Pathogenesis of cervical spondylotic myelopathy

Surgical management of tic-induced myelopathy and the importance of perioperative tic control: illustrative cases

BACKGROUND

Degenerative cervical myelopathy (DCM) is the most common cause of adult spinal cord dysfunction. Tourette syndrome (TS) represents a rare cause of DCM that is incompletely characterized in the literature. Patients with TS might develop repetitive involuntary cervical movements that can accelerate spondylotic changes. Therefore, patients with myelopathy secondary to TS or other tic disorders might exhibit DCM symptoms at younger ages. The present study examines the surgical management of DCM secondary to TS in the literature and describes the outcomes of 3 patients who were treated for DCM secondary to TS.

OBSERVATIONS

In these 3 described cases, fractures led to DCM in 2 patients, while cervical spondylosis led to DCM in 1 patient, all associated with TS. Treating motor tics with medications or deep brain stimulation (DBS) provided effective tic management. All 3 patients experienced improvements in their neurological symptoms following surgery, consistent with other reports in the literature.

LESSONS

When treating patients with cervical myelopathy secondary to TS, the authors recommend prioritizing motor tic management prior to considering secondary interventions such as surgery. According to the authors, treating motor tics with medications or DBS provides effective tic management. This approach allows for an uncomplicated postoperative course and satisfactory relief of cervical myelopathy. https://thejns.org/doi/10.3171/CASE24751.

Correlation Between Pre-Operative Diffusion Tensor Imaging Indices and Post-Operative Outcome in Degenerative Cervical Myelopathy: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review.

OBJECTIVES

The correlation between pre-operative diffusion tensor imaging (DTI) metrics and post-operative clinical outcomes in patients with degenerative cervical myelopathy (DCM) has been widely investigated with different studies reporting varied findings. We conducted a systematic review to determine the association between DTI metric and clinical outcomes after surgery.

METHODS

We identified relevant articles that investigated the relationship between pre-operative DTI indices and post-operative outcome in DCM patients by searching PubMed/MEDLINE, Web of Science, Scopus, and EMBASE from inception until October 2023. In addition, quantitative synthesis and meta-analyses were performed.

RESULTS

FA was significantly correlated with postoperative JOA or mJOA across all age and follow up subgroups, changes observed in JOA or mJOA from preoperative to postoperative stages (Δ JOA or Δ mJOA) in subgroups aged 65 and above and in those with a follow-up period of 6 months or more, as well as recovery rate in all studies pooled together and also in the under-65 age bracket. Additionally, a significant correlation was demonstrated between recovery rate and ADC across all age groups. No other significant correlations were discovered between DTI parameters (MD, AD, and ADC) and post-operative outcomes.

CONCLUSION

DTI is a quantitative noninvasive evaluation tool that correlates with severity of DCM. However, the current evidence is still elusive regarding whether DTI metric is a validated tool for predicting the degree of post-operative recovery, which could potentially be useful in patient selection for surgery.

Progressive spinal cord compression technique in experimental rabbit animal model for cervical spondylotic myelopathy

INTRODUCTION

Cervical spondylotic myelopathy (CSM) presently estimated at 54% population, commonly cause of myelopathy due to chronic compression of the spinal cord in older people. Physiological injuries caused by static and dynamic forces including compressed, pinched, and pulled out inducing secondary injuries at the molecular level.

METHODS

We examined the rabbit model approach with the clinical case of spondylotic myelopathy, in which the disk and facet maintained the cervical spine mobility, and compression was given 0.5 mm per week three times in this model. In this study, a group of 14 days was made (early into the chronic phase) and the 21 day group had a chronic process for 1 week, that period can be categorized as a chronic process and CSM is a chronic process. By examining motor scores, histological examination and immunohistochemistry of the spinal cord, this model efficiently produces myelopathy. The distribution of microglia expressing GFAP, S100-β, and Neurofilaments were observed by immunohistochemical techniques.

RESULTS

There was a significant difference in the number of cells expressing GFAP between the control group and the 21-day compression group (p = 0.001). There is a decrease in S100-β expression of spinal cord tissue after receiving compression exposure. There was a significant difference in the number of cells expressing NF between the control group, the 14-day compression group (p = 0.04) and 21-day compression group (p = 0.04).

DISCUSSION

Neurons have the intrinsic ability to regenerate after injury, although not spontaneously. Cervical spondylotic myelopathy causes permanent neurological disorders, partly due to glial scar formation consisting of astrocytes and microglia. The difference between our study and previous research methods is that we perform compression of the spinal cord in stages (0.5 mm, 1.0 mm & 1.5 mm) so that it is more like the natural occurrence of chronic spinal cord compression.

CONCLUSION

An increasing of GFAP value in this study indicates the presence of astrocyte activity which can be associated with chronic spinal cord injury. There is a decrease in S100-β expression of spinal cord tissue neuron cells after receiving compression exposure. The expression of NF decreased indicating degenerative axons.

Degenerative Cervical Myelopathy: Insights into Its Pathobiology and Molecular Mechanisms

Degenerative cervical myelopathy (DCM), earlier referred to as cervical spondylotic myelopathy (CSM), is the most common and serious neurological disorder in the elderly population caused by chronic progressive compression or irritation of the spinal cord in the neck. The clinical features of DCM include localised neck pain and functional impairment of motor function in the arms, fingers and hands. If left untreated, this can lead to significant and permanent nerve damage including paralysis and death. Despite recent advancements in understanding the DCM pathology, prognosis remains poor and little is known about the molecular mechanisms underlying its pathogenesis. Moreover, there is scant evidence for the best treatment suitable for DCM patients. Decompressive surgery remains the most effective long-term treatment for this pathology, although the decision of when to perform such a procedure remains challenging. Given the fact that the aged population in the world is continuously increasing, DCM is posing a formidable challenge that needs urgent attention. Here, in this comprehensive review, we discuss the current knowledge of DCM pathology, including epidemiology, diagnosis, natural history, pathophysiology, risk factors, molecular features and treatment options. In addition to describing different scoring and classification systems used by clinicians in diagnosing DCM, we also highlight how advanced imaging techniques are being used to study the disease process. Last but not the least, we discuss several molecular underpinnings of DCM aetiology, including the cells involved and the pathways and molecules that are hallmarks of this disease.

Reliability and validity of multi-shot DWI in diagnosis of cervical spondylotic myelopathy: a study based on 3-T MRI

OBJECTIVE

To investigate whether multi-shot diffusion-weighted imaging (ms-DWI) could be applied in diagnosis and quantitative evaluation of cervical spondylotic myelopathy (CSM).

METHODS

Thirty-three normal volunteers and 78 patients with CSM were included in this study. The apparent diffusion coefficient (ADC) values were measured at C2-C7 levels on sagittal section ADC map. The intraclass correlation coefficient (ICC) and Bland and Altman plot and Spearman coefficient were used to quantify the reproducibility of test and retest and inter-rater reliability. Pearson correlations were calculated to compare lADC and rADC versus mJOA and NDI scores. Receiver operating characteristic curve and the area under the curve (AUC) were applied to evaluate the diagnostic reliability.

