Positions of dorsal root ganglia in the cervical spine. An anatomic and clinical study

Efficacy and Safety of Cervical and High-Thoracic Dorsal Root Ganglion Stimulation Therapy for Complex Regional Pain Syndrome of the Upper Extremities

OBJECTIVES

The purpose of this study was to evaluate analgesic and safety considerations for high thoracic and cervical dorsal root ganglion (DRG) neuromodulation for complex regional pain syndrome (CRPS). We hypothesized that DRG neuromodulation would provide sustained analgesia with complications like that of low thoracic or lumbar electrode implantation.

MATERIALS AND METHODS

A single-center, retrospective study was conducted of patients with CRPS I or II of the upper extremities, refractory to previous therapies, who were treated with DRG neuromodulation in the upper thoracic and cervical spine. The primary outcome was successful DRG therapy, defined as ≥ 50% pain relief on a Numeric Rating Scale (NRS) 0 to 10 pain scale at six months after implantation. A secondary outcome was a reduction in daily opioid use after DRG therapy.

RESULTS

After a DRG stimulation trial, 17 of 20 patients (85%) had ≥ 50% improvement in NRS pain and underwent a permanent pulse generator implant, with 100% endorsing ≥ 50% pain relief at six months. Mean NRS pain scores before DRG neuromodulation were 9.3 ± 1.1, with a mean reduction of 5.5 (95% CI, 4.5-6.6; p < 0.001) at six months. Ten patients were taking opioids at baseline; the median (interquartile range) dose was 45 mg (23 to 120) morphine equivalents (MME), which was reduced to 20 MME (15 to 40) at six months. The median reduction in daily MME use was -25 (95% CI, -100 to 20; p = 0.099). Six of 20 patients (30%) experienced a complication: three had lead migration; two experienced paresthesias; and one had a reduction in shoulder mobility. One patient had symptoms of a reversible spinal cord compression immediately after implant, requiring emergent electrode removal.

CONCLUSIONS

DRG neuromodulation for patients with CRPS of the upper extremities produced clinically important analgesia and reduced opioid use for ≥ six months but was associated with one serious complication.

2. Cervical radicular pain

INTRODUCTION

Cervical radicular pain is pain perceived in the upper limb, caused by irritation or compression of a cervical spine nerve, the roots of the nerve, or both.

METHODS

The literature on the diagnosis and treatment of cervical radicular pain was retrieved and summarized.

RESULTS

The diagnosis is made by combining elements from the patient's history, physical examination, and supplementary tests. The Spurling and shoulder abduction tests are the two most common examinations used to identify cervical radicular pain. MRI without contrast, CT scanning, and in some cases plain radiography can all be appropriate imaging techniques for nontraumatic cervical radiculopathy. MRI is recommended prior to interventional treatments. Exercise with or without other treatments can be beneficial. There is scant evidence for the use of paracetamol, nonsteroidal anti-inflammatory drugs, and neuropathic pain medications such as gabapentin, pregabalin, tricyclic antidepressants, and anticonvulsants for the treatment of radicular pain. Acute and subacute cervical radicular pain may respond well to epidural corticosteroid administration, preferentially using an interlaminar approach. By contrast, for chronic cervical radicular pain, the efficacy of epidural corticosteroid administration is limited. In these patients, pulsed radiofrequency treatment adjacent to the dorsal root ganglion may be considered.

CONCLUSIONS

There is currently no gold standard for the diagnosis of cervical radicular pain. There is scant evidence for the use of medication. Epidural corticosteroid injection and pulsed radiofrequency adjacent to the dorsal root ganglion may be considered. [Correction added on 12 June 2023, after first online publication: The preceding sentence was corrected.].

Recent Advancements in Epidural Etanercept for Pain Management in Radiculopathy: A Literature Review

The most common etiology of low back and neck pain is associated with spinal cord pathologies. Regardless of origin, low back and neck pain are some of the most common causes of disability worldwide. Mechanical compression due to spinal cord diseases, such as degenerative disc disorders, can lead to radiculopathy, which manifests as numbness or tingling and can progress to loss of muscle function. Conservative management, such as physical therapy, has not been proven effective in treating radiculopathy, and surgical treatments have more risks than benefits for most patients. Epidural disease-modifying medications, such as Etanercept, have been recently explored due to their minimal invasiveness and direct effects on inhibiting tumor necrosis factor-α (TNF-α). Therefore, this literature review aims to evaluate epidural Etanercept's effect on radiculopathy caused by degenerative disc diseases. Epidural Etanercept has been shown to improve radiculopathy in patients with lumbar disc degeneration, spinal stenosis, and sciatica. Further research is needed to compare the effectiveness of Etanercept with commonly used treatments such as steroids and analgesia.

