CT myelography with intramedullary enhancement in cervical spondylosis

Decoding unusual MR findings: Spinal cord edema in atypical cervical spondylotic myelopathy-A case report and literature review

We report a case of a young man with a slow progression of cervical spondylotic myelopathy (CSM). Cervical magnetic resonance imaging (MRI) revealed a mild cervical discbulging at C5-C6 and an area of atypically enlarged intramedullary high signal intensity extending from C4-C7 (T2-weighted) with contrast enhancement at C5-C6 (T1-weighted). Neurological and radiological diagnoses tend to favor demyelinating diseases, which interfere with the diagnosis of CSM. Patients were followed up and examined by MRI at 3 months, 1 year, and 2 years after surgery. The patient's symptoms improved immediately postoperatively. The functional result according to the modified Japanese Orthopedic Association (JOA) score improved from 10 to 13 within 3 months. He continued to improve neurologically over the first postoperative year. Two years postoperatively, a T2-weighted MRI showed that the edema signal had disappeared completely, and a fat-saturated T2-weighted MRI showed only slight abnormal signal. The numbness and weakness of the extremities had improved, and his JOA score was 16. Spinal cord edema is occasionally seen with CSM. In the case presented, the contrast enhancement was localized at the site of the greatest narrowing of the spinal canal and compression of the spinal cord. This coincidence was the best indicator of a mechanical cause of the spinal cord changes. This feature should increase physician's confidence in distinguishing CSM from intramedullary tumors and myelitis. Surgical decompression may be beneficial in improving neurologic outcomes.

Correlation between "Snake-Eyes" Sign and Role of Surgery with a Focus on Postoperative Outcome: A Systematic Review

(1) Background: The "snake-eyes" sign represents a unique finding characterized by bilateral hyperintense symmetric, circular, or ovoid foci on T2-weighted MRI sequences in the anterior horn cells of the spinal cord. There are conflicting opinions as some authors affirm that it does not affect the prognosis of cervical myelopathy while other papers emphasize the opposite, stating how the "snake-eyes" sign constitutes an irreversible lesion and a predictor of poor prognosis. This systematic review evaluates the correlation between the "snake-eyes" sign and the prognosis of cervical myelopathy after surgery including anterior and/or posterior approaches; (2) Methods: A systematic literature review was conducted following the PRISMA statement and a total of seven papers were included; (3) Results: A total of 419 patients were evaluated, with a mean age of 55.72 ± 14.38 years. After surgery, 26.01% of patients experienced a significant clinical improvement, while in 61.81%, there was no significant improvement. In particular, 144 of 196 patients (73.5%) treated through an anterior approach and 114 of 223 (51.1%) that underwent a posterior approach, did not present a significant improvement. Furthermore, in 12.17% of patients, the postoperative outcome was not reported, leading to a high risk of bias in the assessment of the prognostic significance of the "snake-eyes" appearance; (4) Conclusions: The "snake-eyes" sign is usually considered as an unfavorable predictive marker for myelopathic surgical patients, but the pathophysiology is still unclear, and the results have not yet reached unified levels of evidence.

Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis

The exact pathogenesis of syringomyelia associated with Chiari type 1 malformation is unknown, although a number of authors have reported their theories of syrinx formation. The purpose of this review is to understand evidences based on the known theories and to create a new hypothesis of the pathogenesis. We critically review the literatures on clinicopathological, radiological, and clinical features of this disorder. The previously proposed theories mainly focused on the driven mechanisms of the cerebrospinal fluid (CSF) into the spinal cord. They did not fully explain radiological features or effects of surgical treatment such as shunting procedures. Common findings of the syrinx in clinicopathological studies were the communication with the central canal and extracanalicular extension to the posterior gray matter. Most of the magnetic resonance imaging studies demonstrated blockade and alternated CSF dynamics at the foramen magnum, but failed to show direct communication of the syrinx with the CSF spaces. Pressure studies revealed almost identical intrasyrinx pressure to the subarachnoid space and decreased compliance of the spinal CSF space. Recent imaging studies suggest that the extracellular fluid accumulation may play an important role. The review of evidences promotes a new hypothesis of syrinx formation. Decreased absorption mechanisms of the extracellular fluid may underlie the pathogenesis of syringomyelia. Reduced compliance of the posterior spinal veins associated with the decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and formation of syringomyelia.

