechanism may be similar in anterior and posterior approaches. To prevent C5 palsy, the medial line of the Luschka joint should be confirmed intraoperatively and decompression should be performed within the Luschka joints. Alternatively, medial foraminotomy should be used in cases needing wide decompression, such as those with massive ossification of the posterior longitudinal ligament, lateral osteophytes, and symptomatic foraminal stenosis.

LEVEL OF EVIDENCE

Level III.

Impact of morphological restoration of the spinal cord from the preoperative to early postoperative periods on C5 palsy development

OBJECTIVE

C5 palsy (C5P) is a known complication of cervical decompression surgery. The tethering effect of the C5 nerve root following the posterior shift of the spinal cord is the most accepted pathologic mechanism for C5P development; however, this mechanism cannot fully explain C5P by itself in clinical practice. Separately, some studies have suggested that preoperative severe spinal cord compression and postoperative morphological changes in the spinal cord affect C5P development; however, no previous study has quantitatively addressed these possibilities. The aim of this study was to examine whether spinal cord morphology and morphological restoration after surgery affect C5P development.

METHODS

The authors reviewed consecutive patients with degenerative cervical myelopathy who underwent laminoplasty including the C3-4 and C4-5 intervertebral disc levels. All participants underwent MRI both preoperatively and within 4 weeks postoperatively. To assess the severity of spinal cord compression, the compression ratio (CR; spinal cord sagittal diameter/transverse diameter) was calculated. As an index of morphological changes in the spinal cord during the early postoperative period, the change rate of CR (CrCR, %) was calculated as CRwithin 4 weeks postoperatively/CRpreoperatively × 100. These measurements were performed at both the C3-4 and C4-5 intervertebral disc levels. The study cohort was divided into C5P and non-C5P (NC5P) groups; then, CR and CrCR, in addition to other radiographic variables associated with C5P development, were compared between the groups.

RESULTS

A total of 114 patients (mean age 67.6 years, 58.8% men) were included in the study, with 5 and 109 patients in the C5P and NC5P groups, respectively. Preoperative CR at both the C3-4 and C4-5 levels was significantly lower in the C5P group than in the NC5P group (0.35 vs 0.44, p = 0.042 and 0.27 vs 0.39, p = 0.021, respectively). Patients with C5P exhibited significantly higher CrCR at the C3-4 level than those without (139.3% vs 119.0%, p = 0.046), but the same finding was not noted for CrCR at the C4-5 level. There were no significant differences in other variables between the groups.

CONCLUSIONS

This study reveals that severe compression of the spinal cord and its greater morphological restoration during the early postoperative period affect C5P development. These findings could support the involvement of segmental cord disorder theory, characterized as the reperfusion phenomenon, in the pathomechanism of C5P, in addition to the tethering effect.

Analysis of risk factors for C5 nerve root paralysis after posterior cervical decompression

BACKGROUND

C5 nerve root paralysis is a nonnegligible complication after posterior cervical spine surgery (PCSS). The cause of its occurrence remains controversial. The purpose of this study was to analyse the incidence of and risk factors for C5 nerve root paralysis after posterior cervical decompression.

METHODS

We retrospectively analysed the clinical data of 640 patients who underwent PCSS in the Department of Orthopaedics, Affiliated Hospital of Qingdao University from September 2013 to September 2019. According to the status of C5 nerve root paralysis after surgery, all patients were divided into paralysis and normal groups. Univariate and multivariate analyses were used to determine the independent risk factors for C5 nerve root paralysis. A receiver operating characteristic (ROC) curve was used to demonstrate the discrimination of all independent risk factors.

RESULTS

Multivariate logistic regression analysis revealed that male sex, preoperative cervical spine curvature, posterior longitudinal ligament ossification, and preoperative C4/5 spinal cord hyperintensity were independent risk factors for paralysis, whereas the width of the intervertebral foramina was an independent protective factor for paralysis. The area under the curve (AUC) values of the T2 signal change at C4-C5, sex, cervical foramina width, curvature and posterior longitudinal ligament ossification were 0.706, 0.633, 0.617, 0.637, and 0.569, respectively.

CONCLUSIONS

Male patients with C4-C5 intervertebral foramina stenosis, preoperative C4-C5 spinal cord T2 high signal, combined with OPLL, and higher preoperative cervical spine curvature are more likely to develop C5 nerve root paralysis after surgery. Among the above five risk factors, T2 hyperintensity change in C4-C5 exhibits the highest correlation with C5 paralysis and strong diagnostic power. It seems necessary to inform patients who have had cervical spine T2 hyperintensity before surgery of C5 nerve root paralysis after surgery, especially those with altered spinal cord T2 signals in the C4-C5 segment.

Intradural Neuroanatomy in the Cervical Spinal Canal: Importance of a New Anatomic Zone Division and Accurate Assessment of Neural Compression in Myeloradiculopathy Patients

This study defined different anatomic zones within the cervical spinal canal and provides detailed anatomical quantitative data for an accurate diagnosis of cervical spondylosis and a safe and effective anterior decompression surgery.

Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord

OBJECTIVE

To provide precise description of the dorsal and ventral roots orientation along with the main spinal cord anatomical measurements and their segment-specific variations.

PATIENTS AND METHODS

We collected and analyzed the measurements of the spines, spinal cords, and dorsal and ventral roots (C2-L5) of nine adult cadavers (five males and four females).

RESULTS

This study for the first time provides analysis of the dorsal and ventral roots orientation along with spinal cord anatomical measurements and their segment-specific distribution. The results of this study showed less variability in rostral root angles compared with the caudal. Dorsal and ventral rootlets were oriented mostly perpendicular to the spinal cord at the cervical level and had more parallel orientation to the spinal cord at the thoracic and lumbar segments. The number of rootlets per root was greatest at dorsal cervical and lumbar segments. Spinal cord transverse diameter and width of the dorsal columns were largest at cervical segments. The strongest correlation between the spinal cord and vertebrae structures was found between the length of intervertebral foramen to rostral rootlet distance and vertebral bone length.

CONCLUSION

These results demonstrate consistent variation in spinal cord anatomical features across all tested subjects. The results of this study can be used to locate spinal roots and main spinal cord landmarks based on bone marks on computed tomography or X-rays. These results could improve stereotactic surgical procedures and electrode positioning for neuromodulation procedures.

Radiographic Measures of Spinal Alignment Are Not Predictive of the Development of C5 Palsy Following Anterior Cervical Discectomy and Fusion Surgery

BACKGROUND

Postoperative C5 palsy is a common complication following cervical decompression, occurring more frequently after posterior-based procedures. It has been theorized that this is the result of C5 nerve stretch resulting from spinal cord drift with these procedures. As such, it is thought to be less common after anterior cervical decompression and fusion (ACDF). However, no consensus has been reached on its true etiology. The purpose of this study is to assess the rate of C5 palsy following ACDF and to determine whether any radiographic or demographic parameters were predictive of its development.

METHODS

Two hundred and twenty-six patients who received ACDF between September 2015 and September 2016 were reviewed, and 122 were included in the final analysis. Patient demographic, surgical, and radiographic data were analyzed, including preoperative and postoperative radiographic and motor examination results. The Mann-Whitney U test was used to compare continuous variables between independent groups, and Fisher's exact test was used to compare categorical variables between groups.

RESULTS

Seven patients developed a C5 palsy in the postoperative period, an incidence rate of 5.7%. Among the radiographic parameters evaluated, there were no statistically significant differences between the C5 palsy and nonpalsy groups. Additionally, there were no statistically significant differences in age, patient sex, or numbers of vertebral levels fused between groups.

CONCLUSIONS

Ultimately, we did not identify any statistically significant demographic or radiographic predictive factors for the development of C5 palsy following ACDF surgery.

LEVEL OF EVIDENCE

3.

Atypical Proximal Cervical Spondylotic Amyotrophy: Case Report Demonstrating Clinical/Imaging Discrepancy

Purpose

The aim of this study was to present a novel case of unilateral proximal cervical spondylotic amyotrophy (CSA) with contralateral spinal cord compression, which is subject to misdiagnosis and missed diagnosis.

Background

CSA is the rare form of cervical spondylosis, which is characterized by severe muscle atrophy in the upper extremities. It can be classified in the proximal subtype and the distal subtype. The etiology, pathophysiology and treatment of CSA are still controversial.

Methods

A rare case of atypical proximal CSA, who presented with left shoulder and arm weakness, but cervical magnetic resonance imaging (MRI) showed large right paracentral disc herniation in the C4-5 level. Twelve weeks after undergoing anterior cervical discectomy and fusion technique in C4-5 level, the patient’s symptoms obviously recovered.

Conclusion

The opposite sides between disc herniation and clinical symptoms of upper extremity may be attributed to C5 ventral rootlet becoming stretched caused by spinal cord rotation or shift to the opposite side.

Neurological Disturbance of the Upper Extremities After Cervical Laminoplasty: A Morphological Assessment Focused on the Intervertebral Foramen

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to explore the relationship between postoperative neurological disturbance of the upper extremities (NDUE) after cervical laminoplasty and intervertebral foraminal stenosis.