Electrodiagnostic Studies in Degenerative Cervical Myelopathy

The diagnosis of degenerative cervical myelopathy can generally be made with a thorough history, physical examination, and spinal imaging. Electrodiagnostic studies, consisting of nerve conduction studies and electromyography, are a useful adjunct when the clinical picture is inconsistent or there is concern for overlapping pathology. Electrodiagnostic studies may be particularly helpful in identifying cases of myeloradiculopathy, when there is combined nerve root and spinal cord injury, both with regards to prognosis and guiding surgical treatment. Electrodiagnostic studies are a useful adjunct for the spine surgeon and should be used when there are features atypical for degenerative cervical myelopathy or when there is suspicion for a concomitant disease process.

Evaluation of Dynamic Foraminal Stenosis with Positional MRI in Patients with C6 Radiculopathy-Mimicking Pain: A Prospective Radiologic Cohort Study

Objective

Patients with a C6 radiculopathy-mimicking complaint are always in the gray zone if the diagnosis is not clear. The aim of the study is to make the diagnosis clear if the neck and shoulder pain is caused by a dynamic stenosis of the neural foramen at the C5-C6 level.

Methods

Patients with a C6 radiculopathy-mimicking complaint were included in the study. Patients had a cervical spine magnetic resonance imaging (MRI) at the normal limits, or a minimal protrusion at the C5-C6 level underwent a dynamic MRI procedure. We measured the foraminal area and spinal cord diameter (SCD) at the C5-C6 level by using the PACS system ROI irregular are determination integral embedded to PACS. Inter- and intraobserver reliability of measurements was evaluated. Results were analyzed statistically, and a p value< 0.05 was accepted as statistically meaningful.

Results

A total of 23 patients between January 2019 and June 2019 were included in the study. There were 10 men and 13 women, and the mean age was 41.3 (range 33-53). Foraminal area decrease at C5-C6 in extension and increase in flexion when compared with the neutral position was statistically significant (p < 0.001). Foraminal area changes between the complaint side and the opposite side was not statistically different (p > 0.05). Interobserver and intraobserver reliability of measurements were classified as in almost perfect agreement.

Conclusions

Our present work presented dynamic and positional foraminal changes in MRI with radiculopathy-mimicking patients. Soever, we did not find a difference between the clinical complaint side and the opposite side in radiculopathy-mimicking patients. Cervical radiculopathy pain should not be attributed only to foraminal sizes. PACS embedded irregular area measurement integral allows the easy measure of a big number of patients without additional set-up and digital work requirements.

Electrodiagnostic Assessment of Radiculopathies

This article discusses the electrodiagnostic assessment of radiculopathy. Relevant anatomy initially is reviewed followed by discussion surrounding the approach to nerve conduction studies and needle electrode examination when it comes to radiculopathy evaluation. Pitfalls of the electrodiagnosis versus clinical diagnosis of radiculopathy and the definitions of acute versus chronic, and active versus inactive, are reviewed.

A Literature Review of Dorsal Root Entry Zone Complex (DREZC) Lesions: Integration of Translational Data for an Evolution to More Accurate Nomenclature

