Thymectomy in juvenile ocular and generalized myasthenia

Purpose: Because the role of thymectomy in juvenile ocular and generalized myasthenia is unclear, we reviewed the treatment and outcomes of juvenile myasthenia patients seen at the University of Iowa Hospitals and Clinics. Methods: A computer assisted search of medical records at the University of Iowa Hospitals for the period of 1966 to 1994 was made for all the patients with the diagnosis of myasthenia gravis with the onset before age 18. Features of the cases retrospectively reviewed included presenting symptoms, positive confirmatory tests, response to medical or surgical therapy, age of onset, duration of symptoms prior to thymectomy and rates of remission. Results: The major presenting symptoms for the group were ptosis (88%), generalized weakness (73%), diplopia or ophthalmoparesis (46%), and bulbar symptoms (38%). Positive confirmatory tests were Tensilon or prostigmine test in 18/18 (100%) with generalized myasthenia and 4/5(80%) with ocular myasthenia; AChR antibodies in 9/13 (69%) with generalized myasthenia and 2/4 (50%) with ocular myasthenia; repetitive nerve stimulation in 12/17 (70%) with generalized myasthenia and 0/4 (0%) with ocular myasthenia. Complete remission occurred in 5/17 (29%) of generalized myasthenia patients receiving thymectomy and in none of the generalized myasthenic patients without thymectomy. Complete remission occurred in 3/4 (75%) ocular myasthenia patients without thymectomy and in only 1/2 (50%) of ocular myasthenia patients with thymectomy. Outcome of other ocular myasthenic patients was pharmacologic remission in 1/2 (50%) with thymectomy and residual symptoms with pharmacologic therapy in 1/4 (25%) without thymectomy. Additional outcome of generalized myasthenia patients with thymectomy was pharmacologic remission in 6/17 (35%); residual symptoms with pharmacologic therapy in 3/17 (18%) and without therapy in 1/17 (6%); and unknown in 2/17 (12%). Conclusions: Tensilon and prostigmine test provided the highest yield of diagnostic studies to confirm the diagnosis of juvenile ocular and generalized myasthenia. Repetitive nerve stimulation studies were helpful in confirming generalized but not ocular juvenile myasthenia. Complete remission in generalized myasthenia occurred only in patients receiving thymectomy, whereas in ocular myasthenia, complete remission occurred in a greater percentage of patients not receiving thymectomy.