A case of Isaacs syndrome with high CSF protein and a large cisterna magna

An 11-year-old boy exhibited continuous muscle fiber activity. He had suffered from stiffness of his hands, difficulty in relaxing his hands after gripping, and making skilled movements with his fingers. His clinical symptoms improved after treatment with carbamazepine. Electromyography (EMG) showed that he had continuous electrical discharges both at rest and during sleep. These discharges completely disappeared after the peripheral nerve was blocked with Lidocaine. An evoked electromyogram showed suppression of abnormal discharges after the F response. These electrophysiological findings indicated that the disorder originated in the spinal anterior horn cells. CT scanning showed a large cisterna magna in the posterior cranial fossa. Protein in the cerebrospinal fluid was elevated.