The purpose of this translational review was to provide evidence to support the natural evolution of the nomenclature of neuromodulatory and neuroablative radiofrequency lesions for pain management from lesions of individualized components of the linear dorsal afferent pathway to “Dorsal Root Entry Zone Complex (DREZC) lesions.” Literature review was performed to collate anatomic and procedural data and correlate these data to clinical outcomes. There is ample evidence that the individual components of the DREZC (the dorsal rami and its branches, the dorsal root ganglia, the dorsal rootlets, and the dorsal root entry zone) vary dramatically between vertebral levels and individual patients. Procedurally, fluoroscopy, the most commonly utilized technology is a 2-dimensional x-ray-based technology without the ability to accurately locate any one component of the DREZC dorsal afferent pathway, which results in clinical inaccuracies when naming each lesion. Despite the inherent anatomic variability and these procedural limitations, the expected poor clinical outcomes that might follow such nomenclature inaccuracies have not been shown to be prominent, likely because these are all lesions of the same anatomically linear sensory pathway, the DREZC, whereby a lesion in any one part of the pathway would be expected to interrupt sensory transmission of pain to all subsequent more proximal segments. Given that the common clinically available tools (fluoroscopy) are inaccurate to localize each component of the DREZC, it would be inappropriate to continue to erroneously refer to these lesions as lesions of individual components, when the more accurate “DREZC lesions” designation can be utilized. Hence, to avoid inaccuracies in nomenclature and until more accurate imaging technology is commonly utilized, the evidence herein supports the proposed change to this more sensitive and inclusive nomenclature, “DREZC lesions.”

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Multicenter Retrospective Analysis of Dorsal Root Ganglion Stimulator Placement Using Intraoperative Neuromonitoring in Asleep Patients During Early Periods of Adoption

OBJECTIVES

Intraoperative neuromonitoring (IONM) has been used in the implantation of spinal cord stimulation for both safety and confirmation of lead placement. It is less well defined in its use for dorsal root ganglion (DRG) stimulator placement.

MATERIALS AND METHODS

This is a retrospective analysis of 304 leads placed in 93 patients undergoing DRG stimulation therapy with its placement utilizing IONM in asleep patients by four implanting physicians in four separate centers. The first year, or early adoption period, of placements for each site was chosen as the included cases to evaluate.

RESULTS

There were a total of 14 IONM alerts across the 304 lead placements. There were two complications, no permanent or severe adverse events, and no revisions. All alerts led to a change in approach as a corrective action. The two complications were a patient requiring a blood patch for an undetected CSF leak, while the other was a generator site seroma that resolved with conservative care. A single patient experienced transient calf paresthesia's in the post-operative period.

CONCLUSION

This retrospective series demonstrates the utility and accuracy of IONM in not only confirming proper dorsal placement of a DRG electrode but also in maintaining a low adverse event profile. It further demonstrates that its utility in the real world with new users can be safe and accurate with an ease of integration.

A Prospective Analysis of the Use of Intraoperative Neuromonitoring for Mapping the S1 Dorsal Root Ganglion Location to Determine Ideal Lead Positioning and Predict Postoperative Programming

INTRODUCTION

The location of the sacral dorsal root ganglion (DRG) is variable and can range from a location in the canal to the foramen. It is therefore imperative to not only ensure a dorsal placement but also map the location of the DRG.

MATERIALS AND METHODS

This is a prospective analysis of the use of intraoperative neuromonitoring (IONM) being utilized in asleep patients to map the location of the S1 DRG with somatosensory evoked potential (SSEP) and electromyogram (EMG) thresholds, as well as comparing this with postoperative programming. These observations were then correlated with the position of the electrode contacts relative to the sacral border. It was performed in a single center with 12 lead placements in eight patients.

RESULTS

The IONM demonstrated that EMG thresholds decrease or stay the same as you stimulate more distal on the lead. Sensory signals are generated the majority of the time either proximal or on the sacral border. Postoperative programming correlated with the mapped location of the DRG on IONM, which was either posterior or on the sacral border. There was a single lead in which the IONM confirmed DRG location on the distal contact, which was anterior to the sacral border, and also correlated with postoperative programming.

CONCLUSIONS

This prospective analysis further demonstrates the utility and accuracy of IONM. The use of DRG IONM is reliable for confirming dorsal placement along the S1 DRG, mapping its position, and guiding postoperative programming. The S1 DRG is located at the border of the foramen and canal in most, but not all cases.

