P01.5 Menstrual fluctuation with jitter correlate in MuSK antibody-positive myasthenia gravis

Abstract

Background: In myasthenic females fluctuations in symptomatology during menstruation is often reported, but the means by which the clinical worsening or remission occurs is unknown. Objectives: Our goal was to determine if there is an electrodiagnostic correlate to the increasing symptoms experienced during a menstrual exacerbation and to determine if this fluctuation could be eliminated with the use of continuous birth control therapy. Methods: The patient is a 26-year-old female with myasthenia gravis associated with antibodies to muscle-specific tyrosine kinase (MuSK). Patient had voluntarily discontinued medications at the time of the initial consultation and reported daily fluctuation of ocular and bulbar weakness that worsened each month at the start of the placebo week of her birth control medication. Single fiber electromyography (SFEMG) was performed at the start of the placebo week, during a period of increasing weakness. A second SFEMG was then performed one month later, during her typical time of menstrual fluctuation, while taking the new birth control regimen. Results: The SFMEG of the frontalis muscle performed during the exacerbation was markedly abnormal demonstrating increased jitter with blocking in 8 pairs (20%) and increased jitter without blocking in 12 pairs (60%). The mean jitter vale was 99 ls. Repeat SFEMG on the continuous birth control therapy demonstrated increased jitter with blocking in 3 pairs (15%) and increase jitter without blocking in 12 pairs (60%) and normal jitter in 5 pairs (25%). The mean jitter value was 85 ls. Conclusions: Continuous birth control therapy can produce clinical and electrodiagnostic improvement in menstrual related myasthenic exacerbations.