The usefulness of various diagnostic tests, treatment, and outcome in 27 juvenile myasthenics seen over a 25 year period are reported from the Departments of Pediatrics, Neurology, and Anatomy, University of Iowa. The age of onset in 56% was after 10 years of age. One fourth had ocular myasthenia, one fourth presented with ocular signs and progressed to generalized myasthenia, and half had generalized myasthenia from onset. Ptosis, the most common presenting sign (81%), was unilateral in 33%. In order of descending frequency, the other presenting signs were generalized weakness, dysphagia, diplopia, facial weakness, dysarthria, ophthalmoplegia, and nasal speech. One patient’s mother had MG. The comparative yield of tests showed positive neostigmine and edrophonium tests in 92%, serology was positive for acetylcholine receptor-binding antibodies in 63%, and repetitive distal nerve stimulation showed decrement in 33%. The yield of serology and nerve stimulation tests increased with generalization of myasthenia and when proximal nerves were also tested. Ocular myasthenics responded to pyridostigmine bromide monotherapy, while generalized myasthenia required additional medical and/or surgical therapy. Patients receiving corticosteroids had thymectomy at a later date. Those with normal thymus had a greater chance of remission without medication than patients with thymic hyperplasia. [1]

COMMENT. Thirty-eight percent of these patients were in complete remission and without drugs when followed for more than 4 years (range, days to 20 years). The outcome was better for ocular than generalized myasthenia, 57% cf 30% in remission without drugs. A lower rate of remission in thymectomized (35%) compared to non-thymectomized (43%) patients was a reflection of disease severity and poor response to medication.

In a report of 35 juvenile myasthenics treated at the Massachusetts General Hospital, 86% of 21 who underwent thymectomy had complete or partial remission compared to 93% of 14 treated only with medication. A higher rate of complete remission and drug withdrawal was obtained in the thymectomized group, however (29% v 14%) [2]. The earlier the surgery, the better the chance of remission (see Ped Neur Briefs April 1992;6:30).