SUMMARY OF BACKGROUND DATA

The relationship between foraminal stenosis and neurological disturbance in the C5 segment (C5 palsy) has been reported, but the relationship at other levels has not been examined before. We evaluated foraminal stenosis morphologically using three-dimensional computed tomography (3D-CT), alongside other risk factors for NDUE.

METHODS

We retrospectively reviewed patients treated by open-door laminoplasty at the authors' institution between January and June 2016. NDUE was defined as postoperative motor deterioration and/or newly emerged sensory disturbance within 2 weeks of surgery. Radiological measurements were performed in bilateral intervertebral foramina from C5 to C8, using 3D-CT. Investigation using magnetic resonance imaging (MRI) was also performed.

RESULTS

Thirty-one patients were reviewed, and 10 (32.3%) developed NDUE. Nineteen NDUE were observed: seven were in the C5 segment, five in the C6 segment, three in the C7 segment, and four in the C8 segment. Four patients (40%) had NDUE from multiple segments. The mean width of the foramen was 2.60 ± 1.26 mm and 3.66 ± 1.66 mm (P = 0.007), and cross-sectional area was 32.8 ± 10.8 mm and 41.6 ± 12.4 mm (P = 0.003), in symptomatic (n = 19) and nonsymptomatic (n = 187) foramina, respectively. The mean transverse diameter of bony spurs and the maximum shift of the spinal cord on MRI was significantly larger in the NDUE group. The odds ratio of having a foraminal cross-sectional area under 28.0 mm in combination with a maximum spinal shift over 3.10 mm was 14.6 (P < 0.001).

CONCLUSION

Stenosis of the intervertebral foramen could be a risk factor for NDUE after cervical laminoplasty, and could be aggravated by excessive posterior spinal cord shift.

LEVEL OF EVIDENCE

3.

Patterns of neurological deficits and recovery of postoperative C5 nerve palsy

OBJECTIVE

Paresis of the C5 nerve is a well-recognized complication of cervical spine surgery. Numerous studies have investigated its incidence and possible causes, but the specific pattern and character of neurological deficits, time course, and relationship to preoperative cord signal changes remain incompletely understood.

METHODS

Records of patients undergoing cervical decompressive surgery for spondylosis, disc herniation, or ossification of the longitudinal ligament, including the C4-5 level, were reviewed from a 15-year period, identifying C5 palsy cases. Data collected included age, sex, diabetes and smoking statuses, body mass index, surgical levels, approach, presence of increased cord signal intensity, and modified Japanese Orthopaedic Association (mJOA) scores. Narrative descriptions of the patterns and findings on neurological examination were reviewed, and complications were noted. The minimum follow-up requirement for the study was 12 months.

RESULTS

Of 642 patients who underwent cervical decompressive surgery, 18 developed C5 palsy (2.8%). The incidence was significantly lower following anterior surgery (6 of 441 [1.4%]) compared with that following cervical laminectomy and fusion (12 of 201 [6.0%]) (p < 0.001). There were 10 men and 8 women whose mean age was 66.7 years (range 54-76 years). The mean preoperative mJOA score of 11.4 improved to 15.6 at the latest follow-up examination. There were no differences between those with and without C5 palsy with regard to sex, age, number of levels treated, or pre- or postoperative mJOA score. Fifteen patients with palsy (83%) had signal changes/myelomalacia on preoperative T2-weighted imaging, compared with 436 of 624 (70%) patients without palsy; however, looking specifically at the C4-5 level, signal change/myelomalacia was present in 12 of 18 (67%) patients with C5 palsy, significantly higher than in the 149 of 624 (24%) patients without palsy (p < 0.00003). Paresis was unilateral in 16 (89%) and bilateral in 2 (11%) patients. All had deltoid weakness, but 15 (83%) exhibited new biceps weakness, 8 (44%) had triceps weakness, and 2 (11%) had hand intrinsic muscle weakness. The mean time until onset of palsy was 4.6 days (range 2-14 days). Two patients (11%) complained of shoulder pain preceding weakness; 3 patients (17%) had sensory loss. Recovery to grade 4/5 deltoid strength occurred in 89% of the patients. No patient had intraoperative loss of somatosensory or motor evoked potentials or abnormal intraoperative C5 electromyography activity.

CONCLUSIONS

Postoperative C5 nerve root dysfunction appears in a delayed fashion, is predominantly a motor deficit, and weakness is frequently appreciated in the biceps and triceps muscles in addition to the deltoid muscle. Preoperative cord signal change/myelomalacia at C4-5 was a significant risk factor. No patient had a detectable deficit in the immediate postoperative period or changes in intraoperative neuromonitoring status. Neurological recovery to at least that of grade 4/5 occurred in nearly 90% of the patients.

The anatomical mechanism of C5 palsy after expansive open-door laminoplasty

BACKGROUND

Postoperative C5 palsy is not an uncommon complication in patients who undergo expansive open-door laminoplasty. However, the etiology is unclear and likely multifactorial. Nerve root lesions and spinal cord lesions have been previously proposed theories.

PURPOSE

To investigate the anatomical mechanism of postoperative C5 palsy after cervical expansive open-door laminoplasty.

STUDY DESIGN

A dissection-based study of eight embalmed human cadavers.

METHODS

The anatomy was studied in eight whole cervical cadavers (three females, five males), prepared with formaldehyde, whose ages at the time of death ranged from 54 to 78 years. Dissection was performed on the intervertebral foramen and spinal canal. In the C3-C7 of the cervical vertebra, the extraforaminal ligaments and the meningovertebral ligaments were observed. The length, width, and thickness of the ligaments were measured with a Vernier caliper. After an expansive open-door laminoplasty was performed, the shape of the dural sac was changed, and displacement of the nerve root was observed. In addition, the lengths of the anterior rootlets were measured. This study has been supported by grants from Science and Technology Planning Project of Guangdong Province (CN) (Grant No. 2017B020210010) without potential conflict of interest-associated biases in the text of the paper.

RESULTS

One hundred seventy-seven extraforaminal ligaments were found to connect the spinal nerve to the surrounding structures. After an expansive open-door laminoplasty was performed, posterior distension of the dural sac and movement of the spinal cord and nerve root were found. The spinal cord was closely attached to the ligamentum flavum by meningovertebral ligaments. In addition, the length of the C5 intradural rootlets (5.81-10.59 mm) was the shortest among the vulnerable segments.

CONCLUSION

Traction on and posterior movement of the extradural roots may be the main pathologic mechanism of postoperative C5 palsy when expansive open-door laminoplasty is performed. The meningovertebral ligaments and extraforaminal ligaments might play an important role in the occurrence of postoperative C5 palsy.

CLINICAL SIGNIFICANCE

This study provides clinicians with a more detailed understanding of the anatomic structure and potential mechanism of C5 palsy. Consideration of the meningovertebral ligaments and the intervertebral foramen may provide new directions for reducing the incidence of this complication.

Morphometric Study of the Cervical Spinal Canal Content and the Vertebral Artery

BACKGROUND

The morphological features of the cervical spinal nerves (C1-C8), their dimensions, and their anatomical relations with the vertebral artery are important for safe spinal surgery. The aim of the present study is to give detailed morphological data of the region to avoid complications.

METHODS

Five formalin-fixed adult cadavers were studied. The cervical spinal nerves and the vertebral artery were exposed via the posterior approach, and detailed anatomy and morphometric measurements were evaluated. The following measurements were documented: angles between the spinal nerve and the spinal cord of C1 to C8, width of the C1 to C8 spinal nerves at their origin, distance of the spinal cord to the vertebral artery, number of dorsal rootlets, length of the dorsal root entry zone of C1 to C8, and distance between respective spinal nerves. Further, the average length and width of the transverse foramen were measured.

RESULTS

The average angle between the spinal cord and the spinal nerve within the vertebral canal ranged between 54 and 87 degrees and were most acute at C5 (54 degrees) compared to the rest of the cervical spinal nerves. The average width of the spinal nerves (mean ± SD), was thickest at C5 (5.7 ± 1.2 mm) and C6 (5.8 ± 0.7 mm). The average largest distance between the vertebral artery and the spinal cord was at C2 (14.3 ± 1.7 mm) and the smallest at C5 (7.3 ± 0.9 mm) and C6 (7.3 ± 2.2 mm) spinal levels. The number of dorsal rootlets was most numerous at C6 (8.25 ± 0.6) and C7 (7.25 ± 0.9). The dorsal root entry zone length was the largest at C5 (13.0 ± 1.6 mm) and C6 (13.75 ± 0.5 mm). The distance between respective spinal nerves was largest between C2 and C3 (11.8 ± 2.2) and C7 and C8 (11.5 ± 0.6).

CONCLUSION

The knowledge of detailed anatomy of the cervical spine (C1-C8) and its relations with the vertebral artery will reduce the unwanted damage to the vital structures of the region.

Foraminal Ligaments Tether Upper Cervical Nerve Roots: A Potential Cause of Postoperative C5 Palsy

Background  Nerve root tethering upon dorsal spinal cord (SC) migration has been proposed as a potential mechanism for postoperative C5 palsy (C5P). To our knowledge, this is the first study to investigate this relationship by anatomically comparing C5–C6 nerve root translation before and after root untethering by cutting the cervical foraminal ligaments (FL).

