One and a Half Syndrome on Physical Exam This 28 year old patient presented to clinic with vision loss in the left eye that had been fluctuating for about a year. Entering VA was 20/40 OD and counting fingers at 3 feet OS. An APD was noted in the left eye. EOM testing displayed a complete left gaze palsy OU with a right gaze palsy OS. However, the patient maintained the ability to converge both eyes. A nystagmus in far right gaze was present but was more evident on the follow up video. This very rare presentation is known as (Cogan’s) One and a Half Syndrome. It results from a lesion of the PPRF (paramedian pontine reticular formation) and MLF (medial longitudinal fasciculus), which causes a horizontal gaze palsy to one side and an internuclear ophthalmoplegia to the other. The result is that one eye is fixed (no horizontal movement) in either direction and the fellow eye shows only abduction with nystagmus in that gaze. The most common causes of this are tumors, strokes, and multiple sclerosis. There was also high suspicion for retrobulbar optic neuritis. MRI was ordered and the patient was admitted to the hospital, diagnosed with MS, and started on IV steroids for three days, followed by oral prednisone. Three weeks later the patient returned to clinic with significant improvement in EOM and cognitive function. Bennett & Bloom Eye Center @anterior_seg_rocks #OneAndAHalf #One #Half #Syndrome #PhysicalExam #clinical #video #ophthalmology #neurology
