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

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.

Multivariate analysis of factors associated with spinal cord area in single-door cervical laminoplasty with miniplate fixation

Objectives

To explore the factors associated with the increased spinal cord area in single-door cervical laminoplasty (SDCL) with miniplate fixation.

Methods

A retrospective study enrolled 83 patients underwent SDCL with miniplate fixation and the patient characteristics such as age, gender, tobacco use, alcohol use, diabetes mellitus, hypertension, diagnosis, operative level, etc., were obtained. The opening angle, door shaft position and spinal canal area of the patients were measured after surgery. The sagittal canal diameter (SCD), the C2–7 Cobb angle, the cervical curvature index (CCI), the range of motion (ROM) and the spinal canal area were measured before and after operation. The increased cervical spinal cord area was also measured before and after surgery, and the correlation between the above indicators and the increased cervical spinal cord area was studied through Pearson’s correlation analysis and multivariate logistic regression analysis.

Results

There were 34 patients in small spinal cord area increment group (SAI group), 29 patients in middle spinal cord area increment group (MAI group) and 20 patients in large spinal cord area increment group (LAI group). The preoperative diagnosis(P = 0.001), door shaft position (P = 0.008), preoperative spinal canal area (P = 0.004) and postoperative spinal canal area (P = 0.015) were significant different among the 3 groups. The multivariate analysis showed that the preoperative diagnosis (OR = 2.076, P = 0.035), door shaft position (OR = 3.425, P = 0.020) and preoperative spinal canal area (OR = 10.217, P = 0.009) were related to increased spinal cord area.

Conclusions

The preoperative diagnosis, door shaft position and preoperative spinal canal area might be associated with increased spinal cord area after cervical laminoplasty with miniplate fixation. Preoperative symptoms are mostly caused by compression of the spinal cord, so spinal cord area enlargement can bring a better recovery in patients alongside long-term. Spine surgeons should pay more attention to the accuracy of the preoperative diagnosis, the preoperative measurement of spinal canal area and the door shaft position during the operation.

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.