Objective  The aim of this study is to determine if C5 root untethering through FL cutting results in increased root translation.

Methods  Six cadaveric dissections were performed. Nerve roots were exposed via C4–C6 corpectomies and supraclavicular brachial plexus exposure. Pins were inserted into the C5–C6 roots and adjacent foraminal tubercle. Translation was measured as the distance between pins after the SC was dorsally displaced 5 mm before and after FL cutting. Clinical feasibility of FL release was examined by comparing root translation between standard and extended (complete foraminal decompression) foraminotomies. Translation of root levels before and after FL cutting was compared by two-way repeated measures analysis of variance. Statistical significance was set at 0.05.

Results  Significantly more nerve root translation was observed if the FL was cut versus not-cut, p  = 0.001; no difference was seen between levels, p  = 0.33. Performing an extended cervical foraminotomy was technically feasible allowing complete FL release and root untethering, whereas a standard foraminotomy did not.

Conclusion  FL tether upper cervical nerve roots in their foramina; cutting these ligaments untethers the root and increases translation suggesting they could be harmful in the context of C5P. Further investigation is required examining the value of root untethering in the context of C5P.

Risk factors and preventive measures for C5 palsy after cervical open-door laminoplasty

OBJECTIVE

The pathomechanism of C5 palsy after cervical open-door laminoplasty is unknown despite the relatively common occurrence of this condition postoperatively. The aim of this study was to review clinical and imaging findings in patients with C5 palsy and to propose countermeasures for prevention of this complication.

METHODS

Between 2001 and 2018, 326 patients with cervical myelopathy underwent cervical laminoplasty at the authors' hospital, 10 (3.1%) of whom developed C5 palsy. Clinical features and radiological findings of patients with and without C5 palsy were analyzed.

RESULTS

In patients with C5 palsy, the width of the C5 intervertebral foramen was narrower and the position of the bony gutter was wider beyond the medial part of the C5 facet joint. The distance between the lateral side of the spinal cord and bony gutter was significantly greater in patients with C5 palsy. Patient characteristics, disease, cervical alignment, spinal canal expansion rate, anterior protrusion of the C5 superior articular process, high-intensity area in the spinal cord on T2-weighted MR images, posterior shift of the spinal cord, and operative time did not differ significantly between patients with and without C5 palsy.

CONCLUSIONS

The position of the bony gutter may have a central role in the pathomechanism of postoperative C5 palsy, especially in patients with a narrow C5 intervertebral foramen. Making an excessively lateral bony gutter might be a cause of C5 nerve root kinking at the intervertebral foramen. To prevent the occurrence of C5 palsy, it is important to confirm the medial line of the facet joint on the preoperative CT scan, and a high-speed burr should be started from inside of the facet joint and manipulated in a direction that allows the ligamentum flavum to be identified.

Spinal cord float back is not an independent predictor of postoperative C5 palsy in patients undergoing posterior cervical decompression

BACKGROUND

Of the more than 30,000 posterior cervical spine fusions performed annually, 7%-12% will be complicated by postoperative C5 palsy, a condition characterized by new-onset deltoid weakness with or without C5 dermatomal findings and biceps weakness. Posterior translation of the cervical spinal cord has been proposed as a risk factor for this complication.

PURPOSE

To evaluate if C5 palsy can be predicted by spinal cord float back.

STUDY DESIGN/SETTING

Retrospective cohort.

PATIENT SAMPLE

Patients ≥18 years of age undergoing posterior cervical decompression between 2002 and 2017 for degenerative cervical spine pathologies.

OUTCOME MEASURES

Occurrence of C5 palsy as evaluated by manual motor testing (MMT).

METHODS

We recorded baseline neurological status, operative notes, details of postoperative course, and both pre- and postoperative magnetic resonance imaging images. Float back was defined by the change in the distance between the spinal cord and posterior face of the C4/5 annulus from preoperative to postoperative imaging. C5 palsy was defined by new-onset deltoid weakness on MMT.

RESULTS

We identified 242 patients with a mean age of 62.4 years and mean follow-up of 27.9 months. Forty-two (17.4%) experienced postoperative C5 palsy. On univariable analysis, significant predictors of postoperative C5 palsy were mean C4/5 foraminal diameter (2.8 vs. 3.2 mm; p<.001), anterior projection of the C5 superior articular process (4.12 vs. 3.70 mm; p=.04), cord float back (0.35 vs. 0.28 cm; p=.02), undergoing laminectomy of the C5 (p=.02) or C4 and C5 levels (p=.02), and undergoing instrumented fusion extending one level above and below the C4/5 level. Foraminotomy of the C4/5 level was not predictive of postoperative palsy. On multivariable analysis mean C4/5 foraminal diameter (odds ratio=0.38 per mm; p<.01) predicted C5 palsy; cord float back at the C4/5 level was not predictive of C5 palsy.

CONCLUSIONS

Spinal cord float back was not an independent predictor of C5 palsy on multivariable analysis. Only smaller foraminal diameter was independently predictive of postoperative C5 palsy. This suggests that chronic preoperative compression of the C5 roots, not postdecompression float back may be the biggest contributor to the etiology of postoperative C5 palsy.

Factors Associated With C5 Palsy Following Cervical Spine Surgery: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

C5 palsy (C5P) is a not uncommon and disabling postoperative complication with a reported incidence varying between 0% and 30%. Among others, one explanation for its occurrence includes foraminal nerve root tethering. Although different risk factors have been reported, controversy about its causation and prevention persists. Inconsistent study findings contribute to the persistent ambiguity leading to an assumption of a multifactorial nature of the underlying C5P pathophysiology. Here, we report the results of a systematic review on C5P with narrow inclusion criteria in the hope of elucidating risk factors for C5P due to a common pathophysiological mechanism.

METHODS

Electronic databases from inception to March 9, 2019 and references of articles were searched. Narrow inclusion criteria were applied to identify studies investigating demographic, clinical, surgical, and radiographic factors associated with postoperative C5P.

RESULTS

Sixteen studies were included after initial screening of 122 studies. Eighty-four risk factors were analyzed; 27 in ≥2 studies and 57 in single studies. The pooled prevalence of C5P was 6.0% (range: 4.2%-24.1%) with no consistent evidence that C5P was associated with demographic, clinical, or specific surgical factors. Of the radiographic factors assessed, specifically decreased foraminal diameter and preoperative cord rotation were identified as risk factors for C5P.

CONCLUSION

Although risk factors for C5P have been reported, ambiguity remains due to potentially multifactorial pathophysiology and study heterogeneity. We found foraminal diameter and cord rotation to be associated with postoperative C5P occurrence in our meta-analysis. These findings support the notion that factors contributing to, and acting synergistically with foraminal stenosis increase the risk of postoperative C5P.

Potential Mechanism for Some Postoperative C5 Palsies: An Anatomical Study

STUDY DESIGN

Anatomical Study.

OBJECTIVE

Determine if shoulder depression (eg, taping the shoulders) might result in C5 nerve traction and subsequent injury.

SUMMARY OF BACKGROUND DATA

Postoperative C5 nerve palsy is a recognized entity that is still often enigmatic. Inferior shoulder depression is usually employed to assist with surgical visualization during cervical spine procedures.

METHODS

In the supine position, 10 adult fresh frozen human cadavers underwent dissection of the spinal cord and its adjacent dorsal, ventral roots, and spinal nerves from C4 to T1. In the supine position, the head was rotated ipsilaterally, contralaterally, and in lateral flexion. The shoulder was elevated, retracted, protracted, and depressed all with direct observation of nerve roots, intradural ventral/dorsal rootlets, or the spinal cord. The effects of these movements upon the cervical nerve rootlets were measured.

RESULTS

The greatest displacement of nervous tissue was generated by shoulder depression and occurred primarily at the intradural rootlet level. The nerve rootlets that underwent the greatest average displacement were found at C5, with a decreasing gradient to C7 and no gross motion at C8 or T1. With maximal shoulder depression, C5-C7 rootlet tension produced cord movement to the ipsilateral side, touching the dura mater covering the lateral vertebral column with the C5 nerve root moving farthest.

CONCLUSION

Shoulder depression is often used during cervical spine surgery. In cadavers, shoulder depression causes significant tension and displacement of the C5 nerve rootlets, and in the extreme, cord displacement to the ipsilateral side. This could be a mechanism for injury, putting patients at greater risk for postoperative C5 palsy.

LEVEL OF EVIDENCE

5.

Impact of the surgical strategy on the incidence of C5 nerve root palsy in decompressive cervical surgery

Objective

Our aim was to identify the impact of different surgical strategies on the incidence of C5 palsy.

Background

Degenerative cervical spinal stenosis is a steadily increasing morbidity in the ageing population. Postoperative C5 nerve root palsy is a common complication with severe impact on the patients´ quality of life.

Methods

We identified 1708 consecutive patients who underwent cervical decompression surgery due to degenerative changes. The incidence of C5 palsy and surgical parameters including type and level of surgery were recorded to identify predictors for C5 nerve palsy.