RESULTS

There was no statistically significant difference between ADC values obtained from normal volunteers at C2-C7 levels (P < 0.05). The ICC and spearman coefficient of lADC and rADC indicated excellent test-retest and inter-rater reliability. The mean lADC and rADC were significantly higher from patients than that from volunteers (all P < 0.01). The lADC had moderate to good correlations with mJOA and NDI (all P < 0.0001). Moreover, rADC had good to excellent correlations with mJOA and NDI (all P < 0.0001). Comparing AUCs, rADC was significantly superior in diagnosis which participants were CSM than lADC (P = 0.0118).

CONCLUSION

The ms-DWI could be applied in diagnosis and quantitive assessment of CSM according to lADC and rADC. A new parameter, rADC, could be served as a diagnostic indice for CSM, which may quantitively reflect the severity of CSM. These slides can be retrieved under Electronic Supplementary Material.

MR diffusion tensor imaging of the spinal cord: can it help in early detection of cervical spondylotic myelopathy and assessment of its severity?

Background

The aim of this study is to evaluate the potential application of MR diffusion tensor imaging (with calculation of fractional anisotropy (FA) values) in assessment of the spondylotic cervical spinal canal compromise and comparison with the information issued from conventional MR sequences for early detection of cervical spondylotic myelopathy (CSM). Thirty patients (11 males and 19 females) were included in this study; age ranged from 22 to 70 years (mean age = 44). All patients had conventional and diffusion tensor imaging (DTI) examinations of the cervical spine for detection and assessment of degree of cervical cord myelopathy. FA values of the whole cord circumference and at 3, 6, 9, 12 o’clock positions of the normal cord (opposite to C2), opposite to the most affected disc, and below the level of the most affected disc were measured.

Results

High statistically significant P values were obtained when comparing the FA values of the normal cord with the cord opposite to the most affected disc, the normal cord with the cord below the affected disc and the cord at the level of the most affected disc with the cord below the level of the most affected disc.

Conclusions

DTI of the cervical spinal cord with FA measurement in patients with cervical spondylosis helps in early detection of cervical cord compressive myelopathy prior to appearance of changes in conventional MRI, which can improve the clinical outcome and help in treatment plans.

Patterns of Neurological Recovery After Anterior Decompression With Fusion and Posterior Decompression With Laminoplasty for the Treatment of Multilevel Cervical Spondylotic Myelopathy

STUDY DESIGN

The pattern of neurological recovery in the overall modified Japanese Orthopedic Association scores, upper limb function score, and lower limb function score after surgical decompression for patients suffering from multilevel cervical spondylotic myelopathy (CSM) were analyzed in this independent retrospective study.

OBJECTIVE

The primary objective of this retrospective study was to compare the upper and lower limb function changes after anterior decompression with fusion versus posterior decompression with laminoplasty for patients suffering from multilevel CSM. An additional objective was to describe the neural recovery speed.

SUMMARY OF BACKGROUND DATA

Few comparative studies have been conducted to evaluate the outcome of anterior versus posterior surgery in multilevel CSM. However, these assessments tend to be of a more global perspective, looking at a composite score for upper limb, lower limb, and bladder function. No reports have separately analyzed the upper and lower limb function changes after anterior and posterior decompression for multilevel CSM.

MATERIALS AND METHODS

A total of 132 patients were classified into anterior and posterior decompression groups based on the different surgical approach they underwent. The pattern of neurological recovery in the overall modified Japanese Orthopedic Association scores, upper limb function score, and lower limb function score after surgical decompression were documented and analyzed.

RESULTS

There was no significant difference in the overall neurological recovery between anterior and posterior decompression groups. But in terms of the upper or lower limb function changes after operation, it appeared that the upper limbs recovered better with anterior decompression. The surgical approach did not significantly alter lower extremity recovery potential. In addition, most of the neurological recovery occurred in the first 9 months after surgical decompression.

CONCLUSIONS

We recommend a individualized approach when it is difficult to determine an anterior or posterior surgery for multilevel CSM. Rehabilitation training should be carried out as early as possible.

Regression of Disc-Osteophyte Complexes Following Laminoplasty Versus Laminectomy with Fusion for Cervical Spondylotic Myelopathy

BACKGROUND

Laminectomy with fusion (LF) and laminoplasty are two posterior-based surgical approaches for the surgical treatment of cervical spondylotic myelopathy (CSM). The decompressive effect of these approaches is thought to be primarily related to the dorsal drift of the spinal cord away from ventral compressive structures. A lesser known mechanism of spinal cord decompression following cervical LF is regression of the ventral disc osteophyte complexes which is postulated to result from the alteration of motion across the fused motion segment. The goal of this study was to determine whether regression of the ventral disc-osteophyte complexes occur following laminoplasty and compare the magnitude of this occurrence to cervical laminectomy and fusion.

METHODS

Seventy patients with CSM who underwent pre- and postoperative magnetic resonance imaging (MRI) and were treated with either laminoplasty or LF. The size of the disc-osteophyte complex at all operative levels were measured on pre- and postoperative MRI using digital calipers.

RESULTS

The laminoplasty group consisted of 25 patients with an average age of 54.9 and a mean of 3.24 surgical levels while the LF group consisted of 45 patients with an average age of 65.4 and a mean of 3.44 surgical levels (age, p < 0.0001; levels, p= 0.46). The average time interval between pre- and post-operative MRI was 16.2 and 15.6 months in the laminoplasty and LF groups, respectively (p = 0.91). The average time interval between surgery and post-operative MRI was 10.1 and 10.7 months in the laminoplasty and LF groups, respectively (p = 0.86). When comparing pre- and post-operative MRI, there was a 9.59% decrease in disc-osteophyte complex size from 3.84mm ± 0.74 to 3.47mm ± 0.86 in the laminoplasty group compared to a 35.4% decrease in disc-osteophyte complex size from 4.60mm ± 1.06 to 2.98mm ± 1.33 in LF group (laminoplasty, p < 0.0001; LF, p = 0.0067). Using logistic regression analysis, LF, increased time interval between surgery and post-operative MRI, high cobb angle, and straight sagittal alignment were all independently associated with increased disc-osteophyte complex regression (p < 0.05). No differences in functional outcomes (as defined by mJOA scores) was found between the two surgical techniques.

CONCLUSIONS

In patients with CSM that had a posterior surgical approach, LF is associated with a larger interval regression in disc-osteophyte complex size compared to laminoplasty. This is likely related to the loss of motion of the cervical spine after surgery as governed by Wolff's law and the Heuter-Volkmann's principle. Although the decompressive effect of LF and laminoplasty is primarily related to the dorsal drift of the spinal cord away from ventral compressive structures, disc-osteophyte complex regression likely provides another mechanism of spinal cord decompression.