Predictors of Outcome of Surgery for Cervical Compressive Myelopathy: Retrospective Analysis and Prospective Study

The outcomes of surgical treatment in 80 patients with cervical compressive myelopathy were retrospectively reviewed to examined the correlations between surgical outcomes and the following seven predictive factors: age at surgery, duration of symptoms, severity of myelopathy, number of compressed segments, intramedullary high intensity segments on T(2)-weighted magnetic resonance (MR) imaging, surgical method, and the type of disease. The recovery rates were evaluated at 3 months after the surgery. Significant correlations were observed between recovery rate and duration of symptoms, severity of myelopathy, and high intensity segments on T(2)-weighted MR imaging. No statistical correlation was observed with the other factors. Multivariate analysis revealed significant correlations between recovery rate and duration of symptoms and number of high intensity segments on T(2)-weighted MR imaging. The multiple regression equation was expressed as follows: recovery rate = 82.981 + 0.101 x (age) - 0.675 x (duration) - 1.452 x (number of compressed segments) - 1.451 x (preoperative Neurosurgical Cervical Spine Scale) - 13.826 x (number of high intensity segments). Based on this predicted formula, we compared the predicted and actual recovery rates for 17 patients treated recently. The two values were similar except in two patients with long duration of symptoms. We conclude that the surgical outcome can be predicted to a certain extent and this information could be provided to patients considering surgery for cervical compressive myelopathy.

Cervical Spondylotic Amyotrophy Treated by Anterior Decompression-Three Case Reports-

Cervical spondylotic amyotrophy (CSA) is a rare type of cervical spondylotic disorder. The surgical treatment of CSA is controversial. We treated three patients with the proximal type of CSA by anterior decompression. Three men (65, 61, and 58 years old) presented with CSA manifesting as unilateral muscle weakness and atrophy in the deltoid and biceps muscles without significant sensory deficit. Preoperative neuroradiological examinations revealed anterolateral spinal cord compression in one patient and ventral root compression in two patients at the C4-5 and C5-6 spaces. Magnetic resonance (MR) imaging showed no abnormal intramedullary signal intensity in any patient. Vertebrotomy deviated to the lesion side was performed to provide a better view of the laterally situated osteophytes. Anterior decompression was focused on the paramedial to lateral area, and further foraminotomy was performed according to the radiological findings. After decompression, intervertebral instrumentation was performed using titanium cervical cages. Two of the patients had good recovery of motor strength and one had moderate recovery despite persistent motor atrophy. Surgical intervention is effective in patients with CSA despite severe muscle atrophy unless MR imaging shows the presence of severe degenerative intramedullary lesion.

Postmortem study of the spinal cord showing snake-eyes appearance due to damage by ossification of the posterior longitudinal ligament and kyphotic deformity

CLINICAL DESIGN: A case report.

OBJECTIVES

To elucidate the clinical role of snake-eyes appearance in this case, correlation between radiological, clinical and postmortem study was performed.

SETTING

Aichi, Japan.

CASE REPORT

A 73-year-old man developed weakness and pain in the upper limbs due to kyphotic deformity secondary to laminectomy for cervical ossification of the posterior longitudinal ligament. Axial magnetic resonance imaging revealed snake-eyes appearance from C4 to C6. He died of acute myocardial infarction 3 months after anterior decompressive surgery.

