"Myasthenic Snarl"

"Myasthenic Snarl"

Patients with weakness of facial musculature as a consequence of myasthenia gravis may have a "transverse smile", with lack of elevation of the corners of the mouth, or appear to snarl when asked to smile or laugh. This may give the impression that they seem peculiarly unamused by an examiner’s attempted witticisms. These phenomena may be seen with other causes of facial weakness, such as facioscapulohumeral (FSH) dystrophy.