Results

The overall C5 palsy rate was 4.8%, with 18.3% of cases being bilateral. For ACDF alone the palsy rate was low (1.13%), compared to 14.0% of C5 palsy rate after corpectomy. The risk increased with extension of the procedures. Hybrid constructs with corpectomy plus ACDF at C3-6 showed significantly lower rates of C5 palsy (10.7%) than corpectomy of two vertebrae (p = 0.005). Multiple regression analysis identified corpectomy of C4 or C5 as a significant predictor. We observed a lower overall incidence for ventral (4.3%) compared to dorsal (10.9%) approaches (p<0.001). When imaging detected a postoperative shift of the spinal cord at index segment C4/5, palsy rate increased significantly (33.3% vs. 12.5%, p = 0.034).

Conclusions

Extended surgical strategies, such as dorsal laminectomies, multilevel corpectomies and procedures with extensive spinal cord shift were shown to display a high risk of C5 palsy. The use of extended procedures should therefore be employed cautiously. Switching to combined surgical methods like ACDF plus corpectomy can reduce the rate of C5 palsy.

Diagnostic Accuracy of Somatosensory Evoked Potentials in Evaluating New Neurological Deficits After Posterior Cervical Fusions

STUDY DESIGN

This study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict postoperative neurological deficits after posterior cervical fusions (PCF). Eight hundred forty six eligible patients underwent PCF at the University of Pittsburgh Medical Center (UPMC), from 2010 to 2012.

OBJECTIVE

To assess the specificity and sensitivity of intraoperative monitoring in predicting postoperative neurological deficits during PCF.

SUMMARY OF BACKGROUND DATA

We calculated the predictive value, including sensitivity and specificity, of changes in SSEPs to identify neurological deficits postoperatively. We used a receiver operating characteristic (ROC) curve with SSEP categories as cutoff values to further evaluate the diagnostic accuracy of change in SSEPs and postoperative neurological deficit.

METHODS

All patients had preposition baselines and continuous SSEP monitoring throughout the surgery. Statistical analysis was completed using SPSS version 22 (IBM Corp., Armonk, NY).

RESULTS

Age and sex did not influence outcomes. Obesity affected patient outcome. The SSEP categories of significant changes and loss of responses resulted in a sensitivity/specificity of 0.30/0.96 and 0.16/0.98, respectively. The receiver operating characteristic curve has an area under the curve for significant change in/loss of SSEPs of 0.62/0.65 with a 95% confidence interval of 0.525 to 0.714/0.509 to 0.797.

CONCLUSION

Significant SSEP changes during PCF are a very specific but poorly sensitive indicator of postoperative neurological deficits. The odds ratio for significant changes in SSEPs and loss of waveforms was 9.80 and 11.82, respectively, with a 95% confidence interval of 4.695 to 20.46 and 4.45 to 31.41, respectively.

LEVEL OF EVIDENCE

1.

Prognostic Factors for Postsurgical Recovery of Deltoid Palsy due to Cervical Disc Herniations

Study Design

Retrospective multicenter study.

Purpose

We aimed to investigate prognostic factors affecting postsurgical recovery of deltoid palsy due to cervical disc herniation (CDH).

Overview of Literature

Little information is available about prognostic factors affecting postsurgical recovery of deltoid palsy due to CDH.

Methods

Sixty-one patients with CDH causing deltoid palsy (less than grade 3) were included in this study: 35 soft discs and 26 hard discs. Average duration of preoperative deltoid palsy was 11.9 weeks. Thirty-two patients underwent single-level surgery, 22 two-level, four three-level, and three four-level. Patients with accompanying myelopathy, shoulder diseases, or peripheral neuropathy were excluded from the study.

Results

Deltoid palsy (2.4 grades vs. 4.5 grades, p<0.001) and radiculopathy (6.4 points vs. 2.1 points, p<0.001) significantly improved after surgery. Thirty-six of 61 patients (59%) achieved full recovery (grade 5) of deltoid palsy, with an average time of 8.4 weeks. Longer duration of preoperative deltoid palsy and more severe radiculopathy negatively affected the degree of improvement in deltoid palsy. Age, gender, number of surgery level, and disc type did not affect the degree of improvement of deltoid palsy. Contrary to our expectations, severity of preoperative deltoid palsy did not affect the degree of improvement. Due to the shorter duration of preoperative deltoid palsy, in the context of rapid referral, early surgical decompression resulted in significant recovery of more severe grades (grade 0 or 1) of deltoid palsy compared to grade 2 or 3 deltoid palsy.

Conclusions

Early surgical decompression significantly improved deltoid palsy caused by CDH, irrespective of age, gender, number of surgery level, and disc type. However, longer duration of deltoid palsy and more severe intensity of preoperative radiating pain were associated with less improvement of deltoid palsy postoperatively.

Modified K-line in magnetic resonance imaging predicts clinical outcome in patients with nonlordotic alignment after laminoplasty for cervical spondylotic myelopathy

STUDY DESIGN

Retrospective single-center study.

OBJECTIVE

To investigate whether a preoperative index predicts clinical outcome after laminoplasty for cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

This is the first study using the modified K-line, which connects the midpoints of the spinal cord at the C2 and C7 levels on midsagittal magnetic resonance imaging, to assess the relationship between postoperative clinical outcome and anticipated degree of spinal cord shifting.

METHODS

Sixty-one consecutive patients who underwent laminoplasty for the treatment of cervical spondylotic myelopathy between 2000 and 2011 at our hospital were retrospectively reviewed. The interval between the preoperative mK-line and the anterior structure of the spinal canal at each segment of the C3 to C6 levels (INTn, n = 3-6) were measured on sagittal T1-weighted magnetic resonance imaging, and the sum of the INTn (INTsum) was then calculated. The degree of posterior cord shift was defined as follows: %Csum = ΣCn; Cn = (Bn-An) × 100/An (n = 3-6; An and Bn represent the preoperative and postoperative intervals between the midpoint of the spinal cord and the anterior impingement at each segment on sagittal T1-weighted magnetic resonance imaging, respectively). In addition, we defined INTmin as the minimum interval of the INTn in each patient. All patients were divided into lordotic and nonlordotic groups on the basis of lateral neutral radiography. The Japanese Orthopaedic Association (JOA) scoring system and recovery rate of the JOA score for cervical myelopathy was evaluated as clinical outcomes.

RESULTS

The recovery rate of the JOA score was 48.1%. The lordotic and nonlordotic groups contained 38 and 23 patients, respectively. Linear regression analysis revealed that INTmin was significantly correlated with the recovery rate of the patients in the nonlordotic group, whereas INTsum was not associated with recovery of the JOA score.

CONCLUSION

We identified INTmin as a predictive factor for clinical outcomes in patients with nonlordotic alignment after laminoplasty.

LEVEL OF EVIDENCE

4.

Predicting C5 palsy via the use of preoperative anatomic measurements

BACKGROUND CONTEXT

C5 nerve root palsy (C5P) is a relatively rare complication after anterior and posterior cervical decompression surgery that leads to a variety of debilitating symptoms. The precise etiology remains obscure, and a clear understanding of preoperative risk factors for C5P development does not exist.

PURPOSE

To determine whether postoperative C5P can be predicted from preoperative anteroposterior diameter (APD), foraminal diameter (FD), and/or cord-lamina angle (CLA).

STUDY DESIGN

Retrospective review.

PATIENT SAMPLE

Consecutive patients who underwent either anterior or posterior decompression surgery at C4-C5 for cervical spondylotic myelopathy.

OUTCOME MEASURES

Development of C5P.

METHODS

Blinded reviewers retrospectively assessed magnetic resonance images for each included patient's C4-C5 interspace, including the midline APD, the left and right FDs, and the left and right CLA. Multivariable logistic regression was used to model the probability of palsy on the basis of one or more predictors. A jackknife validation was performed to internally validate the model and assess its generalizability.

RESULTS

A total of 98 patients fit the inclusion criteria; 12% had developed symptoms of C5 palsy postoperatively. Using the three variables in a predictor-model, we found that the odds ratio of having palsy for APD, FD, and CLA was 0.3, 0.02, and 1.4, respectively. For every 1-mm increase in APD and FD, the odds of developing palsy decrease 69% (p<.0001) and decrease 98% (p<.0003), respectively. In contrast, for every 1-degree increase in CLA, the odds of developing palsy increase by 43% (p<.0001). The receiver-operating characteristic curve for this three-variable model predicting development of palsy has an area under the curve (concordance index) of 0.97. After implementing a jackknife validation, the area under the curve was 95%.

CONCLUSIONS

This study is the first to use the combination of APD, FD, and CLA to predict development of postoperative C5 palsy after decompression surgery for patients with spondylotic myelopathy. This prediction formula may allow for better patient selection and to prepare patients that have an increased probability of developing this complication.

Morphological distinction of cervical nerve roots associated with motor function in 219 healthy volunteers: a multicenter prospective study

STUDY DESIGN

A prospective study.

OBJECTIVE

To examine the diameter (mm), transverse diameter (mm), and cross-sectional area (mm²) of the C5, C6, and C7 nerve roots using ultrasonography.