RESULTS

A postmortem examination of the cervical spinal cord showed small cystic six necrotic areas at the junction of the central gray matter and the ventrolateral posterior column, one in the right and one in the left, in association with neuronal loss in the anterior horn.

CONCLUSIONS

Bilateral small intramedullary high-signal areas known as 'snake-eyes appearance' located around the central gray matter and the ventrolateral posterior column, are associated with neuronal loss in the compressed anterior horn that played an important role in worsening weakness of the upper limbs.

Presymptomatic spondylotic cervical cord compression

STUDY DESIGN

We conducted a cohort study of clinically asymptomatic spondylotic cervical cord compression cases with the primary end point of the development of clinical signs of cervical myelopathy.

OBJECTIVES

To investigate whether various demographic, clinical, radiologic, and electrophysiological parameters could predict progression from clinically asymptomatic (preclinical) spondylotic cervical cord compression to symptomatic myelopathy.

SUMMARY OF BACKGROUND DATA

The data available on the prediction of the outcome in surgical and conservative treatment of spondylotic cervical myelopathy are controversial. Little is known about the clinical natural history of asymptomatic magnetic resonance image-detected spondylotic cervical cord compression and/or changes of signal intensity.

METHODS

A group of 66 patients (32 women, 34 men, median age 50 years) with magnetic resonance signs of spondylotic cervical cord compression but without clear clinical signs of myelopathy was followed prospectively for at least 2 years (range, 2-8 years; median, 4 years). Various demographic, clinical, imaging, and electrophysiological parameters were correlated with clinical outcome.

RESULTS

Clinical signs of myelopathy during the follow-up period were detected in 13 patients (19.7%). The only variables significantly associated with the development of clinically symptomatic spondylotic cervical myelopathy (SCM) were the presence of symptomatic cervical radiculopathy, electromyographic signs of anterior horn lesion, and abnormal somatosensory-evoked potentials. A multivariate logistic regression model based on these variables correctly classified 90% of cases into 2 subgroups: a group with development of symptomatic SCM and that without clinical manifestation of subclinical cervical cord compression.

CONCLUSIONS

Electrophysiological abnormalities together with clinical signs of cervical radiculopathy could predict clinical manifestation of preclinical spondylotic cervical cord compression.

Clinicopathological study of "snake-eye appearance" in compressive myelopathy of the cervical spinal cord

OBJECT

The goal of this study was to elucidate the pathophysiological features and clinical significance of the magnetic resonance imaging-documented small intramedullary high signal intensity known as "snake-eye appearance" (SEA) in cases of compressive myelopathy such as cervical spondylosis or ossification of the posterior longitudinal ligament.

METHODS

One hundred forty-four patients with compression myelopathy who underwent surgery between 1998 and 2000 were selected. Intramedullary high signal intensity was found in 79 cases and was divided into two types, SEA and non-SEA (NSEA). The Japan Orthopaedic Association (JOA) scoring system was used for evaluation of pre- and postoperative neurological status. In nine cases of SEA autopsy was performed and specimens were histologically analyzed. The improvement ratio determined by JOA score was 32.2 +/- 15.1% in SEA, 47.1 +/- 12.1% in NSEA, and 50 +/- 18.3% (p < 0.01) in control cases in which high signal intesity was absent. There were significant differences among SEA, NSEA, and control groups. In a separate group of nine patients who died of unrelated causes, histological examination showed small cystic necrosis in the center of the central gray matter of the ventrolateral posterior column and significant neuronal loss in the flattened anterior horn.

CONCLUSIONS

Snake-eye appearance was found to be a product of cystic necrosis resulting from mechanical compression and venous infarction. Destruction of the gray matter accompanying significant neuronal loss in the anterior horn suggested that SEA is an unfavorable prognostic factor for the recovery of upper-extremity motor weakness.

