Clinical, electrophysiological and immunological remissions after thymectomy in myasthenia gravis

Objectives : Approximately 50% of patients treated with thymectomy have a chance for symptom-free life. However, immunological and neurophysiological abnormalities may be detected in patients with clinical remission. Although improvement usually parallels decrease in acetylcholine receptor antibody (AChRAb) levels and jitter values, there is a question what factors influence immunological and electrophysiological remission in a population of myasthenia gravis (MG) patients. Methods : We analyzed retrospectively clinical data of 32 MG patients operated for generalized MG, followed-up at our department for 17.2 (4–31) years. They were in clinical remission for 12.8 (2–25) years. All of them had single fiber electromyograhy (SFEMG) of extensor digitorum communis muscle (EDC) muscle and estimation of AChRAb level at the end of follow-up. Their age at onset of MG was 17 years (6–48) and at thymectomy 19 (6.4–58) years. Tensilon test was positive in 30, repetitive nerve stimulation in 29 cases. Results : Clinical remission was reached on average 4.2 years after thymectomy. SFEMG jitter value normalized in 60% of cases. AChRAb were negative only in 34% of patients. Jitter values correlated with AChRAb levels ( P =0.006, r =0.5) but were not related to clinical factors. Only time to thymectomy correlated with time from thymectomy to clinical remission ( P =0.001, r =0.5). Conclusions : Clinical remission is not always accompanied by normalization of SFEMG and AChRAb. Although normalization of neuromuscular transmission in patients with remission of MG is individual, short duration of MG before thymectomy increases the chance of early remission.