[Neurophysiological parameters in myasthena gravis in children in diagnostic and therapeutic view].

Background: Myasthenia gravis (MG) is an autoimmunologic disorder. It is characterized by various clinical symptoms and their dependency upon the exertion and the rest as well.

Material and methods: Between 2002-20014 in the Neurophysiology Laboratory at the Chair of Pediatric and Adolescent Neurology, Jagiellonian University in Krakow, the electrophysiological repetitive nerve stimulation study were performed in 44 children. The clinical picture and positive electrophysiological test were the ground to diagnose MG in 19 of them (12 girls and 7 boys). The mean age at onset of MG in the examined group was 12.8 years. In 5 patients the diagnosis was completed using edrophonium test. In 14patients the titer of AchRAb was also tested. In 18 patients with MG the radiological examinations of the chest were performed. In 14/19 patients with MG the control electrophysiological testing was performed 2 to 8 months after the first one.

Results: The gen-ralized MG was diagnosed in 14 patients, and ocular in 2 of them. The amplitude of electro-physiological testing was normal during the first response in all patients, but the decrement of amplitude 4:1 in patients with MG was 26% to 88%. In 3 patients with MG the persisted thymus, while in 7 hypertrophy of thymus, in 2 thymoma nad inl thyinflammation of the thymus was detected. In 5 children the result of chest examination was normal. Among 5/8 patients (62.5%) with positive AChRAb, in one ocular MG was diagnosed, in the other 7 generalized MG. The titer of AChRAb was between 0.4 and 30.8 nmol/l (mean 9.44 nmol/l), and the decrement of amplitude 4:1 was 22% to 58%.. In the treatment pirydostygmine bromide (Mestinon) was used in all children, however in 4 of them together with azathioprine, and in 7 with steroids. In the treatment of myasthenic crisis in 5 patients plasmapheresis was performed. In 42% of patients thymectomy was performed during the first year after diagnosis. The clinical remission was succeed in 90,9% patients. The electrophysiological control examination detected the decrement of amplitude 4:1 in 1% to 80% (mean 36%). The electrophysiological remission, correlating with clinical remission was achieved in 2 patients. In 6/10 patients with clinical remission, the decrement of amplitude 4:1 in electrophysiological examination continued to be at the level similar to initial examination. In 1 patient remission was complete allowing significant reduction of doses of Mestinon, even though in the electrophysiological test the decrement was 80%.

Conclusions: (1) Among hospitalized children, the generalized myasthenia was the most common. (2) Neurophysiological studies plays still fundamental role in diagnostic methods in the diagnosis of myasthenia gravis in children. (3) The correlation of the clinical state and electrophysiological results was not established.