Utility of the clivo-axial angle in assessing brainstem deformity: pilot study and literature review

There is growing recognition of the kyphotic clivo-axial angle (CXA) as an index of risk of brainstem deformity and craniocervical instability. This review of literature and prospective pilot study is the first to address the potential correlation between correction of the pathological CXA and postoperative clinical outcome. The CXA is a useful sentinel to alert the radiologist and surgeon to the possibility of brainstem deformity or instability. Ten adult subjects with ventral brainstem compression, radiographically manifest as a kyphotic CXA, underwent correction of deformity (normalization of the CXA) prior to fusion and occipito-cervical stabilization. The subjects were assessed preoperatively and at one, three, six, and twelve months after surgery, using established clinical metrics: the visual analog pain scale (VAS), American Spinal InjuryAssociation Impairment Scale (ASIA), Oswestry Neck Disability Index, SF 36, and Karnofsky Index. Parametric and non-parametric statistical tests were performed to correlate clinical outcome with CXA. No major complications were observed. Two patients showed pedicle screws adjacent to but not deforming the vertebral artery on post-operative CT scan. All clinical metrics showed statistically significant improvement. Mean CXA was normalized from 135.8° to 163.7°. Correction of abnormal CXA correlated with statistically significant clinical improvement in this cohort of patients. The study supports the thesis that the CXA maybe an important metric for predicting the risk of brainstem and upper spinal cord deformation. Further study is feasible and warranted.

Addressing Stretch Myelopathy in Multilevel Cervical Kyphosis with Posterior Surgery Using Cervical Pedicle Screws

Study Design

Technique description and retrospective data analysis.

Purpose

To describe the technique of cervical kyphosis correction with partial facetectomies and evaluate the outcome of single-stage posterior decompression and kyphosis correction in multilevel cervical myelopathy.

Overview of Literature

Kyphosis correction in multilevel cervical myelopathy involves anterior and posterior surgery. With the advent of cervical pedicle screw-rod instrumentation, single-stage posterior kyphosis correction is feasible and can address stretch myelopathy by posterior shortening.

Methods

Nine patients underwent single-stage posterior decompression and kyphosis correction for multilevel cervical myelopathy using cervical pedicle screw instrumentation from March 2011 to February 2014 and were evaluated preoperatively and postoperatively with modified Japanese Orthopaedic Association (mJOA) scoring and computed tomography scans for radiological measurements. Kyphosis assessment was made with Ishihara curvature index and C2–C7 Cobb's angle. The linear length of the spinal canal and the actual spinal canal length were also evaluated. The average follow-up was 40.56 months (range, 20 to 53 months).

Results

The average preoperative C2–7 Cobb's angle of 6.3° (1° to 12°) improved to 2° (10° to −9°). Ishihara index improved from −15.8% (−30.5% to −4.7%) to −3.66% (−14.5% to +12.6%). The actual spinal canal length decreased from 83.64 mm (range, 76.8 to 91.82 mm) to 82.68 mm (range, 75.85 to 90.78 mm). The preoperative mJOA score of 7.8 (range, 3 to 11) improved to 15.0 (range, 13 to 17).

Conclusions

Single-stage posterior decompression and kyphosis correction using cervical pedicle screws for multilevel cervical myelopathy may address stretch myelopathy, in addition to decompression in the transverse plane. However, cervical lordosis was not achieved with this method as predictably as by the anterior approach. The present study shows evidence of mild shortening of cervical spinal canal and a positive correlation between canal shortening and clinical improvement.

Kinematic relationship between missed ligamentum flavum bulge and degenerative factors in the cervical spine

BACKGROUND CONTEXT

Bulging of ligamentum flavum can happen with the aging process and can lead to compression of the spinal cord and nerves. However, the distribution and the risk factors associated with a missed ligamentum flavum bulge (LFB) are unknown.

PURPOSE

The aim was to evaluate the distribution and risk factors associated with missed LFB in the cervical spine.

STUDY DESIGN

This was a retrospective analysis of kinematic magnetic resonance images (kMRI).

PATIENT SAMPLE

Patients diagnosed with symptomatic neck pain or radiculopathy between March 2011 and October 2012 were included.

OUTCOME MEASURES

The outcome measures were missed LFB and degenerative factors.

METHODS

A total of 200 patients (1,000 cervical segments) underwent upright kMRI in neutral, flexion, and extension postures. The LFB, sagittal cervical angles, disc herniation, disc degeneration, disc height, angular motion, translational motion, age, and gender were recorded. After excluding segments with LFB in neutral and flexion position, Pearson and Spearman correlation coefficients were used to evaluate the relation between the risk factors and missed LFB in the extension position.

RESULTS

The average depth of LFB was 0.24±0.71 mm at C2-C3, 1.02±1.42 mm at C3-C4, 1.65±1.48 mm at C4-C5, 2.13±1.37 mm at C5-C6, and 1.05±1.54 mm at C6-C7. The distribution of LFB was the most frequent at C5-C6 level (76.58%) followed by C4-C5 (63.06%). Disc herniation, disc degeneration, angular variation, and translational motion were significantly correlated with missed LFB at C4-C5 andC5-C6. Disc degeneration was the only factor significantly correlated with missed LFB at all cervical segments.

CONCLUSIONS

Occurrence and depth of missed LFB was the highest at C4-C5 and C5-C6 compared with other cervical levels. Disc degeneration, disc herniation, angular variation, and translational motion could play a role in the development of LFB at C4-C5 andC5-C6.

Three-dimensional alteration of cervical anterior spinal artery and anterior radicular artery in rat model of chronic spinal cord compression by micro-CT

OBJECTIVE

To investigate the spatial and temporal changes of anterior spinal artery (ASA) and anterior radicular artery (ARA) of chronic compressive spinal cord injury on rat model by three-dimensional micro-CT.

METHODS

48 rats were divided into two groups: sham control group (n=24) and compressive spinal cord injury group (n=24). A C6 semi-laminectomy was performed in the sham control group, while a water-absorbable polyurethane polymer was implanted into C6 epidural space in the compression group. The Basso Beattie Bresnahan (BBB) score and somatosensory evoked potentials (SEP) were used to evaluate neurological function. Micro-CT scanning was used to investigate the change of ASA and ARA after perfusion at the 1th (n=6), 28th (n=6), 42th (n=6) and 70th (n=6) day of post operation. The diameter, angle-off and vascular index (VI) was measured by 3D micro-CT.

RESULTS

In comparison with sham control, BBB score have a significant reduction at the 28th day (p<0.05) and abnormal SEP have a significant severity at the 28th day (p<0.05). Both of them have a significant improvement at the 70th day compared with that of the 28th day (p<0.05). VI shows the amount of microvessels reduced at the 28th day (p<0.05) and increased at the 70th day (p<0.05). The diameter and angle-off of ASA and ARA also changed significantly at the 28th, 42th, 70th day (p<0.05).