SUMMARY OF BACKGROUND DATA

Each of the cervical nerve roots affected a different motor or sensory area. Although there were several studies that performed a detailed assessment of cervical nerve root anatomy in cadavers, only a few studies on the thickness of cervical nerve roots in living specimens have been performed. We examined whether the thickness of the C5, C6, and C7 nerve roots, as well as the area supplied by each of the roots, varied.

METHODS

All 219 subjects (99 males and 120 females; mean age, 47 ± 15 yr) were healthy volunteers. The diameter and the transverse diameter were measured via ultrasonography, and the cross-sectional area was calculated for each of the C5-C7 nerve roots.

RESULTS

The following diameter measurements (right and left, respectively) were obtained: C5, 2.8 and 2.9 mm; C6, 3.6 and 3.8 mm; and C7, 3.3 and 3.4 mm. The following transverse diameter measurements were obtained (right and left, respectively): C5, 2.8 and 3.0 mm; C6, 3.7 and 3.8 mm; and C7, 3.5 and 3.4 mm. The following cross-sectional area measurements (right and left, respectively) were obtained: C5, 6.3 and 6.4 mm²; C6, 10.7 and 11.0 mm²; and C7, 8.8 and 8.8 mm². Based on the 3 measurement methods, the C5 nerve root was significantly thinner than the other 2 nerve roots (P < 0.001), and the C7 nerve root was smaller than the C6 nerve root (P = 0.001).

CONCLUSION

The C5 nerve root was significantly thinner than the C6 and C7 cervical nerve roots. The fact that the C5 nerve is thinner may render it more susceptible to damage during cervical surgery.

Extremely wide and asymmetric anterior decompression causes postoperative C5 palsy: an analysis of 32 patients with postoperative C5 palsy after anterior cervical decompression and fusion

STUDY DESIGN

Single-center retrospective study.

OBJECTIVE

We examined whether extremely wide and asymmetric anterior decompression causes postoperative C5 palsy.

SUMMARY OF BACKGROUND DATA

Postoperative C5 palsy is a complication of cervical decompression surgery. We hypothesized that C5 palsy may be caused by nerve root impairment through extremely wide and asymmetric dural expansion due to unilateral predominant wide anterior decompression with concomitant C4-C5 foraminal stenosis.

METHODS

The study included 32 patients with postoperative C5 palsy from a cohort of 459 patients who underwent anterior cervical decompression and fusion at the C4-C5 disc level for cervical myelopathy. The 64 upper extremities were divided into 2 groups according to palsy side (n = 35) or nonpalsy side (n = 29). Also, to correlate radiological findings, 66 consecutive patients who underwent anterior cervical decompression and fusion without postoperative C5 palsy were selected as control.

RESULTS

In patients with C5 palsy, the unilateral decompression width on the palsy side was significantly larger than that on the nonpalsy side (8.63 vs. 6.92 mm, P = 0.0003). In addition, the decompression width was significantly larger (15.69 vs. 14.38 mm, P = 0.02), the diameter of the C4-C5 foramen was significantly smaller (2.73 vs. 3.24 mm, P = 0.0008), the anterior spinal cord shift was significantly smaller (0.14 vs. 0.73 mm, P< 0.0001), and significant decompression asymmetry (0.74 vs. 0.89, P = 0.0003) was present in the patients with C5 palsy compared with controls.

CONCLUSION

Extremely wide and asymmetric decompression concomitant with pre-existing C4-C5 foraminal stenosis may cause postoperative C5 palsy. Our findings should be valuable for surgeons considering anterior cervical decompression and fusion that includes the C4-C5 level. Surgeons should consider restriction of the decompression width to less than 15 mm and avoiding asymmetric decompression to reduce the incidence of C5 palsy.

Neurological complications of cervical spine surgery: C5 palsy and intraoperative monitoring

STUDY DESIGN

Review article.

OBJECTIVE

To review the epidemiology, etiology, risk factors, prevention, and treatment of neurological complications associated with cervical spine surgery. The article focuses on C5 palsy and intraoperative neurophysiological monitoring.

SUMMARY OF BACKGROUND DATA

Neurological problems are the complications most feared by patients and surgeons alike, but, fortunately, spinal cord injury is uncommon. C5 palsy is a less severe but much more common and perplexing problem. Intraoperative monitoring is widely used in cervical spine surgery, but it is unclear how effective it is at preventing spinal cord or nerve root injury.

METHODS

Narrative and review of the literature.

RESULTS

The incidence of new, severe motor weakness in 2 or more extremities occurring within 12 hours of surgery is 0.18%. The rate in the cervical spine is 3 of 1000. The incidence of isolated C5 palsy is much greater; the rate varies between 0% and 30%, depending on how the condition is defined and which patient group is being analyzed. Numerous theories have been postulated to explain the pathogenesis of C5 palsy, and preventative strategies are discussed. Approximately 70% of patients recover completely without treatment. The mean time to full recovery is 4 to 5 months. Recovery is spontaneous; no treatment has been shown to shorten the time to recovery or improve the recovery rate. A systematic review of the literature found a high level of evidence that multimodal intraoperative monitoring is effective at detecting intraoperative neurological injury. The evidence that intraoperative monitoring reduces the rate of new or worsened perioperative neurological deficits is not as strong. Algorithms help surgeons respond to monitoring alerts and manage neurological deficits that are identified postoperatively.

CONCLUSION

The keys to managing neurological complications in cervical spine surgery are prevention through careful planning, appropriate multimodal monitoring, meticulous surgical technique, and decisive action when a problem is identified.

Middle-term results of a prospective comparative study of anterior decompression with fusion and posterior decompression with laminoplasty for the treatment of cervical spondylotic myelopathy

STUDY DESIGN

A clinical prospective study.

OBJECTIVE

To assess whether clinical and radiologic outcomes differ between anterior decompression and fusion (ADF) and laminoplasty (LAMP) in the treatment of cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

No reports to date have accurately and prospectively compared middle-term clinical outcomes after anterior and posterior decompression for CSM.

METHODS

We prospectively performed LAMP (n = 50) in 1996, 1998, 2000, and 2002, and ADF (n = 45) in 1997, 1999, 2001, and 2003. The Japanese Orthopedic Association (JOA) score, recovery rate, and each item of the JOA score were evaluated. For radiographic evaluation, the lordotic angle and range of motion (ROM) at C2-C7 and residual anterior compression to the spinal cord (ACS) after LAMP on magnetic resonance imaging were investigated.

RESULTS

Eighty-six patients (ADF n = 39; LAMP n = 47) could be followed for more than 5 years (follow-up rate 91.5%). Demographics were similar between the two groups. The mean JOA score and recovery rate in the ADF group were superior to those in the LAMP group from 2-year data collected after surgery. However, LAMP was safer and less invasive than ADF with respect to physical status and complications in the perioperative period. For individual items of the JOA score, the ADF group showed significantly more improvement of upper extremity motor function than the LAMP group (P < 0.05). There was a significant difference in maintenance of the lordotic angle in the ADF group compared with the LAMP group despite no difference in ROM.The LAMP group was divided into two subgroups: (1) LAMP(+) (n = 16) comprising patients who had ACS at 2 years after surgery, and (2) LAMP(-) (n = 31) comprising patients without ACS. Recovery rate differed significantly between the LAMP(+) and LAMP(-) groups despite there being no difference between the LAMP(-) and ADF groups.

CONCLUSION

The recovery rate of the JOA score in the ADF group was better than that in the LAMP group. The clinical outcomes after LAMP could be influenced by ACS.

Neurologic improvement after thoracic, thoracolumbar, and lumbar spinal cord (conus medullaris) injuries

STUDY DESIGN

Retrospective.

OBJECTIVE

With approximately 10,000 new spinal cord injury (SCI) patients in the United States each year, predicting public health outcomes is an important public health concern. Combining all regions of the spine in SCI trials may be misleading if the lumbar and sacral regions (conus) have a neurologic improvement at different rates than the thoracic or thoracolumbar spinal cord.

SUMMARY OF BACKGROUND DATA

Over a 10-year period between January 1995 to 2005, 1746 consecutive spinal injured patients were seen, evaluated, and treated through a level 1 trauma referral center. A retrospective analysis was performed on 150 patients meeting the criteria of T4 to S5 injury, excluding gunshot wounds. One-year follow-up data were available on 95 of these patients.

METHODS

Contingency table analyses (chi-squared statistics) and multivariate logistic regression. Variables of interest included level of injury, initial American Spinal Injury Association (ASIA), age, race, and etiology.

RESULTS

A total of 92.9% of lumbar (conus) patients neurologically improved one ASIA level or more compared with 22.4% of thoracic or thoracolumbar spinal cord-injured patients. Only 7.7% of ASIA A patients showed neurologic improvement, compared with 95.2% of ASIA D patients; ASIA B patients demonstrated a 66.7% improvement rate, whereas ASIA C had a 84.6% improvement rate. When the two effects were considered jointly in a multivariate analysis, ASIA A and thoracic/thoracolumbar patients had only a 4.1% rate of improvement, compared with 96% for lumbar (conus) and incomplete patients (ASIA B-D) and 66.7% to 72.2% for the rest of the patients. All of these relationships were significant to P < 0.001 (chi-square test). There was no link to age or gender, and race and etiology were secondary to region and severity of injury.

