A Case of Isaacs' Syndrome

ABSTRACT

A case of Isaacs syndrome with Trousseau s phenomenon wac studied electrophysiologically and histologically. The needle electromyography showed typical neuromyotonic discharges of spontaneous recurrent high-frequency(150-300Hz) bursts of motor unit activity with 0.5-3 second of duration and typical waning pattern This discharge was not suppressed by brachial plexus block Motor and sensory nerve conduction velocities were either s!ightly below or in the lower range of normal. In repetitive nerve stimulation test a decremental response to low rate stimulation was noted in abductor digiti quinti muscle. On sural nerve biopsy, there was a decrease in the number of myelinated nerve fibers showing both axonal and myelin degeneration The clinical and electrophysiologic abnormalities improved considerably after treatment with phenytoin.