ID 371 – Single fiber EMG in patients with Myasthenia Gravis

Abstract

Background and objective Single fiber electromyography (SFEMG) is a valuable tool in the diagnostics of the neuromuscular transmission. The objective is to evaluate the sensitivity of SFEMG in Myasthenia Gravis (MG). Patients and methods The group of 143 patients suffering from MG was examined. Disease was classified as ocular in 26% cases, oculobulbar in 31% cases, and 43% had generalized form. The extramuscular axonal microstimulation technique and registration from the orbicularis oculi muscle was used for the SFEMG end-plate jitter measurement. Results Antibodies positivity (anti-AChR or anti-MUSK) was present in 127 patients (89%), but SFEMG was positive in 133 persons (93%). Twelve seronegative patients had positive SFEMG, on the contrary among 10 persons with negative SFEMG the diagnosis was confirmed in 6 cases by positive antibody assay. Only four seronegative patients had also negative SFEMG. The combined diagnostic positivity (antibody assay or SFEMG) was 97%. We did not find any correlation between severity of disease (measured by MGFA ADL score) or the clinical form and jitter abnormalities. Conclusion The SFEMG using extramuscular axonal microstimulation of the orbicularis oculi muscle has the high sensitivity and could be recommended as a reliable test for MG regardless of the severity and clinical form.