CONCLUSION

Thoracic (T4-T9) SCIs have the least potential for neurologic improvement. Thoracolumbar (T10-T12) and lumbar (conus) spinal cord have a greater neurologic improvement rate, which might be related to a greater proportion of lower motor neurons. Thus, defining the exact region of injury and potential for neurologic improvement should be considered in future clinical trial design. Combining all anatomic regions of the spine in SCI trials may be misleading if different regions have neurologic improvement at different rates. Over a ten-year period, 95 complete thoracic/thoracolumbar SCI patients had only a 4.1% rate of neurologic improvement, compared with 96.0% for incomplete lumbar (conus) patients and 66.7% to 72.2% for all others.

Detection of postoperative neurologic deficits using somatosensory-evoked potentials alone during posterior cervical laminoplasty

BACKGROUND CONTEXT

The use of neurophysiologic monitoring during anterior and posterior cervical decompression procedures in patients with spondylotic myelopathy remains controversial. The ideal neurophysiologic monitoring modality of choice is also highly debated.

PURPOSE

The purpose of this study was to evaluate the utility of neurophysiologic monitoring with only somatosensory-evoked potentials (SSEPs) in a consecutive series of laminoplasty procedures with regard to the detection of new postoperative neurologic deficits.

STUDY DESIGN

Retrospective case series.

PATIENT SAMPLE

Eighty consecutive patients who underwent a posterior cervical laminoplasty were reviewed.

OUTCOME MEASURES

We analyzed intraoperative SSEP amplitude and latency changes from baseline with regard to the development of new postoperative neurologic deficits.

METHODS

We retrospectively reviewed 80 patients who underwent a posterior cervical "open-door" laminoplasty with a standard SSEP neurophysiologic monitoring protocol. Intraoperative SSEP amplitude and latency changes from baseline ("alerts") were analyzed with regard to the development of new postoperative neurologic deficits.

RESULTS

Baseline SSEP values were obtained in all patients. There were five (6%) procedures that had SSEP alerts. All alerts occurred shortly after the lamina was hinged open. Four patients with SSEP alerts developed new postoperative neurologic deficits, including three unilateral upper extremity motor and sensory deficits and one complete spinal cord injury. In the immediate postoperative period, our experience with SSEP monitoring demonstrated 4 true-positive, 75 true-negative, and 1 false-positive monitoring results.

CONCLUSIONS

In this series of laminoplasty procedures, SSEP neurophysiologic monitoring had a high sensitivity and specificity for predicting new neurologic deficits in the early postoperative period. Somatosensory-evoked potentials are an effective tool for spinal cord monitoring when performing a posterior cervical laminoplasty procedure.

Longitud de las raíces cervicales en resonancia magnética: relación con la parálisis postoperatoria de la quinta raíz cervical

OBJETIVO: determinar la longitud de la raíz C5. MÉTODOS: se estudiaron con resonancia magnética (Signa 1,5 T, cortes axiales de 5 mm de espesura, TR=850, TE=26, FOV=200) las columnas cervicales de 50 pacientes (29 hombres - 21 mujeres) entre 26 y 68 años. Se incluyeron solo casos con cervicalgia y/o cervicobraquialgia. Se midió (en mm) la longitud de las raíces cervicales tercera a séptima, derechas e izquierdas. La comparación de los promedios se realizó a través del análisis de varianza, para un nivel de significación α=0,05 con IC de 95%. Las comparaciones post-hoc se hicieron empleando el test de Bonferroni. RESULTADOS: se observó que el lado (derecho o izquierdo) y el sexo (varón o mujer) no tuvieron incidencia estadísticamente significativa en el valor de la longitud de las raíces (p>0,05). La raíz C5 tuvo un tamaño significativamente diferente (p<0,05) a cada una de las raíces, pero se comprobó que la raíz más corta era C3. CONCLUSIÓN: la raíz C5 no es la más corta.

Microsurgical posterior foraminotomy with laminoplasty for cervical spondylotic radiculomyelopathy including cervical spondylotic amyotrophy

Object

The authors retrospectively investigated the surgical outcomes and radiographically documented changes after microsurgical posterior foraminotomy with en bloc laminoplasty in patients with cervical spondylotic radiculo-myelopathy (CSRM), including cervical spondylotic amyotrophy (CSA), during a period greater than 2 years.

Methods

Thirty-four consecutive patients (24 men and 10 women) were included in this study. Twenty patients had preoperative radicular pain, and CSA was diagnosed in 14 patients. The mean age at the time of surgery was 61 years (range 43–77 years). The follow-up period ranged from 2 to 6.5 years (mean 3.4 years). Foraminotomy was performed at 49 sites. Neurological improvement was evaluated using the Japanese Orthopaedic Association (JOA) scoring system; radicular pain and deltoid muscle strength were also evaluated clinically. Cervical lordosis, flexion–extension angles, range of motion (ROM), and the angulation and the extent of vertebral slippage at the affected nerve root levels were measured preoperatively and at last follow-up examination.

The mean rate of JOA score improvement was 67.2% (range 22.2–100%). In all 20 patients, preoperative radicular pain completely resolved after surgery. In all 14 patients with CSA, deltoid muscle strength improved; in approximately 80% of these patients, there was either no muscle weakness or only slight weakness. The flexion angles and ROM significantly decreased at the time of the last follow-up examination (p = 0.0402 and 0.0196, respectively). No other items changed significantly.

Conclusions

The aforementioned surgical procedure was safely completed and the surgical outcomes were satisfactory for CSRM including CSA. The instability (the angulation and the vertebral slippage) did not significantly change after surgery. This procedure yielded outstanding results and should be considered an option for cervical laminoplasty in the future.

Investigation of Motor Dominant C5 Paralysis After Laminoplasty From the Results of Evoked Spinal Cord Responses

BACKGROUND

Postoperative motor dominant C5 paralysis was known as one of several complications after laminoplasty. Several theories have been proposed for postoperative segmental paralysis after laminoplasty, but its etiology remains unclear.

OBJECTIVE

To investigate the possible mechanism for postoperative motor dominant C5 paralysis from intraoperative electrophysiological studies using evoked spinal cord potentials (ESCPs).

METHODS

A total of 66 patients who had undergone laminoplasty due to compressive cervical myelopathy were studied retrospectively. In all patients, the symptomatic intervertebral levels of cervical myelopathy were identified by several types of the ESCPs. Motor dominant C5 paralysis was determined as at least 1 level down compared with pre-operative shoulder abduction according to the manual muscle testing.

RESULTS

Five patients (7.6%) showed postoperative motor dominant C5 paralysis. C5 paralysis occurred from 1 to 3 days after surgery and compromised unilaterally in all 5 patients. The causes of cervical myelopathy were cervical spondylosis in 3 patients and ossification of the posterior longitudinal ligament in 2 patients. One patient with severe impairment (2 in manual muscle-testing [MMT] scale) did not show clinical recovery. The other 4 patients recovered to 4 or 5 on the MMT score from 3 to 6 months after the onset. Based on the findings of ESCPs, the C4-5 level was affected by cervical myelopathy in all 5 patients with postoperative motor dominant C5 paralysis (C4-5 level in 3 patients, both C4-5 and C5-6 levels in 2 patients). A high signal intensity area on T2-weighted magnetic resonance imaging (MRI) was observed in all patients who showed apparent motor dominant C5 paralysis in this study.

CONCLUSIONS

Cervical myelopathy at the C4-5 level is a potential risk for motor dominant C5 paralysis. Although it is merely a speculation, when C5 radiculopathy occurs after laminoplasty, C5 paralysis becomes clinically apparent because the deltoid muscle gets predominantly innervated by C5 root due to intramedullary spinal cord damage on the C6 segment in C4-5 myelopathy before surgery. It may represent the high signal intensity area on T2-weighted MRI at the C4-5 level.

Neuroanatomy of the brachial plexus: The missing link in the continuity between the central and peripheral nervous systems

The brachial plexus is a complex network of nerves which extends from the neck to the axilla and which supplies motor, sensory, and sympathetic fibers to the upper extremity. Generally it is formed by the union of the ventral primary rami of the spinal nerves, C5-C8 and T1, the so-called "roots" of the brachial plexus. The goal here is to examine the neural architecture of the brachial plexus. The most constant arrangement of nerve fibers will be delineated, and then the predominant variations in neural architecture will be defined, particularly the prefixed and postfixed plexus, as well as the microanatomy and anatomy of the major terminal branches of the plexus. Multiple tracts connect many parts of the nervous system, and multiple ascending and descending tracts connect the peripheral nervous system (PNS) and lower spinal centers with the brain. This reflects that the nervous system is able to extract different pieces of sensory information from its surroundings and encode them separately, and that it is able to control specific aspects of motor behavior using different sets of neurons. Examination of the major sensory or motor pathways reveals a highly and tightly organized nervous system. In particular, at each of many levels, we see fairly exact maps of the world within the brain. In an effort to understand the functional neuroanatomy of the brachial plexus, this paper will focus briefly on the nervous connections of the nerves of the upper extremity with the brain. The goal here is to better understand "what the brain sees" after nerve injury and repair.