Spinal cord edema: unusual magnetic resonance imaging findings in cervical spondylosis

OBJECT

Spinal cord edema is a rare radiological finding in chronic degenerative disorders of the spine. Between 1997 and 2001, the authors treated six patients with cervical spondylotic myelopathy in whom postoperative spinal cord edema was demonstrated. The authors describe the radiological and clinical features of this unusual condition.

METHODS

The six patients were all men, and ranged in age from 44 to 72 years. All patients presented with mild quadriparesis and underwent laminoplasty or anterior fusion. Preoperative magnetic resonance (MR) imaging revealed marked spinal cord compression with intramedullary hyperintensity on T2-weighted sequences and spinal cord enhancement at the compression level after administration of Gd. After surgery, spinal cord edema was observed in all patients; the spinal cord appeared swollen on the postoperative MR images. Preoperative and postoperative Gd-enhanced MR imaging demonstrated clear enhancement of the white matter at the compressed segment Neurologically, five of six patients experienced good improvement of symptoms; however, the spinal cord edema as documented on follow-up MR imaging persisted for several months after surgery.

CONCLUSIONS

The radiological characterization of spinal cord edema was based on the reversible white matter lesion most likely caused by disturbed local venous circulation induced by chronic spinal cord compression. Such unusual MR findings in cervical spondylotic myelopathy should be differentiated from intramedullary spinal cord tumors, demyelinating disorders, or inflammatory processes.

Cervical amyotrophy caused by hypertrophy of the posterior longitudinal ligament

STUDY DESIGN

A case report.

OBJECTIVES

To report a case of cervical amyotrophy caused by hypertrophy of the posterior longitudinal ligament (HPLL).

SETTING

Department of Neurological Surgery, Aichi Medical University, Aichi, Japan.

METHODS

The patient had severe muscular atrophy in the deltoid and triceps with slight localized hypesthesia in the C5 area and severely unstable gait due to diminished vibration sense in the knees and ankles. Magnetic resonance imaging (MRI) showed expanded cord compression from C4 to C6 with intramedullary high-signal intensity due to HPLL. Transverse image MRI was useful to identify the HPLL.

RESULTS

Resection of HPLL was achieved by an anterior approach. Histological findings of the surgical specimens showed thickening of the ligamentous tissue with proliferation of chondrocytes.

CONCLUSIONS

HPLL should be included as a causative pathology of cervical spondylotic amyotrophy. Careful neurological examination including sensory examination of the lower limbs should be performed to avoid confusion with motor neuron disease.

A correlation between magnetic resonance imaging and electrophysiological findings in cervical spondylotic myelopathy

STUDY DESIGN

Correlation between compressed spinal cords on magnetic resonance imaging (MRI) and electrophysiological findings in cervical spondylotic myelopathy patients.

OBJECTIVE

To clarify the correlation between spinal-cord-evoked potentials and MRI measurements of compressed spinal cords in patients with cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

Compression of the spinal cord does not always cause clinical symptoms and it is difficult to infer the degree of dysfunction of the spinal cord from MRI findings.

METHODS

Seventeen patients with cervical spondylotic myelopathy were examined with MRI and spinal-cord-evoked potentials before surgery. Using abnormality in spinal-cord-evoked potentials as indicators of spinal cord morphology, spinal-cord transverse area and compression ratios (central and 1/4-lateral) were measured on T1-weighted axial imaging. The correlations between these dimensions and electrophysiological findings were investigated.

RESULTS

The mean preoperative transverse area of the spinal cord was 47.13 mm2. The mean preoperative central compression ratio of the spinal cord was 34.4%. The mean preoperative 1/4-lateral compression ratio of the spinal cord was 27.5%. A correlation (Spearman r=0.65, P < 0.01) was observed between the 1/4-lateral compression ratio of the spinal cord and the amplitude ratio of spinal-cord-evoked potentials after electric stimulation of the brain (Br(E)-SCEPs).

CONCLUSIONS

The preoperative 1/4-lateral compression ratio of the spinal cord was found to reflect the degree of dysfunction of the corticospinal tracts.

