Myasthenia gravis in childhood and infancy. Usefulness of electrophysiologic studies

The diagnostic yield of electrodiagnostic tests was evaluated in 21 children with myasthenia gravis (MG). Twelve children had juvenile autoimmune MG, four had neonatal MG, four had congenital MG, and one had MG with arthrogryposis. Repetitive stimulation (RS) of the ulnar nerve was performed in every patient, sometimes with sensitization by ischemia. When the RS test was negative, the spinal or facial nerve was tested. In the group with neonatal MG, the RS test disclosed a significant decrement in 75% of the patients. Among the 17 other children, the overall percentage of positive RS tests was 88%. An ulnar nerve RS test was positive in 41% of them. Sensitization of ulnar nerve RS by ischemia improved the diagnostic yield to 66%. A spinal or facial nerve RS test was positive in seven of 10 patients. These results confirmed the diagnostic value of RS, with sensitization by ischemia, when necessary, in childhood MG whenever a careful technique is provided.