CONCLUSION

There was a significant alteration of cervical anterior spinal artery and anterior radicular artery after chronic cervical spinal cord compression. Alteration of ASA and ARA may affect the vascular density of spinal cord and play an important role in neural functional change of chronic cervical spinal cord compression through 3D micro-CT.

Tract-Specific Diffusion Tensor Imaging in Cervical Spondylotic Myelopathy Before and After Decompressive Spinal Surgery: Preliminary Results

PURPOSE

Diffusion tensor imaging (DTI) metrics of the cervical spinal cord in patients with cervical spondylotic myelopathy (CSM) were compared to those measured in healthy volunteers, using tract-specific region of interests (ROIs) across all cervical intervertebral disc levels.

METHODS

Magnetic resonance (MR) imaging of the cervical spinal cord was performed in four patients with CSM and in five healthy volunteers on a 3-T MR scanner. Region-specific fractional anisotropy (FA) and mean diffusivity (MD) were calculated on axial imaging with ROI placement in the anterior, lateral, and posterior regions of the spinal cord. FA and MD were also calculated on sagittal acquisitions. Nonparametric statistical tests were used to compare controls and patients before and after surgery.

RESULTS

FA values were significantly lower (p = 0.050) and MD values were significantly higher (p = 0.014) in CSM patients measured at level of maximal compression before surgery than in healthy controls in lateral and posterior ROIs, respectively. In posterior ROIs, MD values were significantly higher in patients before surgery compared to controls at all levels except C7-T1.

CONCLUSION

Patients with CSM may demonstrate region-specific changes in DTI metrics when compared to healthy controls. Changes in DTI metrics may also occur at levels remote from site of compression.

Cervical duraplasty with tenting sutures via laminoplasty for cervical flexion myelopathy in patients with Hirayama disease: successful decompression of a “tight dural canal in flexion” without spinal fusion

Object

Hirayama disease, juvenile muscular atrophy of the distal upper extremity, is a rare type of cervical flexion segmental myelopathy and its etiology is still being debated. Two theories have been proposed: a “contact pressure” theory and “tight dural canal in flexion” theory. Previously reported treatments, including conservative neck collar therapy and surgical spinal fusion, used fixation of the cervical spine with the aim of avoiding contact pressure between the cord and anterior structures. On the other hand, treatment by duraplasty without spinal fusion has also been used, which aims at decompressing a tight dural canal in flexion by preventing abnormal forward displacement of the posterior dura mater without restricting cervical motion in young patients.

The authors developed a new surgical approach for treating a tight dural canal in flexion in patients with Hirayama disease: cervical duraplasty with tenting sutures via laminoplasty without spinal fusion. With this treatment they aimed to both decompress the spinal cord and preserve as much cervical motion as possible. The purpose of this study was to assess the clinical outcomes of patients who underwent this new surgical procedure and to investigate the etiology of Hirayama disease.

Methods

Six male patients (age range 17–23 years) with Hirayama disease underwent surgery between 2006 and 2012. The pre- and postoperative anteroposterior diameters of the dural canal in the flexed neck position, grip strength of the bilateral upper extremities, cervical alignment (C2–7), and cervical local flexion range of motion were compared. The presence or absence of surgical complications was assessed. To investigate the comparison group of Hirayama disease treated with spinal decompression, the PubMed database was searched for all relevant Englishlanguage case reports and series published between 1990 and 2013.

Results

The postoperative anteroposterior diameters of the dural canal were significantly expanded in the flexed neck position (7.2 ± 2.2 mm preoperatively vs 9.8 ± 1.7 mm postoperatively, p = 0.001). Grip strength of the upper extremities significantly improved bilaterally (20 ± 14 kg preoperatively vs 26 ± 15 kg postoperatively, p = 0.001). No significant difference was observed between pre- and postoperative cervical alignment in the neutral neck position (7.7° ± 8.1° preoperatively vs 9.0° ± 7.7° postoperatively, p = 0.74) or the cervical local flexion angle in the flexed neck position at the corresponding level of laminoplasty (16.6° ± 5.1° preoperatively vs 15.0° ± 9.4° postoperatively, p = 0.8). No surgical complications were noted, except for transient CSF leakage, which was resolved after lumbar drainage. The systematic review identified 37 cases from 7 reports: 26 with spinal fusion only, 5 with duraplasty without fusion, and 6 with combined duraplasty and fusion. In the largest series, in which 12 cases were treated with anterior fusion, cervical alignment was maintained, but local flexion motion was significantly decreased as a result of fixation. Although significant improvements in or stabilization of grip strength occurred in all 7 reported studies regardless of decompression procedures, one major delayed surgical complication was noted in a patient treated with anterior fusion. The patient developed severe kyphotic changes, which required reconstruction surgeries.

Conclusions

Cervical duraplasty with tenting sutures via laminoplasty prevented abnormal forward displacement of the posterior dura mater while preserving normal anterior structures and flexion motion of the cervical spine without major surgical complications. The clinical improvements achieved by the authors' method support evidence that a tight dural canal in flexion largely contributes to segmental myelopathy in patients with Hirayama disease.

Pediatric iatrogenic thoracic kyphosis and tension myelopathy treated with a thoracic pedicle subtraction osteotomy: a case report and review of the literature

PURPOSE

Pediatric kyphotic deformity is an uncommon clinical entity that can occur following posterior spinal operations and has significant complexity in its treatment. Tension myelopathy in a pediatric patient with a thoracic kyphotic deformity has not been reported in the literature.

CASE REPORT

We present a 17-year-old boy with a progressive thoracic kyphosis and tension myelopathy 4 years after he underwent a thoracic laminoplasty at an outside institution for the treatment of a dorsal spinal arachnoid cyst. At our institution, he was treated with a pedicle subtraction osteotomy as well as thoracic Ponte osteotomies for sagittal plane correction to relieve the tension myelopathy.

CONCLUSIONS

Both clinical and radiographic improvements were observed after surgery. We review the literature on pediatric thoracic kyphosis and tension myelopathy and the treatment of these pathologies.

Spinal stenosis

Narrowing of the spinal canal or foramina is a common finding in spine imaging of the elderly. Only when symptoms of neurogenic claudication and/or cervical myelopathy are present is a spinal stenosis diagnosis made, either of the lumbar spine, cervical spine or both (only very rarely is the thoracic spine involved). Epidemiological data suggest an incidence of 1 case per 100 000 for cervical spine stenosis and 5 cases per 100 000 for lumbar spine stenosis. Cervical myelopathy in patients over 50 years of age is most commonly due to cervical spine stenosis. Symptomatic spinal narrowing can be congenital, or, more frequently, acquired. The latter may be the result of systemic illneses, namely endocrinopathies (such as Cushing disease or acromegaly), calcium metabolism disorders (including hyporarthyroidism and Paget disease), inflammatory diseases (such as rheumathoid arthritis) and infectious diseases. Physical examination is more often abnormal in cervical spondylotic myeloptahy whereas in lumbar spinal stenosis it is typically normal. Therefore spinal stenosis diagnosis relies on the clinical picture corresponding to conspicuous causative changes identified by imaging techniques, most importantly CT and MRI. Other ancillary diagnostic tests are more likely to be yielding for establishing a differential diagnosis, namely vascular claudication. Most patients have a progressive presentation and are offered non operative management as first treatment strategy. Surgery is indicated for progressive intolerable symptoms or, more rarely, for the neurologically catastrophic initial presentations. Surgical strategy consists mainly of decompression (depending on the anatomical level and type of narrowing: laminectomy, foraminotomy, discectomy, corporectomy) with additional instrumentation should spinal stability and sagittal balance be at risk. For cervical spine stenosis the main objective of surgery is to halt disease progression. There is class 1b evidence that surgery is of benefit for lumbar stenosis at least in the short term.