Radiculopathy of C-5 after anterior decompression for cervical myelopathy

Object. The authors conducted a study to examine the incidence and causes of postoperative C-5 radiculopathy, and they suggest preventive methods for C-5 palsy after anterior corpectomy and fusion.

Methods. The authors included in the study 18 patients with postoperative C-5 radiculopathy from 563 patients who underwent anterior decompression and fusion for cervical myelopathy.

There were 10 cases of ossification of the posterior longitudinal ligament (OPLL) and eight cases of cervical spondylotic myelopathy (CSM). All patients received conservative treatment. Posttreatment full recovery was present in eight patients, and Grade 3/5 strength was documented in six in whom some weakness remained.

Radiographic evaluation revealed that the C3–4 and C4–5 cord compression was significantly more severe in patients with paralysis than in those without paralysis. The incidence of paralysis was higher in patients with OPLL than in those with CSM (chi-square test, p = 0.03). The incidence of paralysis increased in parallel with the number of fusion levels (correlation coefficient r = 0.94). Multivariate analysis revealed that the final manual muscle testing (MMT) value was closely related to the preoperative MMT value (computed t value 4.17; p < 0.01) and preoperative Japanese Orthopaedic Association (JOA) score for cervical myelopathty (computed t value, 2.75; p < 0.05).

Conclusions. Preexisting severe stenosis at C3–4 or C4–5 in patients with OPLL is a risk factor for paralysis. Preoperative muscle weakness and a low JOA score are factors predictive of poor recovery.

Comparison of clinical and radiographic outcome in instrumented anterior cervical discectomy and fusion with or without direct uncovertebral joint decompression

BACKGROUND CONTEXT

Anterior cervical discectomy and fusion (ACDF) is an established procedure for the operative treatment of cervical disc disease in patients with radiculopathy resulting from impingement from uncovertebral joint osteophytes. Studies demonstrate that direct decompression of the lesion provides good result. However, known complications include vertebral artery injury, dural tears, nerve root injury, loss of biomechanical stability and increased operative time. Other studies suggest that disc space distraction may play an important role by indirectly decompressing neural elements. Therefore, if equivalent functional outcomes can be achieved without sacrificing the uncovertebral joint, then potential morbidity and mortality could be decreased.

PURPOSE

To assess and compare clinical and radiographic outcomes of patients with neck pain and cervical radiculopathy who underwent instrumented ACDF with or without direct uncovertebral joint decompression.

STUDY DESIGN/SETTING

Retrospective clinical chart and radiographic review to assess clinical outcome and graft fusion in 109 patients who underwent one- or two-level ACDF with rigid anterior plate fixation.

PATIENT SAMPLE

Radiographs and clinical charts for 109 patients (mean, 46 years; range, 27 to 83) who underwent ACDF with rigid anterior plate fixation were retrospectively reviewed at a single institution. Patients with radiculopathy resulting from herniated disc, spondylosis or a combination of both refractory to conservative treatment underwent surgery using a standard Smith-Robinson left-sided approach. Seventy-one patients who received direct uncovertebral joint decompression (Group 1) were compared with 38 patients without direct decompression but indirect decompression by disc space distraction (Group 2). In Group 1, 37 one-level and 34 two-level ACDFs were performed. In Group 2, 11 and 27 were one-level and two-level ACDFs, respectively. Smoking and work-related injuries involved 26.7% and 38.0% of Group 1 and 28.9% and 28.9% of Group 2, respectively. Autologous iliac crest grafts were used in 51 patients, whereas 58 patients received allograft.

OUTCOME MEASURES

Independent blinded analyses of plain lateral neutral, flexion and extension radiographs were conducted to assess fusion, evaluate graft and plate and screw integrity (mean, 12 months). Clinical outcomes were reported as excellent, good, fair or poor (mean, 23 months) based on Odom's criteria.

METHODS

Postoperative clinical outcome and radiographic studies of graft and instrument integrity were assessed in 71 patients undergoing ACDF with uncovertebral joint decompression and 38 patients without uncovertebral joint decompression, but with indirect decompression through disc space distraction.

RESULTS

Fusion occurred in 95.8% of Group 1 and 100% of Group 2. In Group 1, 26.8% of the patients reported excellent results, 57.7% reported good results, 12.7% reported fair results and 2.8% reported poor results. In Group 2, 23.7% of the patients reported excellent results, 60.5% reported good results and 15.8% reported fair results. All nonunions reported good outcomes. Postoperative respiratory distress developed in one patient and dysphagia developed in another both from Group 1. No other complications were noted. The presence or absence of direct uncovertebral joint decompression and clinical outcome was not statistically significant (p>.05). The use of graft-type, operative level, presence of smoking and work-related injury in relation to clinical outcome was not found to be significant (p>.05).

CONCLUSION

Good to excellent results were obtained in 84.5% and 84.2% of patients for Groups 1 and 2, respectively. Indirect foraminal decompression through distraction remains somewhat controversial during ACDF. However, sacrificing the uncovertebral joint can increase operative time and potentially increase complication rates. This study demonstrates that ACDF with or without direct uncovertebral joint decompression can provide good clinical results for neck pain with cervical radiculopathy. Therefore, routine direct uncovertebral joint decompression should not be undertaken during ACDF.

Surgical management of dissociated motor loss following complex cervical spine reconstruction

STUDY DESIGN

A case of surgical management of dissociated motor loss after decompression of the cervical spine is reported.

OBJECTIVES

To present a rationale for surgical treatment of postdecompressive cervical radiculopathy with an illustrative case example.

SUMMARY OF BACKGROUND DATA

The unusual complication of radiculopathy after multilevel cervical decompressive procedures is characterized by pain or dissociated motor weakness of the C5 and C6 nerve roots. Conservative management paradigms, including analgesics and steroids, are the rule, but symptoms often persist for many months. There are currently no reports describing foraminotomy as a means of more rapidly alleviating the symptoms of radicular pain and deltoid and biceps brachii weakness seen in the postoperative setting.

METHODS

We present a case of bilateral C5 and C6 radiculopathy following multilevel cervical decompression for cervical spondylotic myelopathy, which we treated with posterior foraminotomies.

RESULTS

The patient reported complete resolution of his dermatomal pain and demonstrated rapid improvement in upper extremity strength as compared to traditional conservative treatments. The historical experience and pathogenesis regarding this postoperative complication are reviewed. The rationale of root-specific posterior decompression for this debilitating complication is discussed.

CONCLUSIONS

Foraminal decompression of the affected nerve roots as demonstrated here has not been described for postdecompressive dissociated motor loss. Such an approach may offer earlier and more complete relief to patients suffering from this unfortunate complication.

Clinical analysis of cervical radiculopathy causing deltoid paralysis

In general, deltoid paralysis develops in patients with cervical disc herniation (CDH) or cervical spondylotic radiculopathy (CSR) at the level of C4/5, resulting in compression of the C5 nerve root. Therefore, little attention has been paid to CDH or CSR at other levels as the possible cause of deltoid paralysis. In addition, the surgical outcomes for deltoid paralysis have not been fully described. Fourteen patients with single-level CDH or CSR, who had undergone anterior cervical decompression and fusion for deltoid paralysis, were included in this study. The severity of deltoid paralysis was classified into five grades according to manual motor power test, and the severity of radiculopathy was recorded on a visual analog scale (zero to ten points). The degree of improvement in both the severity of deltoid paralysis and radiculopathy following surgery was evaluated. Of 14 patients, one had C3/4 CDH, four had C4/5 CDH, three had C4/5 CSR, one had C5/6 CDH, and five had C5/6 CSR. Both deltoid paralysis and radiculopathy improved significantly with surgery (2.57+/-0.51 grades vs 4.14+/-0.66, P=0.001, and 7.64+/-1.65 points vs 3.21+/-0.58, P=0.001, respectively). In conclusion, the current study demonstrates that deltoid paralysis can develop due to CDH or CSR not only C4/5, but also at the levels of C3/4 and C5/6, and that surgical decompression significantly improves the degree of deltoid paralysis due to cervical radiculopathy.

Differential Diagnosis and Management of Spinal Nerve Root-related Pain

Pain originating from spinal nerve roots demonstrates multiple pathogeneses. Distinctions in the patho-anatomy, biomechanics, and pathophysiology of spinal nerve roots contribute to pathology, diagnosis, and management of root-related pain. Root-related pain can emerge from the tension events in the dura mater and nerve tissue associated with primary disc related disorders. Conversely, secondary disc-related degeneration can produce compression on the nerve roots. This compression can result in chemical and mechanical consequences imposed on the nervous tissue within the spinal canal, lateral recess, intervertebral foramina, and extraforminal regions. Differences in root-related pathology can be observed between lumbar, thoracic, and cervical spinal levels, meriting the implementation of different diagnostic tools and management strategies.

Bilateral phrenic nerve palsy as a complication of anterior decompression and fusion for cervical ossification of the posterior longitudinal ligament

STUDY DESIGN

A case report of bilateral phrenic nerve palsy as a complication of anterior decompression and fusion for cervical ossification of the posterior longitudinal ligament (OPLL).

OBJECTIVES

To present a case of a rare and serious complication of cervical spinal surgery and to investigate its cause.

