Prediction of Surgical Outcome for Proximal-Type Cervical Spondylotic Amyotrophy Novel Mode of Assessment Using Compound Action Potentials of Deltoid and Biceps Brachii and Central Motor Conduction Time

Abstract

Case studies of patients with cervical spondylotic amyotrophy used compound muscle action potentials (CMAPs) of deltoid and biceps brachii muscles and central motor conduction time (CMCT). To discuss surgical outcome for proximal-type cervical spondylotic amyotrophy in the context of results obtained with CMAPs and CMCT. There have been no reports that correlate surgical outcome with CMAPs of deltoid and biceps brachii muscles or with CMCT. A retrospective study was performed for 24 patients with proximal-type cervical spondylotic amyotrophy who underwent surgical treatment of the cervical spine. Erb-point-stimulated CMAPs were recorded in the deltoid and biceps. The percent amplitude of CMAPs was calculated in comparison with the opposite side. Motor-evoked potentials were recorded from bilateral abductor digiti minimi. CMAPs and F waves were recorded after supramaximal electric stimulation of ulnar nerves. CMCT was calculated as follows: motor-evoked potentials latency - (CMAPs' latency + F latency - 1)/2 (ms). Muscle strength was evaluated using manual muscle testing. Improvements in strength were classified as excellent, good, or fair. The improvement was graded as excellent in 12 cases, good in 2 cases, and fair in 10 cases. The average percentage for CMAPs' amplitude on the affected side compared with the normal side in deltoid and biceps brachii muscles was significantly different between the excellent and fair patient groups. The CMCT on the affected side was not significantly different between excellent and fair patient groups. The average percentage range of deltoid and biceps brachii muscle CMAPs' amplitude determined at the onset of illness correlated significantly with postoperative recovery. Surgical intervention of the cervical spine should be performed in patients in whom the average percentage of CMAPs' amplitude in deltoid and biceps brachii muscles ranges from 30% to 50%.