A summary of assessment tools for patients suffering from cervical spondylotic myelopathy: a systematic review on validity, reliability and responsiveness

PURPOSE

One of the objectives of this review is to summarize the important features of a good scale. A second aim is to conduct a systematic review to identify scales that can detect the presence of cervical myelopathy and to determine their psychometric properties including validity, reliability and responsiveness.

METHODS

A thorough literature search was performed using MEDLINE, MEDLINE in process, EMBASE, and Cochrane Central Register of Controlled Trials. Articles were included in this study if they compared scale measurements between a control and a myelopathic patient population or if they discussed any psychometric property of a scale.

RESULTS

An ideal scale should be one that is quantifiable, valid, sensitive, responsive and easy to perform, has high inter/intra-rater reliability, internal consistency and a suitable distribution, and is one-dimensional and relevant. In the context of cervical spondylotic myelopathy, it is essential that the scale also addresses the pathophysiology, its key signs and symptoms as well as its natural history. For the systematic review, the search yielded 5,745 citations. Of these, 37 met inclusion criteria, 10 explored the ability of a scale to detect myelopathy, 23 examined validity by assessing correlation between scales, 10 reported reliability, 8 analyzed responsiveness, and 6 discussed internal consistency. The most frequently reported scale was short form-36 (n = 16) followed by Nurick grade (n = 14), Japanese Orthopaedic Association (n = 13), (modified) Japanese Orthopaedic Association (n = 7) and grip and release test (n = 6). Four studies each presented results on the Cooper, Harsh and 30-m walking test.

CONCLUSION

This review summarizes outcome measures used to assess the presence and severity of cervical myelopathy. It includes several validation studies as well as those that have reported the responsiveness and reliability of various measures.

Cervical spondylotic myelopathy with vitamin B12 deficiency: Two case reports

Although it has been observed that a vitamin B₁₂ (VB₁₂) deficiency may lead to defects in the nervous system, there is a lack of studies elucidating whether VB₁₂ has a role in the pathogenesis of cervical spondylotic myelopathy (CSM). The present study describes two cases of CSM observed in the clinic, where the patients presented with common characteristics of the typical clinical symptoms; however, T2-weighted magnetic resonance imaging examinations revealed that although the degree of spinal cord compression was not serious, the spinal cord exhibited significant high signal changes. At the same time, the serum VB₁₂ levels of the two patients were lower compared with those of normal controls. The symptoms of the patients improved following anterior cervical decompression surgery and VB₁₂ replacement therapy. The incidence of CSM in the two patients may have been correlated with a lack of VB₁₂. Therefore, it is recommended that the serum VB₁₂ levels are checked in cases of CSM where the standard imaging and clinical manifestations do not fully match.

Diffusion tensor imaging correlates with the clinical assessment of disease severity in cervical spondylotic myelopathy and predicts outcome following surgery

BACKGROUND AND PURPOSE

CSM is a common neurologic disease that results in progressive disability and eventual paralysis without appropriate treatment. Imaging plays a significant role in the evaluation of CSM and has evolved with recent technical advances. We sought to systematically explore the relationship between clinical disease severity and DTI in CSM, and to investigate the potential use of DTI in surgical decision-making models.

MATERIALS AND METHODS

MR imaging studies and clinical assessments were prospectively collected on 30 patients with CSM. Spearman correlations were used to investigate associations between clinical disease severity and FA at the time of diagnosis. Clinical assessment was performed using mJOA, Nurick, Short Form-36, and NDI scores. Fifteen patients with CSM subsequently underwent decompressive surgery; Spearman correlation and logistic regression were applied to this cohort to study the relationship between baseline DTI measurements and postoperative outcome. Conventional imaging (spinal cord T2 signal intensity and degree of stenosis) was evaluated for comparison with DTI.

RESULTS

At diagnosis, FA demonstrated a strong correlation with baseline mJOA (r = 0.62, P < .01) and Nurick (r = -0.46, P = .01) scores. After surgery, recovery of function demonstrated by improvement in NDI score was associated with higher FA values on preoperative DTI (r = -0.61, P = .04). Severely affected patients with CSM with disproportionately high FA tended to achieve greater mJOA scores after surgery compared with subjects with lower FA (P = .08). T2 signal intensity was associated with functional status at baseline but did not predict postoperative outcome; degree of stenosis lacked any significant correlation with clinical parameters.

CONCLUSIONS

DTI may be a useful diagnostic tool for assessing disease severity in CSM. The predictive value of DTI regarding postoperative outcome may improve surgical decision-making and facilitate health care outcomes research.

The denticulate ligament: anatomical properties, functional and clinical significance

BACKGROUND

It is widely believed that the main function of denticulate ligaments (DLs) is to stabilize the spinal cord within the vertebral canal. The aim of this study was to assess the anatomical and histological structure of the DLs and to document any regional differences.

METHODS

Five formalin-fixed adult cadavers were used. The DLs were exposed via the posterior approach, and detailed anatomy and histology of these structures were documented.

RESULTS

The main findings were: (1) each DL is composed of a single narrow fibrous strip that extends from the craniovertebral junction to T12, and each also features 18-20 triangular extensions that attach to the dura at their apices; (2) the triangular extensions are smaller and more numerous at the cervical levels, and are larger and less numerous at the thoracic levels; (3) the apices of the extensions attach to the dura via fibrous bands at cervical levels (each band 3-5 mm long) and lower thoracic levels (21-26 mm long), whereas they attach directly to the dura at upper thoracic levels; (4) the narrow fibrous strip of the DL features longitudinally oriented collagen fibers, whereas the triangular extensions are composed of transverse and obliquely oriented collagen fibers. The collagen fibers are thicker and more abundant at the cervical than at the thoracic levels.

CONCLUSION

DL histology and anatomy are strongly correlated with the function of this structure at different spinal levels. It is important to have accurate knowledge about DLs as these structures are relevant for clinical procedures that involve the spinal cord or craniovertebral junction.

