Teaching Video NeuroImage: The "Chameleon Eyes Sign" in Myasthenia Gravis

A 57-year-old man was admitted to the intensive care unit for dysphagia and respiratory failure in the context of bilateral pneumonia. After improvement with antibiotics, he developed fluctuating diplopia. Ocular examination showed intermittent exotropia of one or both eyes elicited by sustained gaze in different directions (Video 1). Acetylcholine receptor antibodies were detected (fixed cell-based assay), confirming myasthenia gravis (MG).1 The patient was treated with intravenous immunoglobulins (2 g/kg over 5 days), followed by oral prednisone (25 mg/d) with symptom resolution. Fatigable exotropia due to selective weakness of the medial recti may occur in MG,2 resembling the independent eye movements of a chameleon.