Hyperthermia associated with spinal radiculopathy as determined by digital infrared thermographic imaging

In general, in digital infrared thermographic imaging (DITI) of patients with unilateral spinal radicular pain, the thermal pattern of the extremities of the side of lesion shows hypothermia compared to the opposite, intact side. However, sometimes, DITI shows hyperthermia on the side of the lesion, and this variation can cause confusion. We compared the data of both hypothermia and hyperthermia patients to clarify the factors determining different thermal characteristics in spinal radiculopathy.We retrospectively collected data from patients who underwent DITI at a single center. The final cohort (n = 224) was allocated into 2 groups, a hypothermia group (n = 180) or a hyperthermia group (n = 44). We compared the various factors, including demographic factors and symptom-related factors, that might affect the results of DITI.Except the presence of trauma history (13.9% vs 31.8%, odds ratio 2.893, P = .008), no significant intergroup difference was found in baseline demographic factors, including age, gender, diabetes mellitus, spinal level of pathology, and intervention history. Among symptom-related factors, in the hyperthermia group, the symptom duration was shorter (10.64 weeks [95% confidence interval (CI) 8.36-13.04] vs 2.10 weeks [95% CI 1.05-3.53], P < .001) and Visual Analogue Scale (VAS) of radicular pain was higher (4.23 ± 1.29 vs 5.18 ± 1.40, P < .001) than in the hypothermia group. Also, in the regression analysis, significant factors for hyperthermia include the presence of trauma history, shorter symptom duration (cut-off value 2.50 weeks or less) and higher VAS of radicular pain (cut-off value 4.50 or more).In patients with trauma history, acute phase, and severe radicular pain, hyperthermia in DITI is not unusual and careful interpretation of the DITI results is necessary for proper diagnosis and treatment decisions in spinal radiculopathy.

Human Dorsal Root Ganglia

Sensory neurons with cell bodies situated in dorsal root ganglia convey information from external or internal sites of the body such as actual or potential harm, temperature or muscle length to the central nervous system. In recent years, large investigative efforts have worked toward an understanding of different types of DRG neurons at transcriptional, translational, and functional levels. These studies most commonly rely on data obtained from laboratory animals. Human DRG, however, have received far less investigative focus over the last 30 years. Nevertheless, knowledge about human sensory neurons is critical for a translational research approach and future therapeutic development. This review aims to summarize both historical and emerging information about the size and location of human DRG, and highlight advances in the understanding of the neurochemical characteristics of human DRG neurons, in particular nociceptive neurons.

Finding the "Sweet Spot" for C2 Root Transection in C1 Lateral Mass Exposure

BACKGROUND

Atlantoaxial fusion often requires C2 nerve transection for complete C1 lateral mass exposure. Nerve transection is made ideally at the preganglionic segment proximal to the dorsal root ganglion to minimize the risk of postoperative dysesthesias. If the nerve is transected too proximally, cerebrospinal fluid leak may be encountered by violation of the dura and arachnoid where the sensory and motor nerve rootlets exit the subarachnoid space. In this study we aimed to quantify the length of the C2 nerve preganglionic segment using cadaveric specimens and develop a method for reliable intraoperative localization for sectioning during C1-2 arthrodesis.

METHODS

Using microsurgical techniques, 16 C2 nerves from 8 frozen and injected cadaveric cervical spine specimens were dissected. Two key measurements were taken to establish a reliable method of preganglionic segment identification. The "sweet spot" for nerve transection was based on the approximate location of the midpoint of the preganglionic segment.

RESULTS

The final determination of the ideal spot for C2 nerve transection using these calculations was 3 mm lateral to the medial border of the lateral mass.

CONCLUSIONS

This anatomic study found remarkable consistency in the preganglionic segment length. The medial border of the lateral mass appeared to be a consistently reliable landmark for identification of the preganglionic segment of the C2 nerve root. By using relationships between known anatomic structures intraoperatively, safety of atlantoaxial fixation can be optimized to maximize complication avoidance and satisfactory patient outcomes.

The Neuromodulation Appropriateness Consensus Committee on Best Practices for Dorsal Root Ganglion Stimulation

INTRODUCTION

The Neuromodulation Appropriateness Consensus Committee (NACC) is dedicated to improving the safety and efficacy of neuromodulation and thus improving the lives of patients undergoing neuromodulation therapies. With continued innovations in neuromodulation comes the need for evolving reviews of best practices. Dorsal root ganglion (DRG) stimulation has significantly improved the treatment of complex regional pain syndrome (CRPS), among other conditions. Through funding and organizational leadership by the International Neuromodulation Society (INS), the NACC reconvened to develop the best practices consensus document for the selection, implantation and use of DRG stimulation for the treatment of chronic pain syndromes.