Diffusion tensor imaging in the assessment of ossification of the posterior longitudinal ligament: a report on preliminary results in 3 cases and review of the literature

Cervical spondylotic myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is a common neurosurgical disease that carries high morbidity. OPLL and other degenerative processes cause narrowing of the central canal, with subsequent spinal cord injury. Repeated minor trauma and vascular aberrations have been purported to underlie cervical spondylotic myelopathy, although the exact pathophysiological mechanism is unclear. Regardless, detection of early axonal damage may allow more timely surgical intervention and prediction of functional outcome. Diffusion tensor (DT) imaging of the cervical spine is a novel technique with improved sensitivity compared with conventional anatomical MR imaging that is currently available on most clinical scanners. This review describes the theoretical basis, application, and analysis of DT imaging as it pertains to neurosurgery. Particular emphasis is placed on OPLL.

Spinal cheiro-oral syndrome: a common neurological entity in an unusual site

BACKGROUND AND PURPOSE

Cheiro-oral syndrome (COS) is an established neurological entity characterized by a sensory impairment confined to the mouth angle and ipsilateral finger(s)/ hand. The current understanding of localization is a concomitant involvement of the spinothalamic and trigeminothalamic tract between the cortex and pons. The cervical spinal cord has not been mentioned in this situation yet, and this unusual location may heretofore increase the risk of misdiagnosis.

MATERIAL AND METHODS

Six patients who presented with unilateral COS due to cervical cord disorder are reported.

RESULTS

All patients were women and their age ranged between 42 and 70 years. Their neurological deficits included unilateral paraesthesiae restricted to cheirooral distribution, positive radicular sign, and mild change of tendon reflex. Cervical spinal stenosis at middle/lower cervical spine with variable magnitude of cord compression and intrinsic cord damage was found. A diagnostic dilemma obviously arises from the lack of tangible neurological signs or typical pattern of myelopathy, in addition to the previous concept of cerebral involvement. A benign course ensued in all reported patients.

CONCLUSIONS

Cheiro-oral syndrome can be an early neurological sign for cervical cord disorder; it further suggests that it is a strong neurological but weak localizing sign. A reciprocal influence of multiple factors is considered to generate COS at the cervical cord. Therefore, an absence of brain pathology should lead to a thorough examination of the cervical cord in case of COS.

Anatomy and biomechanics of the spinal column and cord

The field of biomechanics combines the disciplines of biology and engineering, attempting to quantitatively describe the complicated properties of biological materials. These properties depend not only upon the inherent attributes of its constituents but also upon how the constituents are arranged relative to each other. Its importance in understanding spinal column and spinal cord pathology cannot be overemphasized. This chapter is a primer on the application of biomechanical principles to the normal and pathological spine. The basic concepts of biomechanics will first be reviewed followed by a review of the structural anatomy of the osteoligamentous spinal column and the biomechanics of injury. Relevant spinal cord anatomy will then be addressed as well as current biomechanical theories of spinal cord injury.

Cessation of cyclic vomiting in a 7-year-old girl after upper cervical chiropractic care: a case report

OBJECTIVE

The purpose of this case report is to describe chiropractic management of a child with cyclic vomiting syndrome.

CLINICAL FEATURES

A 7-year-old girl had a history of cyclic vomiting episodes for the past 4 1/2 years. She also had a 2-month history of headaches and stomachache.

INTERVENTION AND OUTCOME

The patient received low-force chiropractic spinal manipulation to her upper cervical spine. There was improvement in her symptoms within an hour after the chiropractic manipulation. Her symptoms only returned after direct trauma to her neck. The recurring symptoms again disappeared immediately after treatment.

CONCLUSION

This case study suggests that there may be a role for the use of chiropractic spinal manipulative therapy for treating cyclic vomiting syndrome. Controlled studies are necessary to aid our understanding of this finding.

Deformative stress associated with an abnormal clivo-axial angle: A finite element analysis

Background:

Chiari malformation, functional cranial settling and subtle forms of basilar invagination result in biomechanical neuraxial stress, manifested by bulbar symptoms, myelopathy and headache or neck pain. Finite element analysis is a means of predicting stress due to load, deformity and strain. The authors postulate linkage between finite element analysis (FEA)-predicted biomechanical neuraxial stress and metrics of neurological function.

Methods:

A prospective, Internal Review Board (IRB)-approved study examined a cohort of 5 children with Chiari I malformation or basilar invagination. Standardized outcome metrics were used. Patients underwent suboccipital decompression where indicated, open reduction of the abnormal clivo-axial angle or basilar invagination to correct ventral brainstem deformity, and stabilization/ fusion. FEA predictions of neuraxial preoperative and postoperative stress were correlated with clinical metrics.

Results:

Mean follow-up was 32 months (range, 7-64). There were no operative complications. Paired t tests/ Wilcoxon signed-rank tests comparing preoperative and postoperative status were statistically significant for pain, bulbar symptoms, quality of life, function but not sensorimotor status. Clinical improvement paralleled reduction in predicted biomechanical neuraxial stress within the corticospinal tract, dorsal columns and nucleus solitarius.

Conclusion:

The results are concurrent with others, that normalization of the clivo-axial angle, fusion-stabilization is associated with clinical improvement. FEA computations are consistent with the notion that reduction of deformative stress results in clinical improvement. This pilot study supports further investigation in the relationship between biomechanical stress and central nervous system (CNS) function.

Three-dimensional finite element model of the cervical spinal cord: preliminary results of injury mechanism analysis

STUDY DESIGN

A three-dimensional finite element investigation.

OBJECTIVES

To create a three-dimensional finite element model of the cervical spinal cord enlargement and to simulate a hyperextension injury of the cervical cord.

SUMMARY OF BACKGROUND DATA

Experimental studies are difficult to simulate the complex mechanism of spinal cord injuries. The introduction of three-dimensional modeling technique into neurotrauma studies is essential to further understand mechanical behavior of the nerve tissue during traumatic injuries.

METHODS

Geometrical reconstruction of cervical spinal cord enlargement was developed based on the morphologic features of each segment of the fresh human cervical cord. After the validation of the model, the pinching condition in the hyperextension injuries was simulated with compressive and extension forces applied on the cervical enlargement model. The average von Mises stress of the 9 anatomic regions, such as anterior funiculus, lateral part of the lateral funiculus, medial part of the lateral funiculus, lateral part of the posterior funiculus, medial part of the posterior funiculus, anterior horn, the bottom of anterior horn, the apex of posterior horn, the cervix cornu posterioris, and caput cornu posterioris was recorded.

RESULTS

The force-displacement response of the spinal cord under compression and axial tension loading was close to the experimental results reported in the literature. The stress distribution of the spinal cord according to the numerical simulation and the morphologic features of the in vivo experiment were also in close agreement. Hyperextension injury simulation showed high localized stress at the anterior and posterior horn in the gray matter.

CONCLUSION

The finite element method as a three-dimensional modeling technique can improve the understanding of the biomechanical behavior of the spinal cord. The results of hyperextension injury simulation of the cervical spinal cord probably account for the predominance of the hand weakness in patients with central cord injury.