SUMMARY OF BACKGROUND DATA

There have been a number of reports of phrenic nerve palsy after cardiac surgery, but the authors have found no previous description of this complication related to spinal surgery.

METHODS

The authors describe the clinical presentation and management of a case of bilateral phrenic nerve palsy subsequent to the surgery for cervical OPLL. Also, the literature is reviewed concerning surgical approaches for the treatment of OPLL and the occurrence of phrenic nerve palsy subsequent to any form of therapy.

RESULTS

Bilateral phrenic nerve palsy occurred after anterior decompression and fusion for cervical OPLL. Bilateral phrenic nerve palsy was diagnosed radiographically: postoperative chest radiograph showed bilateral laxity of the diaphragm. Movement of the bilateral diaphragm appeared 3 weeks after surgery. The patient successfully returned to normal daily life after ventilatory support for 3 months, although nocturnal oxygen support was still necessary at the latest follow-up, 3 years after surgery. The possible causes of this complication include bilateral C4 nerve root stretching, iatrogenic injury of the gray matter in the ventral horn, alteration of blood circulation related to spinal edema, or re-impingement on the spinal cord at the cranial part of the decompression site.

CONCLUSIONS

Bilateral phrenic nerve palsy occurred after anterior decompression and fusion for cervical OPLL. Bilateral phrenic nerve palsy should be kept in mind as a serious complication of spinal surgery. It should be considered when patients unexpectedly fail to wean from the ventilator after surgery.

The anatomic relation among the nerve roots, intervertebral foramina, and intervertebral discs of the cervical spine

STUDY DESIGN

An anatomic study of the cervical intervertebral foramina, nerve roots, and intradural rootlets performed using a surgical microscope.

OBJECTIVES

To investigate the anatomy of cervical root compression, and to obtain the anatomic findings related to cervical foraminotomy for the treatment of cervical radiculopathy.

SUMMARY OF BACKGROUND DATA

Cervical foraminotomy is a procedure performed frequently for the management of cervical radiculopathy. However, anatomic studies of cervical foraminotomy have not been fully elucidated.

METHODS

In this study, 18 cadavers were obtained for the study of the cervical spine. All the soft tissues were dissected from the cervical spine. Thereafter, laminectomy and facetectomy were performed on C4 through T1 using a surgical microscope. The nerve roots and surrounding anatomic structures, including intervertebral discs and foramina, were exposed. In addition, the intradural rootlets and their intersegmental connections were observed.

RESULTS

The shape of the intervertebral foramina approximated a funnel, the entrance zone being the most narrow part and the root sleeves conical, with their takeoff points from the central dural sac being the largest part. Therefore, compression of the nerve roots occurred at the entrance zone of the intervertebral foramina. Anteriorly, compression of the nerve roots was caused by protruding discs and osteophytes of the uncovertebral region, whereas the superior articular process, the ligamentum flavum, and the periradicular fibrous tissues affected the nerve posteriorly. The C5 nerve roots were found to exit over the middle aspect of the intervertebral disc, whereas the C6 and C7 nerve roots were found to traverse the proximal part of the disc. The C8 nerve roots had little overlap with the C7-T1 disc in the intervertebral foramen. The C6 and C7 rootlets passed two disc levels in the dural sac. Also, a high incidence of the intradural connections between the dorsal rootlets of C5, C6, and C7 segments was found.

CONCLUSIONS

This study demonstrated the anatomy of the nerve roots, rootlets, and intervertebral foramina, and may aid in understanding the pathology of cervical radiculopathy. The presence of intradural connections between dorsal nerve roots and the relation between the course of the nerve root and the intervertebral disc may explain the clinical variation of symptoms resulting from-nerve root compression in the cervical spine. To perform cervical foraminotomy for cervical radiculopathy, it is necessary to understand the detailed anatomy of the intervertebral foramina thoroughly.

Microsurgical anatomy of the dorsal cervical nerve roots and the cervical dorsal root ganglion/ventral root complexes

BACKGROUND

It is known that a "dissociated motor loss" of the deltoid muscle can occur with disconcerting frequency after cervical spine surgery. The etiology of this entity is in question. We conducted an anatomic study to identify anatomic factors that might predispose C5 to injury.

METHODS

We studied 128 dorsal cervical nerves and root ganglion/ventral root complexes in 10 adult cadavers. At each cervical level the following data were recorded: number of rootlets, range of width of rootlets, length of DREZ, cranial angles of the superior and inferior rootlets with the spinal cord, length of the superior and inferior rootlets, dimensions of the foramina, dimensions of the dorsal root, dimensions of the dorsal root ganglion (DRG)/ventral root (VR) complex, and the blood supply to the DRG. The histology at the site of compression was also examined. Statistical analysis was conducted using the single factor-repeated measures analysis of variance.

RESULTS

We found that, 1) the C5 superior dorsal rootlets angle less inferiorly from the cervical cord than the other dorsal cervical roots (p=0.001), 2) the majority of the DRG/VR complexes from C3 to C6 were compressed by the vertebral artery (73%), 3) the C5 DRG/VR complex was compressed to the greatest extent (77.6%, p=0.3519), and 4) the ganglionic artery was more frequent at C4, C5, and C6.

CONCLUSION

To our knowledge, the second finding has not been reported previously. The first and third findings may help explain why C5 is more vulnerable to injury.

Anterior cervical corpectomy for cervical spondylotic myelopathy

OBJECTIVE

To evaluate the efficacy of anterior surgery for the treatment of cervical spondylotic myelopathy, we have reviewed our experience with anterior cervical corpectomy (ACC) at the University of Florida, specifically analyzing neurological outcomes and complications. These results have been compared with historical control subjects receiving laminectomy or "no treatment."

METHODS

Between 1982 and 1992, 93 ACC operations were performed for the primary diagnosis of cervical spondylotic myelopathy. This consecutive series of patients was reviewed retrospectively. Age, gender, pre- and postoperative myelopathy severity, number of levels decompressed, and neurological complications were assessed. Myelopathy severity was graded using the Nurick myelopathy grading system. The average follow-up period was 39 months (range, 2-137 mo).

RESULTS

Symptomatic improvement was achieved for 92% of patients (F = 28.9, df = 2172, P < 0.001). Nurick scores reflected improvement for 86% of patients, with the conditions of 13% remaining unchanged and only one patient showing worsening. Preoperative myelopathy severity was weakly correlated with age (P < 0.05) but was not correlated with gender or number of levels decompressed. Similarly, postoperative myelopathy severity was not significantly correlated with age, gender, preoperative myelopathy severity, or number of levels decompressed. ACC-treated patients showed an average improvement of 1.24 points on the Nurick scale, compared with an improvement of 0.07 points for patients treated with laminectomy (P < 0.001) and a deterioration of 0.23 points for patients undergoing conservative treatment (P < 0.001). Complications were slightly more likely to occur in older patients (P < 0.05). The number of levels decompressed was not significantly correlated with complications. Only one permanent neurological complication was seen in this series of patients.

CONCLUSION

We conclude that ACC is a safe and effective treatment for cervical spondylotic myelopathy. In an average of 39 months, ACC showed improved results in terms of myelopathy scores, compared with historical control subjects receiving either no treatment or laminectomy. Age, gender, preoperative myelopathy severity, and extent of disease were not negative predictors of clinical outcomes.

Regression of cervical disc herniation observed on magnetic resonance images

STUDY DESIGN

A retrospective study of cervical disc herniation using results of repeated magnetic resonance imaging examinations.

OBJECTIVES

To clarify the cervical disc herniation morphological changes over time in order to establish a strategy for treatment.

SUMMARY OF BACKGROUND DATA

In the authors' previous magnetic resonance imaging follow-up study of patients with lumbar disc herniation, spontaneous regression was observed in the sequestration-type lesions, and it was found that the tendency toward regression differed based on the anatomic position of extruded disc material.

METHODS

Thirty-eight patients with cervical disc herniation who underwent repeated magnetic resonance imaging examinations were studied. The changes over time in herniated disc size were evaluated using this imaging technique. Evaluation showed the characteristics of those in whom spontaneous regression was found, such as extrusion pattern, and the clinical outcome was evaluated by symptoms.

RESULTS

In 15 patients (40%), the volume of herniated material was decreased. The interval from onset of symptoms to the initial examination was significantly shorter in the regression group than in the group that showed no change in disc herniation. By extrusion pattern, cervical disc herniation, which was divided into migration type on sagittal view and lateral type on axial view, most frequently exhibited spontaneous regression. All of the patients with radicular pain and upper limb amyotrophy were treated successfully with conservative therapy.

CONCLUSION

Although the possibility of the combination of hemorrhage and disc material could not be denied, active resorption of herniated material probably occurred during the acute phase. Extruded material exposed to the epidural space may be resorbed more quickly than that beneath the ligament. Vascular supply probably plays a role in the mechanism of resorption. The phase and position of extrusion were the significant factors affecting cervical disc herniation resorption. It was demonstrated that examination performed during the acute phase using magnetic resonance imaging is necessary for elucidation of the pathogenesis of cervical disc herniation, and that migrating, lateral-type herniations regress so frequently that conservative treatment should be chosen not only for patients with radicular pain, but also for those with upper limb amyotrophy.