Cogan Lid Twitch

A 50-year-old woman presented with ptosis of her left eyelid for 6 months. Several exam findings including variable and fatigable ptosis, and Cogan lid twitch, raised suspicion for Myasthenia Gravis. Acetylcholine receptor binding, blocking, and modulating antibodies were negative, and single fiber EMG was normal. MRI brain/orbits without and with contrast was unremarkable. There was no evidence of thymoma on chest CT. Diagnosis of Myasthenia was ultimately confirmed with positive ice pack test, positive edrophonium (Tensilon) test, and suggestive history and exam findings. The patient was started on Pyridostigmine 60mg 5 times daily, to which she responded well, but stopped it a year later on her own with resolution of diplopia and ptosis. The video displays a Cogan lid twitch of the patient's left eyelid. First described by Dr. David G. Cogan in 1965, the Cogan lid twitch (CLT) is a sign of Myasthenia Gravis and can be elicited by having the patient initially maintain downward gaze and then look up to the primary position. The lid will show a brief upward twitch. Cogan theorized that this sign could be explained by the quick fatigability and rapid recovery of the myasthenic levator palpebrae superioris. The downward gaze allows for relaxation of the muscle which allows for recovery once the patient looks straight ahead. As the elevation is only maintained for a brief period, it appears as a twitch [1]. The specificity of the CLT has been reported as 99% and sensitivity as 75% in one study [2]. [1] Cogan DG. Myasthenia Gravis: A Review of the Disease and a Description of Lid Twitch as a Characteristic Sign. Archives of Ophthalmology. 1965;74(2):217-221. doi:10.1001/archopht.1965.00970040219016 [2] Singman E; Matta N; Silbert DI. Use of the Cogan Lid Twitch to Identify Myasthenia Gravis. Journal of Neuro-Ophthalmology. 2011;31(3):239-240 doi:10.1097/WNO.0b013e3182224b92