Cerebrospinal fluid stasis and its clinical significance

We hypothesize that stasis of the cerebrospinal fluid (CSF) occurs commonly and is detrimental to health. Physiologic factors affecting the normal circulation of CSF include cardiovascular, respiratory, and vasomotor influences. The CSF maintains the electrolytic environment of the central nervous system (CNS), influences systemic acid-base balance, serves as a medium for the supply of nutrients to neuronal and glial cells, functions as a lymphatic system for the CNS by removing the waste products of cellular metabolism, and transports hormones, neurotransmitters, releasing factors, and other neuropeptides throughout the CNS. Physiologic impedance or cessation of CSF flow may occur commonly in the absence of degenerative changes or pathology and may compromise the normal physiologic functions of the CSF. CSF appears to be particularly prone to stasis within the spinal canal. CSF stasis may be associated with adverse mechanical cord tension, vertebral subluxation syndrome, reduced cranial rhythmic impulse, and restricted respiratory function. Increased sympathetic tone, facilitated spinal segments, dural tension, and decreased CSF flow have been described as closely related aspects of an overall pattern of structural and energetic dysfunction in the axial skeleton and CNS. Therapies directed at affecting CSF flow include osteopathic care (especially cranial manipulation), craniosacral therapy, chiropractic adjustment of the spine and cranium, Network Care (formerly Network Chiropractic), massage therapy (including lymphatic drainage techniques), yoga, therapeutic breath-work, and cerebrospinal fluid technique. Further investigation into the nature and causation of CSF stasis, its potential effects upon human health, and effective therapies for its correction is warranted.

Dynamic Canal Encroachment of Ligamentum Flavum

OBJECTIVE

In extension of the cervical spine, the ligamentum flavum (LF) may bulge and intrude into the vertebral canal and cause symptoms of myelopathy and/or radiculopathy in patients with canal stenosis. Knowledge of the relationship between the extension angle and the physiologic changes of the LF is important for a better understanding of the clinical symptoms. The current study was designed to demonstrate the dynamic correlativity of canal intrusion of the LF bulge with the extension angle of the cervical spine.

METHODS

With a novel method, the probe of the electrical resistance strain gauge was put into the cervical canals of 14 cadaveric specimens. The LF bulge distance of six segments (C2-C3 to C7-T1) and corresponding extension angles of every 5 degrees from 0 degrees to 45 degrees were collected. Angle-bulge curves were drawn.

RESULTS

In overextension (45 degrees ), C5-C6 had the biggest canal intrusion depth (3.478+/-0.527 mm), whereas the upper and lower segments declined gradually (C5-C6>C4-C5>C6-C7>C3-C4>C7-T1>C2-C3). The curves in all segments were sigmoidal, which demonstrated the dynamic change of LF, that is, during the process of extension, LF shortened and contracted first, after the original length was reached, it began to bulge and burst into the canal.

CONCLUSION

The current study has provided a method to measure inner canal kinematic changes in intact spinal specimens.

The Amelioration of Symptoms in Cervical Spinal Stenosis with Spinal Cord Deformation Through Specific Chiropractic Manipulation: A Case Report with Long-Term Follow-Up

OBJECTIVE

To describe the chiropractic management of a patient with paresthesia on the entire left side of her body and magnetic resonance imaging (MRI)-documented cervical spinal cord deformation secondary to cervical spinal stenosis.

CLINICAL FEATURES

A 70-year-old special education teacher had neck pain, headaches, and burning paresthesia on the entire left side of her body. These symptoms developed within hours of being injured in a side-impact motor vehicle accident. Prior to her visit, she had been misdiagnosed with a cerebrovascular accident.

INTERVENTION AND OUTCOMES

Additional diagnostic studies revealed that the patient was suffering from cervical spinal stenosis with spinal cord deformation. Two manipulative technique systems (Advanced Biostructural Therapy and Atlas Coccygeal Technique) unique to the chiropractic profession and based on the theory of relief of adverse mechanical neural tension were administered to the patient. This intervention provided complete relief of the patient's complaints. The patient remained symptom-free at long-term follow-up, 1 year postaccident.

CONCLUSION

There is a paucity of published reports describing the treatment of cervical spinal stenosis through manipulative methods. Existing reports of the manipulative management of cervical spondylosis suggest that traditional manual therapy is ineffective or even contraindicated. This case reports the excellent short-term and long-term response of a 70-year-old patient with MRI-documented cervical spinal stenosis and spinal cord deformation to less traditional, uniquely chiropractic manipulative techniques. This appears to be the first case (reported in the indexed literature) that describes the successful amelioration of the symptoms of cervical spinal stenosis through chiropractic manipulation. More research into the less traditional chiropractic systems of spinal manipulation should be undertaken.

The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis

Syringomyelia is frequently accompanied by an extramedullary lesion at the foramen magnum, particularly a Chiari I malformation. Although syringomyelia associated with foramen magnum obstruction has characteristic clinical, radiological, and neuropathological features, its pathogenesis remains unclear. Currently prevalent hydrodynamical theories assert that obstruction of the subarachnoid space at the foramen magnum interferes with flow of cerebrospinal fluid (CSF) between the spinal and the intracranial subarachnoid compartments. As a result, spinal CSF is driven into the spinal cord through the perivascular spaces to form a syrinx. These theories are implausible biophysically because none postulates a pump adequate to drive fluid through these spaces. None of the theories can explain why syrinx pressure is higher than CSF pressure; why extensive gliosis, edema, and vascular wall thickening regularly occur; and why the composition of syrinx fluid is not identical with that of CSF. A new theory of pathogenesis is proposed to address these difficulties. In the presence of subarachnoid obstruction at the foramen magnum, a variety of activities, such as assuming the erect posture, coughing or straining, and pulsatile fluctuations of CSF pressure during the cardiac cycle, produce transiently higher CSF pressure above the block than below it. There are corresponding changes in transmural venous and capillary pressure favoring dilation of vessels below the block and collapse of vessels above the block. The spatially uneven change of vessel caliber produces mechanical stress on the spinal cord, particularly caudal to the block. The mechanical stress, coupled with venous and capillary dilation, partially disrupt the blood-spinal cord barrier, allowing ultrafiltration of crystalloids and accumulation of a protein-poor fluid. The proposed theory is consistent with the neuropathological findings in syringomyelia and with the pressure and composition of syrinx fluid. It also accounts for the prolonged course of syringomyelia and its aggravation by cough, strain, and assumption of an erect posture. It contributes to understanding the low incidence and the morphology of syringobulbia. It explains the poorly understood presentation of foramen magnum meningiomas with symptoms of a mid- to low-cervical myelopathy. The theory also affords an understanding of the late recurrence of symptoms in children with hydromyelia who are treated with a ventricular shunt.

Mechanism of the spinal cord injury and the cervical spondylotic myelopathy: new approach based on the mechanical features of the spinal cord white and gray matter

OBJECT

The authors have previously investigated the mechanical properties of the white and gray matter in the bovine cervical spinal cord, demonstrating that the gray matter is more rigid, although more fragile, than the white matter. In the present study they conducted additional tensile tests on the bovine cervical spinal cord by changing strain levels and strain rates applied to the white and gray matter.

