Tongue myokymia due to microscopic polyangiitis

A woman in her 60s reported 'cramping' of her tongue, and examination showed continuous undulating movements of the right tongue typical of myokymia. MRI demonstrated compression of the right hypoglossal nerve and the right internal carotid artery by a soft tissue mass involving the right carotid space and hypoglossal canal. A biopsy of the mass was considered too dangerous, but anti-MPO-ANCA (myeloperoxidase specific antineutrophil cytoplasmic) antibodies were found positive, and a tentative diagnosis of MPO-ANCA-associated vasculitis (i.e., microscopic polyangiitis-MPA) was made. She was treated with intravenous corticosteroids and then oral prednisone. She did not tolerate rituximab, so was treated with cyclophosphamide, followed by azathioprine. Eight months later, MRI showed complete resolution of the lesion, and her anti-MPO antibodies became negative. Her tongue myokymia was greatly decreased, but had not completely resolved.