Parry Romberg Syndrome Presenting as an Isolated Sixth Nerve Palsy

A twenty-three-year-old woman noted the onset of horizontal diplopia, worse on the left gaze than right, not correlated with time of day or activity. She initially presented to an optometrist who diagnosed her with stress, and prescribed reading glasses. Her diplopia worsened, so she consulted a strabismus specialist who diagnosed her with left 6th nerve palsy, and she underwent surgical correction. MRI at this time was normal. Acetylcholine receptor antibody titers were negative. She developed progressive left upper lid ptosis and was referred to a neuro-ophthalmologist for evaluation of possible ocular myasthenia.