METHODS

Based on their testing, the authors found the following: 1) Stress within the spinal cord relaxes over time. 2) Intracord stress is related to the strain rates or levels. The finite element method was used to compute the stress distribution within the spinal cord under three compressive loading conditions. Results from the computations showed a different stress distribution in the white and gray matter, where the distribution of stress varied with strain rate, compression volume, and the position of compression.

CONCLUSIONS

These differences in mechanical properties between the white and gray matter constitute different mechanisms contributing to the development of tissue damage and clinical symptoms.

Anterior decompression for cervical spondylotic myelopathy

Cervical spondylotic myelopathy is a clinical entity that manifests itself due to compression and ischemia of the spinal cord. The goal of treatment is to decompress the spinal cord and stabilize the spine in neutral, anatomical position. Since the obstruction and compression of the cord are localized in front of the cord, it is obvious that an anterior surgical approach is the preferred one. The different surgical procedures, complications, and outcome are discussed here.

Neck and low back pain

These cases represent a sample of conditions that impact the spine and paraspinous structures. Central to establishing a correct diagnosis and the cost-effective application of neurodiagnostic tests is a careful history and physical examination. The primary care physician is often the only physician to have a perception of the whole patient. The primary care physician is in an excellent position to initiate the evaluation of patients with spine symptoms and, where appropriate, monitor the treatment plans of consulting physicians.

Comparison of spinal cord gray matter and white matter softness: measurement by pipette aspiration method

OBJECT

Although the gray matter of the spinal cord has been thought to be softer than the white matter, there is no evidence to support this belief. Because the spinal cord is extremely soft, it has been difficult to measure the mechanical properties of the gray and white matter. The modulis of elasticity of the gray and white matter were measured in situ by using a pipette aspiration method.

METHOD

The spinal cord specimens were excised from Japanese white rabbits. Specimens were cut to display the surfaces of axial, frontal, and sagittal sections. The surfaces of the gray and white matter were aspirated using a 0.8-mm-inner-diameter glass pipette while monitoring with a video microscope, and the deformed length in the pipette was measured on a monitor. In each case the modulus of elasticity was calculated by comparing the relationship between the aspiration pressure and aspirated volume of the specimen with that determined by finite element analysis. The moduli of elasticity of the gray and white matter were 3.4+/-1.4 kPa (mean +/- standard deviation) and 3.4+/-0.9 kPa in the axial section, 3+/-0.3 kPa and 3.5+/-0.5 kPa in the frontal section, and 3.5+/-0.9 kPa and 2.8+/-0.4 kPa in the sagittal section, respectively.

CONCLUSIONS

No significant difference in modulus of elasticity was shown between the gray and white matter of the spinal in sections made in various directions.

Gray matter of the bovine cervical spinal cord is mechanically more rigid and fragile than the white matter

The gray matter of the cervical spinal cord has been thought to be equally or less rigid than the white matter. Based on this assumption, various studies have been conducted on the changes of stress distributions within the spinal cord under mechanical compression, although the mechanical properties of the white and gray matters had not been fully elucidated. The present study measured the mechanical properties of the white and gray matter of bovine spinal cords. For both the white and gray matter, the stress-strain curves had a nonlinear region, followed by a linear region, and then a region where the stresses plateaued before failure. In the nonlinear region, stress was not significantly different between the gray and white matter samples (strain approximately 0-10%), while stress and Young's modulus in the gray matter was significantly higher than the white matter in the linear part of the curve. The gray matter ruptured at lower strains than the white matter. These findings demonstrated the gray matter is more rigid and fragile than the white matter, and the conventional assumption (i.e., the white matter is more rigid than the gray matter) is not correct. We then applied our data to computer simulations using the finite element method, and confirmed that simulations agreed with actual magnetic resonance imaging findings of the spinal cord under compression. In future computer simulations, including finite element method using our data, changes in stress and strain within the cervical spinal cord under compression would be clarified in more detail, and our findings would also help to elucidate the area which can easily receive histologic damage or which could have hemodynamic disorders under mechanical compression, as well as severity and location of biochemical and molecular biological changes.

Ventricular size in pseudotumor cerebri and the theory of impaired CSF absorption

The purpose of this theoretical study is to determine whether the absence of ventricular enlargement in pseudotumor cerebri (PTC) is consistent with the theory that PTC is caused by reduced absorption of cerebrospinal fluid (CSF), either from increased outflow resistance at the arachnoid villi or from obstruction of the dural venous sinuses. We model the brain as a thick spherical shell of parenchyma, enclosing a CSF-filled ventricular system, and surrounded by a thin cerebral subarachnoid space (CSAS). We treat the parenchyma as a porous solid matrix, filled with interstitial fluid and blood vessels. We subject the model to a uniform increase in CSF pressure (CSFP) and solve the equations of poroelasticity for the resulting displacements of parenchymal tissue. The effect of a rise in CSFP on ventricular size depends on the response of the cerebral blood vessels and the degree to which the pia is tethered to the dura. If the cerebral vessels decrease in caliber with increasing CSFP, a rise in CSFP causes the ventricles to contract and the CSAS to expand if the pial surface is free to move inward, but causes slight ventricular enlargement if the pia is tethered to the dura. If, instead, the vessels dilate, the ventricles contract and the CSAS becomes effaced. Small, normal, or slightly enlarged ventricles in PTC are consistent with the theory of reduced CSF absorption.

Spinal cord MRI hyperintensities in cervical spondylosis: an ischemic pathogenesis?

The pathophysiology of focal spinal cord MRI T2 hyperintensity (SCHI) in patients with cervical spondylosis is uncertain. This study was undertaken to determine the frequency and cause of SCHI. The authors reviewed serial cervical spine magnetic resonance imaging (MRI) reports and reviewed scans with spondylosis and cord compression or SCHI. The authors noted the location, shape, and extent of SCHI, and severity of spondylosis (expressed as a spondylosis score [SS]). The authors recorded the age and vascular risk factors for each patient. Nineteen of 273 scans (7%) with cervical spondylosis and 19 of 36 scans (53%) with cord compression had SCHI. The SCHI extended for one vertebral level from the compression in 12 patients and for three vertebral levels in 5 patients, and were distant from the compression in 2 patients. The SCHI had a focal, symmetrical, anterior spinal artery terminal zone location in 16 of 19 scans (84%). A rim isointense with normal cord separated all SCHI from the pial surface. Patients with SCHI were older (58.3 years +/- 12.8 years versus 46.8 +/- 8.1 years) (p = 0.007) and had a higher SS (5.7 +/- 2.4 versus 3.9 +/- 1.4) (p = 0.02) than patients without SCHI. The SCHI relates to the severity of cervical spondylosis. The anterior spinal artery territory location, the normal cord between SCHI and the compressive lesion, and the presence of SCHI at a distance from the compressive level all suggest an ischemic basis for SCHI.