METHODS

The NACC performed a comprehensive literature search of articles about DRG published from 1995 through June, 2017. A total of 2538 article abstracts were then reviewed, and selected articles graded for strength of evidence based on scoring criteria established by the US Preventive Services Task Force. Graded evidence was considered along with clinical experience to create the best practices consensus and recommendations.

RESULTS

The NACC achieved consensus based on peer-reviewed literature and experience to create consensus points to improve patient selection, guide surgical methods, improve post-operative care, and make recommendations for management of patients treated with DRG stimulation.

CONCLUSION

The NACC recommendations are intended to improve patient care in the use of this evolving therapy for chronic pain. Clinicians who choose to follow these recommendations may improve outcomes.

Ultrasonography has a diagnostic value in the assessment of cervical radiculopathy: A prospective pilot study

OBJECTIVE

This study investigated the diagnostic accuracy of the difference in the cross-sectional areas (CSAs) of affected cervical nerve roots (NRs) for diagnosing cervical radiculopathy (CR).

METHODS

In total, 102 CR patients and 219 healthy volunteers were examined with ultrasound. The CSA of the cervical NR at each level was measured on the affected side and the contralateral side in CR patients by blinded ultrasonographic technicians. The difference between the CSAs of CR patients and normal volunteers and the difference in the laterality of CSA at the same affected level (ΔCSA) were calculated for each cervical level.

RESULTS

The CSAs of the affected NRs in CR patients were significantly larger than those of the unaffected NRs in CR patients and those of the control group at the C5, C6 and C7 levels (P<0.005). ΔCSA was also significantly larger in the CR group at all levels (P<0.001). A receiver operating characteristic analysis demonstrated that the threshold values were 9.6 mm² (CSA) for C5NR and 15 mm² for both C6NR and C7NR.

CONCLUSIONS

This study revealed that the CSAs of affected NRs were enlarged and that the laterality of the CSA (ΔCSA) was greater in CR patients than in control patients.

KEY POINTS

• Cervical radiculopathy is diagnosed through ultrasonographic measurement of the CSAs. • The CSAs of affected nerve roots were significantly enlarged. • The ΔCSA in the CR group was significantly higher than in the control group. • Diagnostic CSA and ΔCSA thresholds were identified.

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.

Clinical relevance of neuroforaminal patency after anterior cervical discectomy and fusion

BACKGROUND

We sought to investigate the clinical relevance of neuroforaminal patency and facet degeneration one year after anterior cervical discectomy and fusion (ACDF). Previous studies were characterized by imprecise techniques and fragmentary measurements, and most lacked reliable clinical data and correlation analyses.

METHODS

Patients with cervical mono- or bi-level degenerative pathology were prospectively included. Neuroforaminal size and segmental height were determined quantitatively, and the degree of facet degeneration was assessed qualitatively before and one year after the operation, by computed tomography. Clinical data, such as the severity of neck and arm pain, were assessed on a visual analogue scale (VAS) from 0 to 10, and neck disability index (NDI) was recorded before and one year after the operation. Their correlation with radiological data was investigated.

RESULTS

Seventy-nine patients aged 53.3 ± 11.3 years were included. One year after surgery, median VAS pain intensity was still significantly improved (neck, from 5 to 1; right arm, from 2 to 1; left arm, from 4 to 1) as was NDI (from 40 to 20). Neuroforaminal size showed a reduction on both sides (left, 0.0289 ± 0.09 cm(2); right, 0.0149 ± 0.08 cm(2)). One year after the operation, segmental height decreased and facet degeneration increased from measures taken before the operation. No correlations were found between neuroforaminal stenosis or the degree of facet degeneration and various clinical outcome parameters.

CONCLUSIONS

The decrease in segmental height one year after ACDF leads in turn to secondary neuroforaminal stenosis and progressive facet degeneration. Of the various neuroforaminal variables used, none revealed a threshold value indicative of the presence or severity of radicular arm pain. This absence of correlation between imaging and clinical information is important and should be considered when allocating patients for surgical interventions.