Cervical spondylotic amyotrophy with intramedullary cavity formation

STUDY DESIGN

A case report.

OBJECTIVE

To show that an intramedullary lesion was the cause of cervical spondylotic amyotrophy.

SUMMARY OF BACKGROUND DATA

Cervical spondylotic amyotrophy is the clinical syndrome characterized by muscle wasting and weakness in the upper extremities without a remarkable sensory loss or spastic tetraparesis. It is still unclear whether the ventral roots or the anterior horn are selectively damaged.

METHODS

Magnetic resonance imaging and delayed computed tomographic myelography were performed on a patient who showed severe wasting of the left triceps muscle without any sensory disturbance or long tract sign.

RESULTS

On sagittal magnetic resonance images, a linear area was noted within the spinal cord at C6 and C7 spinal segments, which showed low signal intensity on T1-weighted image and high signal intensity on T2-weighted image. On axial T1-weighted image intramedullary low signal intensity area was observed, which was located in the left anterior horn. On axial T2-weighted image the area showed high signal intensity. A delayed (6 hours) computed tomographic scan after intrathecal injection of metrizamide revealed intramedullary enhancement in the area corresponding to the left anterior horn, which would represent cavitation or cystic necrosis.

CONCLUSIONS

This is the first case report of cervical spondylotic amyotrophy, in which intramedullary lesion was confirmed only at the affected side of the spinal cord.

Can intramedullary signal change on magnetic resonance imaging predict surgical outcome in cervical spondylotic myelopathy?

STUDY DESIGN

A retrospective study evaluating magnetic resonance imaging, computed tomographic myelography, and clinical parameters in patients with cervical spondylotic myelopathy.

OBJECTIVES

To investigate whether magnetic resonance imaging can predict the surgical outcome in patients with cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

No previous studies have established whether areas of high signal intensity in T2-weighted magnetic resonance images can be a predictor of surgical outcomes.

METHODS

Fifty patients with cervical spondylotic myelopathy were examined by magnetic resonance imaging and computed tomographic myelography before surgery and by delayed computed tomographic myelography after surgery. The correlation between the recovery rate and the clinical and imaging parameters was analyzed.

RESULTS

The best prognostic factor was the transverse area of the spinal cord at maximum compression (correlation coefficient, R = 0.58). The presence of high signal intensity areas on T2-weighted magnetic resonance images correlated poorly with the recovery rate (R = -0.29). However, patients with multisegmental areas of high signal intensity on T2-weighted magnetic resonance images tended to have poor surgical results associated with muscle atrophy in the upper extremities. Postoperative delayed computed tomographic myelography showed that multisegmental areas of high signal intensity on T2-weighted magnetic resonance images probably represent cavitation in the central spinal cord.

CONCLUSIONS

Patients with multisegmental areas of high signal intensity on T2-weighted magnetic resonance images tended to have poorer surgical results. However, the transverse area of the spinal cord at the level of maximum compression was a better prognostic indicator.

Magnetic resonance imaging findings in ossification of the posterior longitudinal ligament of the cervical spine

OBJECT

Because of the lack of magnetic resonance (MR) signal from cortical bones, MR imaging is inadequate for diagnosing ossified lesions in the spinal canal. However, MR imaging provides important information on spinal cord morphology and associated soft-tissue abnormality. The purpose of this study is to determine the role of MR imaging in the diagnosis and treatment of patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine.

METHODS

The authors reviewed MR imaging findings in 42 patients with cervical OPLL who were examined with a superconducting MR imaging system. The types of OPLL reviewed included eight cases of continuous, 21 cases of segmental, and 13 cases of the mixed type. All patients were treated surgically either by anterior (26 cases) or posterior decompression (16 cases).

