MRI evidence of early muscle atrophy in MuSK positive myasthenia gravis.

Muscle atrophy, particularly of facial and bulbar muscles, seems to be a relatively common long-term consequence of musclespecific tyrosine kinase-myasthenia gravis (MuSK-MG), perhaps reflecting the chronic state of disease or long-term therapy with corticosteroids. We performed magnetic resonance imaging (MRI) to assess muscle wasting in the facial and bulbar muscles in two female MuSK-MG patients, with short duration of symptoms prior to diagnosis and prior to commencement of steroid therapy. The study revealed marked atrophy of temporalis, masseters, and lingual muscles with fatty replacement. MRI evidence of early muscle atrophy in MuSK-MG may indicate that MuSK antibodies per se may predispose to muscle atrophy.