The Electrodiagnosis of Cervical and Lumbosacral Radiculopathy

This article reviews the usefulness of the electrodiagnostic examination in patients who have suspected cervical and lumbosacral radiculopathy. This study can verify the presence and severity of radiculopathy, determine which levels are involved, and provide an electrodiagnostic correlate to imaging abnormalities. A practical approach for conducting the nerve conduction portion and needle electrode examination in these patients is discussed.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited

OBJECTIVE

The objectives of this white paper are to review and summarize the basic science literature relevant to spinal fixation (subluxation) and spinal adjusting procedures and to make specific recommendations for future research.

METHODS

PubMed, CINAHL, ICL, OSTMED, and MANTIS databases were searched by a multidisciplinary team for reports of basic science research (since 1995) related to spinal fixation (subluxation) and spinal adjusting (spinal manipulation). In addition, hand searches of the reference sections of studies judged to be important by the authors were also obtained. Each author used key words they determined to be most important to their field in designing their individual search strategy. Both animal and human studies were included in the literature searches, summaries, and recommendations for future research produced in this project.

DISCUSSION

The following topic areas were identified: anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system. A relevant summary of each topic area and specific recommendations for future research in each area were the primary objectives of this project.

CONCLUSIONS

The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.

Head-turned rear impact causing dynamic cervical intervertebral foramen narrowing: implications for ganglion and nerve root injury

OBJECT

A rotated head posture at the time of vehicular rear impact has been correlated with a higher incidence and greater severity of chronic radicular symptoms than accidents occurring with the occupant facing forward. No studies have been conducted to quantify the dynamic changes in foramen dimensions during head-turned rear-impact collisions. The objectives of this study were to quantify the changes in foraminal width, height, and area during head-turned rear-impact collisions and to determine if dynamic narrowing causes potential cervical nerve root or ganglion impingement.

METHODS

The authors subjected a whole cervical spine model with muscle force replication and a surrogate head to simulated head-turned rear impacts of 3.5, 5, 6.5, and 8 G following a noninjurious 2-G baseline acceleration. Continuous dynamic foraminal width, height, and area narrowing were recorded, and peaks were determined during each impact; these data were then statistically compared with those obtained at baseline. The authors observed significant increases (p < 0.05) in mean peak foraminal width narrowing values greater than baseline values, of up to 1.8 mm in the left C5-6 foramen at 8 G. At the right C2-3 foramen, the mean peak dynamic foraminal height was significantly narrower than baseline when subjected to rear-impacts of 5 and 6.5 G, but no significant increases in foraminal area were observed. Analysis of the results indicated that the greatest potential for cervical ganglion compression injury existed at C5-6 and C6-7. Greater potential for ganglion compression injury existed at C3-4 and C4-5 during head-turned rear impact than during head-forward rear impact.

CONCLUSIONS

Extrapolation of present results indicated potential ganglion compression in patients with a non-stenotic foramen at C5-6 and C6-7; in patients with a stenotic foramen the injury risk greatly increases and spreads to include the C3-4 through C6-7 as well as C4-5 through C6-7 nerve roots.

Dynamic intervertebral foramen narrowing during simulated rear impact

STUDY DESIGN

A biomechanical study of intervertebral foraminal narrowing during simulated automotive rear impacts.

OBJECTIVES

To quantify foraminal width, height, and area narrowing during simulated rear impact, and evaluate the potential for nerve root and ganglion impingement in individuals with and without foraminal spondylosis.

SUMMARY OF BACKGROUND DATA

Muscle weakness and paresthesias, documented in whiplash patients, have been associated with neural compression within the cervical intervertebral foramen. To our knowledge, no studies have comprehensively examined dynamic changes in foramen dimensions.

METHODS

There were 6 whole cervical spine specimens (average age 70.8 years) with muscle force replication and surrogate head that underwent simulated rear impact at 3.5, 5, 6.5, and 8 g, following noninjurious baseline 2 g acceleration. Peak dynamic narrowing of foraminal width, height, and area were determined during each impact and statistically compared to baseline narrowing.

RESULTS

Significant increases (P < 0.05) in average peak foraminal width narrowing above baseline were observed at C5-C6 beginning with 3.5 g impact. No significant increases in average peak foraminal height narrowing were observed, while average peak foraminal areas were significantly narrower than baseline at C4-C5 at 3.5, 5, and 6.5 g.