CONCLUSIONS

The T1-weighted images clearly demonstrated the spinal cord deformity caused by OPLL. Associated disc protrusion was found to be present at the maximum compression level in 60% of the patients in this series. The highest incidence of disc protrusion (81%) was found in patients with segmental OPLL. Intramedullary hyperintensity on T2*-weighted imaging was noted in 18 patients (43%). The neurological deficits observed in these 18 patients were significantly more severe than those observed in the other 24 patients. Postoperative MR imaging revealed improvement in the spinal cord deformity, although the intramedullary hyperintensity was still observed in most cases. The present study demonstrates the importance of associated disc protrusion in the development of myelopathy in patients with cervical OPLL. Magnetic resonance imaging findings may be used to help determine the actual levels of spinal cord compression and to suggest the method of surgical treatment.

Cervical spondylotic stenosis and myelopathy: evaluation with computed tomographic myelography

OBJECTIVE

To determine which components of cervical spondylosis are most frequently present in patients with myelopathy.

DESIGN

We reviewed the findings in 93 patients who underwent surgical decompression for cervical spondylotic myelopathy between January 1986 and December 1989 at Mayo Clinic Rochester.

MATERIAL AND METHODS

All 93 patients (72 men and 21 women) underwent computed tomographic (CT) myelography. In addition, magnetic resonance imaging scans were available in 25 patients, and plain CT scans were obtained in 2.

RESULTS

A review of CT myelograms revealed that all neurocompressive intraspinal spondylotic changes were reflected in the shape of the spinal cord. Among the 93 patients with myelopathy, the configuration of the spinal cord could be categorized into primarily three dominant types: A (severe encroachment that compressed the cord into the shape of a banana; N = 40), B (moderate encroachment that produced less prominent compression; N = 23), and C (moderate bilateral uncovertebral spurs; N = 12). As a comparison group, 30 patients with similar spinal cord deformities but without progressive myelopathy were analyzed. Correlation of the two groups showed that myelopathy was present in up to 98% of patients with type A spinal cord, in 75% with type B, and in 71% with type C. The findings on magnetic resonance imaging were similar to those on CT myelography, but the bony spondylotic components were less readily seen.

CONCLUSION

The precise pathophysiologic mechanism of myelopathy in spondylosis remains an enigma. Although the bulk of the data on our patients supports direct compression, we believe that the cause is multifactorial.

Experimental chronic compressive cervical myelopathy

A canine model simulating both cervical spondylosis and its results in delayed progressive myelopathy is presented. This model allowed control of compression, an ongoing assessment of neurological deficits, and evaluation using diagnostic images, frequent electrophysiological tests, local blood flow measurements, and postmortem histological examinations. Subclinical cervical cord compression was achieved in 14 dogs by placing a Teflon washer posteriorly and a Teflon screw anteriorly, producing an average of 29% stenosis of the spinal canal. Four dogs undergoing sham operations were designated as controls. Twelve of the animals undergoing compression developed delayed and progressive clinical signs of myelopathy, with a mean latent period to onset of myelopathy of 7 months. Spinal cord blood flow studies using the hydrogen clearance method showed a significant transient increase in blood flow immediately after compression and a decrease before sacrifice. Somatosensory evoked potential studies indicated progressive deterioration during the period of compression. Magnetic resonance images revealed intramedullary changes. Histological studies showed abnormalities overwhelmingly within the gray matter, including changes in vascular morphology, loss of large motor neurons, necrosis, and cavitation. Axonal degeneration and obvious demyelination were rarely seen. The most profound morphological changes occurred at the site of greatest compression. It is proposed that a momentary arrest of microcirculation occurs during extension of the neck because of loss of the reserve space in the compromised spinal canal. This microcirculatory disturbance is predominant in the watershed area of the cord and mainly affects the highly vulnerable anterior horn cells, leading to neuronal death, necrosis, and eventual cavitation at the junction of the dorsal and anterior horns. Additional supportive evidence of this hypothesis was derived from the literature.

