Abstract
The cause of the cervical spondylotic amyotrophy (CSA) is thought to be the nerve root damage, the impairment of the anterior horn of spinal cord, or the mixed type of both lesions. In CSA patients, measured were the compound muscle action potentials (CMAP), central motor conduction time (CMCT) and F wave. CMAP stimulated at supramaximal Erb point were recorded from the proximal (deltoid and biceps) and distal muscles (extensor digitorum and abductor digiti minimi). The aim of this study was to determine the clinical usefulness of these electrophysiological tests for the pathophysiological analyses and the prediction of prognosis of CSA patients. Fourteen patients with proximal type CSA and 3 with distal type CSA were examined. CMAP were recorded from the above muscles, while CMCT was calculated from the motor evoked potentials (MEP) and F wave. All of the atrophied muscles showed decreased CMAP amplitude. Not only the affected muscles but also the healthy muscles as well as proximal muscles in distal type CSA patients showed the decreased amplitude. CMAP ratio to the reference value was correlated with manual muscle testing (MMT). Interestingly there found patients with full MMT score whose CMAP amplitudes were decreased. Even in the patients with full MMT, CMAP evoked by Erb point stimulation was able to detect the preclinical abnormalities, and the decrease in CMAP from the several spinal cord segments suggests that wide range of the segments was affected. The delayed CMCT and the F wave abnormalities were found in 36% of proximal type CSA patients and all distal type CSA patients. Furthermore, the patients with postoperative poor prognosis were the cases that myelopathy across a wide range was suggested by preoperative CMCT and F wave abnormalities. Thus, these electrophysiological tests on CSA patients can be useful both in the evaluation of the affected regions and the prediction of the postoperative prognosis.