CONCLUSIONS

Extrapolation of the present results indicated that the highest potential for ganglia compression injury was at the lower cervical spine, C5-C6 and C6-C7. Acute ganglia compression may produce a sensitized neural response to repeat compression, leading to chronic radiculopathy following rear impact.

Morphologic changes in the cervical neural foramen due to flexion and extension: in vivo imaging study

STUDY DESIGN

Dimensional measurement of cervical neural foramen at various positions, using reformatted computed tomography.

OBJECTIVES

To examine the morphologic changes in the neural foramen during flexion and extension of the cervical spine in vivo.

SUMMARY OF BACKGROUND DATA

Previous cadaveric studies have shown the effect of cervical spinal motion on dimensions of the neural foramen. However, little information is available about dynamic morphologic changes in the cervical neural foramen in vivo.

METHODS

Cervical CT images of seven healthy volunteers were taken at the neutral position, maximum extension, and maximum flexion, and were reconstructed in the oblique plane perpendicular to the long axis of each neural foramen from the C3-C4 to C6-C7 level. Measured parameters included foraminal height, width, cross-sectional area, and segmental sagittal rotation at each spinal level. Differences in neural foraminal dimensions among these positions were analyzed. Correlations of segmental sagittal rotation with differences in dimensions between flexion and extension were analyzed.

RESULTS

Flexion significantly increased the foraminal height (by 1.0 mm; 11%), foraminal width (by 1.0 mm; 16%), and foraminal area (by 12 mm2; 28%) (P < 0.01). Extension significantly decreased the foraminal height (by 0.9 mm; 10%), foraminal width (by 1.4 mm; 22%), and foraminal area (by 8.0 mm2; 17%) (P < 0.01). Segmental sagittal rotation significantly positively correlated with % change in foraminal height (r = 0.434, P < 0.01) and area (r = 0.504, P < 0.01).

CONCLUSIONS

The present results are consistent with those of previous in vitro studies and may explain the clinical observation that cervical extension aggravates symptoms in patients with cervical radiculopathy and that flexion often relieves them.

Segmental degeneration in the cervical spine and associated changes in dorsal root ganglia

Degenerative change in cervical segments C5-C7 was documented to determine whether osteo-ligamentous adaptations were age-related. In addition, companion morphological studies were carried out to determine whether parallel changes occurred in related soft tissues, including DRG. Independent of the provoking stimulus, aberrant soft tissue change may be expected with segmental degeneration. Two associations were identified: between the incidence of segmental degeneration and severity of DRG distortion, and between segmental degeneration and DRG inflammatory mast cell density. Peripheral type C cells seemed more susceptible to compression in circumstances of DRG distortion. In light of neuropeptide expression in these cell types, predominant type C cell compression may be clinically relevant in the noxious cascade contributing to the sensation of pain.

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.

Electrodiagnostic approach to the patient with suspected radiculopathy

Cervical and lumbosacral radiculopathies are among the most common causes of referral to the electromyographic (EMG) laboratory. Among all the other electrodiagnostic studies (nerve conduction studies, late responses, somatosensory evoked potentials, root electrical and magnetic stimulation studies), the needle electrode (needle EMG) examination is the most specific and sensitive. A good grasp of the anatomic, clinical and electromyographic myotomal charts is essential to localize radiculopathies to single (or more) root lesions.

Electrophysiology of radiculopathies

The anatomy, pathophysiology, and clinical evaluation of radiculopathies are discussed. Defining whether root injury is present and which roots are involved can be difficult but critical for patient management. In conjunction with clinical and radiological information, studies that establish physiological abnormalities of roots should be helpful and important. Clinical neurophysiological studies for radiculopathies are performed frequently but have yet to achieve a universally accepted role in the evaluation of these patients. Electrophysiological techniques for the evaluation of radiculopathies are reviewed. Needle electromyography is the best established of these procedures but has the disadvantage of requiring injury to motor fibers of both a certain degree and distribution. Nerve conduction studies may rarely be abnormal in radiculopathies but are needed to be certain other conditions that may produce similar symptoms and signs are not present. H reflexes and F waves probably have roles in the evaluation of radiculopathies but published reports about F waves in radiculopathies have been marred by inadequate methodology. There is evidence based on large series of patients that somatosensory evoked potentials can be helpful for evaluating patients with multilevel injury such as spinal stenosis, patients where electrophysiological studies may have their greatest clinical utility. Further work using either electrical stimulation with needles or magnetic stimulation of roots seems warranted. The demonstration of meaningful electrophysiological changes with activities that reproduce radicular symptoms may be a promising experimental approach. Available information does not necessarily answer critical questions about the role of electrophysiology in patients with radiculopathies. This cannot be done using analyses based on current ideas about evidence based medicine given the absence of a 'gold standard' for defining radiculopathies as well the absence of blinded studies. The available information provides strong arguments for further investigations evaluating different clinical neurophysiological techniques in the same patient, and for evaluating the value of these techniques by concentrating on their clinical import.