Central spinal cord lesions in stenosis of the cervical canal

34 patients suffering from cervical spondylotic myelopathy confirmed by myelography were examined by delayed CT 6-10 h after myelography. Twelve patients showed bilateral intramedullary collections of contrast medium, predominantly cranial to the stenosis. In these patients males predominated, the duration of clinical symptoms lasted longer although their age was lower. There was no correlation to the degree and the extension of the narrowing of the cervical spinal canal. Half of 20 patients undergoing consecutive decompressive surgery showed intramedullary contrast enhancement, and this was shown again by postoperative MRI in eight. The postoperative clinical and neurophysiological results revealed no change in the majority of patients, but three patients showing intramedullary contrast medium deteriorated in neurophysiological outcome, while only one of the patients in whom intramedullary contrast medium was not noticed got worse.

MRI--the investigation of choice in syringomyelia?

During a 12 month period of operation of a 0.3 Tesla MRI iron cored resistive scanner 74 cases of syringomyelia were diagnosed on clinical, radiological and/or surgical grounds. Without knowledge of any clinical or radiological data the syrinxes were classified into five groups--idiopathic, idiopathic associated with Chiari malformation, tumour associated, post-traumatic and arachnoiditis associated--and the lesion characteristics within each group were compared. Although MRI was extremely sensitive in picking up even small syrinxes, there was considerable overlap of MRI characteristics across the sub-groups, so that two post-traumatic syrinxes had lesion characteristics identifiable with those of tumour syrinx and one intramedullary tumour syrinx had the MRI characteristics of a benign, idiopathic syrinx. It is concluded that meticulous attention to technique, including axial as well as sagittal T1 weighted sequences, and the administration of intravenous paramagnetic contrast media are necessary for detection and accurate classification of syrinxes.

Myelopathic cervical spondylotic lesions demonstrated by magnetic resonance imaging

Eighteen cases are presented in which magnetic resonance (MR) imaging demonstrated two types of lesions in patients with cervical spondylotic myelopathy. In the first type, localized spinal cord changes at the level of compression, consistent with myelomalacia, were revealed best with T2-weighted images as high-intensity spinal cord signals. In the second type, lesions consistent with either cystic necrosis or secondary syrinx were noted locally, and/or extending longitudinally up, and/or down inside the spinal cord. These latter lesions were best revealed as low-intensity signals on T1-weighted MR images and as a signal-void sign (moving fluid) on proton-density or T2-weighted MR images. It is suggested that segmental lesions at the level of the spondylotic bar represent early proton changes from pressure in and around the same zones that evolve into gray-matter enhancement regions shown as "snake-eyes" on delayed computerized tomography (CT) after myelography. The longitudinal lesions are thought to be the same pencil-shaped zones of cystic necrosis evolving into a secondary syrinx in the late stages (and usually found in the anterior portion of the dorsal columns during delayed CT after myelography). As spinal MR imaging continues to improve, these lesions will be demonstrated more clearly within the cord substance.

Syringomyelia after decompressive laminectomy for cervical spondylosis

We describe a case of cervical spondylotic myelopathy in which deterioration occurred a month after decompressive laminectomy. Syringomyelia was then in evidence as seen by myelography and delayed metrizamide computed tomography scanning. The etiology of this finding and its possible relation to the course and treatment of cervical spondylotic myelopathy are discussed.

Cervical flexion myelopathy: a "tight dural canal mechanism". Case report

The authors describe a case of flexion myelopathy due to specific morphological changes of the cervical cord, termed a "tight dural canal mechanism." The patient was an 18-year-old man with progressive weakness and muscle atrophy of the left arm. Neuroradiological examination revealed that the lower cervical cord was compressed during flexion of the cervical spine, but that there was no disc disease or cervical vertebral instability. The cord compression was attributed to a pinching mechanism by the posterior border of the vertebral body and the posterior component of the dura on flexion.