Toshiki Kawamoto

Delayed myelopathy induced by chronic compression in the rat spinal cord

Cervical myelopathy is a common cause of neurological disability among the elderly; however, the exact mechanism for the insidious and progressive deterioration remains to be elucidated. To study the pathophysiology, we developed a simple experimental model reproducing the course. In rats, a thin sheet of expanding polymer was implanted microsurgically underneath the C5‐C6 laminae. In the control group, the polymer sheet was removed immediately. Changes in motor functions were monitored for 25 weeks after the operation, with voluntary exercise activity measured by odometer attached to revolving cages, and forced running capability measured by duration of exercise on a rotating treadmill. Motor neurons were counted stereologically in continuous sections. In the compression group, the forced running capability deteriorated after a latent period of 17 weeks and progressively thereafter. In the control group, it stayed unchanged throughout 25 weeks. Course of the voluntary exercise was comparable between the groups. Motor neuron density in the compression group decreased significantly in 9 weeks (−20.3%) and 25 weeks (−35.5%), but not in 1 or 3 weeks. This practical model properly reproduces characteristic features of the clinical cervical myelopathy, with progressive motor disturbance after a latency and insidious neuronal loss preceding the symptoms. Ann Neurol 2004

Proper management of the rotational vertebral artery occlusion secondary to spondylosis

A 66-year-old man with cervical spondylosis noticed severe vertigo when turning his head to the right. He underwent subclavian arteriography elsewhere, which showed a block of the contrast medium in the right vertebral artery (VA) at the C5/6 level when the patient turned his head to the right. After referral to our institute, however, postcontrast CT scan revealed an attenuated shadow of the venous plexus around the right VA at the C3/4 level. Repeated selective angiography with rotation of the head after visualization of the entire VA verified the level of obstruction to be at C3/4. Resection of the C4 transverse process through an anterior approach with drilling of the C3/4 spondylotic spur of the uncinate processi completely resolved the arterial impingement and the symptom. When evaluating rotational VA occlusion, dynamic angiography with selective catheterization is essential in determining which level is affected. The postcontrast CT scan is also useful because it suggests the level even without head rotation.

False-Positive and False-Negative Results of Motor Evoked Potential Monitoring During Surgery for Intramedullary Spinal Cord Tumors

BACKGROUND Motor evoked potential (MEP) recording is used as a method to monitor integrity of the motor system during surgery for intramedullary tumors (IMTs). Reliable sensitivity of the monitoring in predicting functional deterioration has been reported. However, we observed false positives and false negatives in our experience of 250 surgeries of IMTs. OBJECTIVE To delineate specificity and sensitivity of MEP monitoring and to elucidate its limitations and usefulness. METHODS From 2008 to 2011, 58 patients underwent 62 surgeries for IMTs. MEP monitoring was performed in 59 operations using transcranial electrical stimulation. Correlation with changes in muscle strength and locomotion was analyzed. A group undergoing clipping for unruptured aneurysms was compared for elicitation of MEP. RESULTS Of 212 muscles monitored in the 59 operations, MEP was recorded in 150 (71%). Positive MEP warnings, defined as amplitude decrease below 20% of the initial level, occurred in 37 muscles, but 22 of these (59%) did not have postoperative weakness (false positive). Positive predictive value was limited to 0.41. Of 113 muscles with no MEP warnings, 8 muscles developed postoperative weakness (false negative, 7%). Negative predictive value was 0.93. MEP responses were not elicited in 58 muscles (27%). By contrast, during clipping for unruptured aneurysms, MEP was recorded in 216 of 222 muscles (96%). CONCLUSION MEP monitoring has a limitation in predicting postoperative weakness in surgery for IMTs. False-positive and false-negative indices were abundant, with sensitivity and specificity of 0.65 and 0.83 in predicting postoperative weakness.

Multidetector Spinal CT Angiography with Intraarterial Contrast Injection As a Scout Survey for Spinal Vascular Lesions

Shinji Yamamoto, M. D., Ryu Kurokawa, M. D., Kazushige Itoki, M. D., Tetsuro Shingo, M. D., Toshiki Kawamoto, M. D., Phyo Kim, M. D. 獨協医科大学脳神経外科/〒321-0293 下都賀郡壬生町北小林 880[連絡先:山本慎司] Address reprint requests to:Shinji Yamamoto, M. D., Department of Neurosurgery, Dokkyo University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi 321-0293, Japan 動注 MDCT angiography による脊髄血管病変の補助診断 Multidetector Spinal CT Angiography with Intraarterial Contrast Injection As a Scout Survey for Spinal Vascular