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[[File:Triple -furrow (1).jpg|thumb|Triple furrow tongue in a patient with AchR antibody positive, non-thymomatous, bulbar predominant MG. The furrowing resolved after treatment including thymectomy, prednisone, and mycophenolate.]]The triple furrow, or trident, tongue is a rare but characteristic manifestation of MG in which a midline and two parallel longitudinal grooves appear in the tongue.(1) The unusual furrowing pattern is usually accompanied by tongue atrophy. Muscle atrophy is not typically part of MG. Tongue and facial muscle atrophy occurs more commonly in the MuSK (muscle specific tyrosine kinase) variant of the disease. MG with MuSK antibodies is a subgroup of seronegative MG characterized clinically by severe, predominantly faciobulbar weakness and the frequent occurrence of atrophy of the tongue and facial muscles.(2) It is much more common in females. MuSK antibodies are present in about 70% of patients with seronegative MG.
Tongue atrophy, as well as atrophy of other muscles, apparently occurred more often in the past before effective therapies were available and patients sometimes had severe, long-standing, poorly controlled MG. Many reports of muscle atrophy in MG date from a time before MuSK, or even AchR antibodies, were described. Disuse and functional denervation have been postulated as the explanation for the muscle atrophy.(3,4)