Cervical intervertebral disc space narrowing and size of intervertebral foramina

Computer-assisted simulation of C4-C5, C5-C6, and C6-C7 intervertebral disc space narrowing was performed on 16 anatomic specimen cervical spines to determine the relationship of the cross sectional foraminal areas with the degree of narrowing of the cervical intervertebral disc space. Compared with normal foraminal area values, reduction of 20% to 30% of the foraminal area was found after 1 mm narrowing of the intervertebral disc spaces; reduction of 30% to 40% of the foraminal area was found after 2 mm narrowing of the intervertebral disc space; and reduction of 35% to 45% of the foraminal area was found after 3 mm narrowing of the intervertebral disc space. Statistically significant differences were found among the remaining cross sectional foraminal areas after different degrees of intervertebral disc space narrowing. Compression of the nerve root within the intervertebral foramina after the collapse of the intervertebral disc space cannot be ignored, and an appropriate surgical procedure to maintain the normal height of the disc space is essential. The size of the intervertebral foramen is related directly to the height of the intervertebral disc space. A 3-mm vertical reduction of the intervertebral disc space is associated more frequently with severe narrowing of the neuroforamen.

A review of biomechanics of the central nervous system--Part I: spinal canal deformations resulting from changes in posture

OBJECTIVE

To discuss how the spinal cord deforms as a result of changes in posture or biomechanical alterations of the spine.

DATA COLLECTION

A hand search of available reference texts and a computer search of literature from the Index Medicus sources were collected, with special emphasis placed on spinal canal changes caused by various postural rotations and translations of the skull, thorax, and pelvis.

RESULTS

All spinal postures will deform the spinal canal. Flexion causes a small increase in canal diameter and volume as the vertebral lamina are separated. Extension causes a small decrease in canal diameter and volume as the vertebral lamina are approximated. Lateral bending and axial rotation cause insignificant changes in spinal canal diameter and volume in cases without stenosis.

CONCLUSIONS

Rotations of the global postural components, head, thoracic cage, and pelvis cause changes in the diameter of the spinal canal and intervertebral foramen. These changes are generally a reduction of less than 1.5 mm in extension, compared with a small increase in flexion of approximately 1 mm. These small changes do not account for the clinical observation of patients having increased neurologic signs and symptoms in flexion.

Anatomic considerations of C2 nerve root ganglion

STUDY DESIGN

Dissection and observation of the dorsal root ganglion of the second cervical spinal nerve bilaterally.

OBJECTIVES

To determine the position of the C2 dorsal root ganglion and the heights of the C2 ganglion and its corresponding foramen.

SUMMARY OF BACKGROUND DATA

The dorsal root ganglion has been well studied in the middle and lower cervical spine and in the lumbar spine. In no previous study are the position and height of the C2 dorsal root ganglion and its corresponding foramen described.

METHODS

Fifteen cadaveric cervical spines were exposed posteriorly. The C2 nerve roots and ganglia were dissected between the arch of the atlas and the lamina of the axis. The heights of the C2 ganglion and foramen were measured. The location of the C2 ganglion was also macroscopically observed.

RESULTS

The heights of the C2 ganglion and foramen are 5.7 +/- 0.8 mm and 7.7 +/- 1.2 mm, respectively. The C2 ganglion occupies 76% of the foramen height. All C2 dorsal root ganglia are confined within foramens between the arch of the atlas and the lamina of the axis.

CONCLUSIONS

The C2 dorsal dorsal root ganglia are all proximally placed and occupy most of the foramen height, which may render the C2 ganglion vulnerable to entrapment.