Teaching Video NeuroImages: Resolution of Ptosis After Forceful Eye Closure: Bedside Diagnosis of Myasthenia Gravis.

A 72-year-old man presented with fluctuating right eyelid ptosis. During sustained gaze fixation without blinking, the blepharoptosis progressively increased to almost complete ptosis, because of fatigable weakness of the levator palbebrae superioris (LPS) muscle. Noticeable is the eyebrow lifting due to compensatory frontalis muscle contraction (figure). The patient was asked to close his eyes forcefully for 30 seconds (Bienfang test) (figure). Immediately the ptosis resolved (figure; video). During maximal voluntary contraction of the orbicularis oculi (OO), the antagonistic LPS is inhibited and relaxes. On eyelid opening, the LPS is fully recovered, while the OO is fatigued. The sensitivity and specificity of the Bienfang test is 94% and 91%, respectively.1,2 The diagnosis was acetylcholine receptor–positive ocular myasthenia gravis.