To report a case of idiopathic unilateral abducens nerve palsy in an adolescent patient.

A healthy 14-year-old boy presented with binocular horizontal diplopia that started that same day. He did not have any history of trauma, vaccination or infectious disease and showed no other neurological signs. The best corrected visual acuity of both eyes was 20/20. Slit lamp and fundus examinations revealed no other abnormalities. On the alternative prism cover test, he had 6 prism diopter (PD) esotropia with −1 degree abduction limitation in the left eye. After 1 week, the abduction limitation in the left eye was progressed to −3.5 degrees, so we performed brain imaging. The brain magnetic resonance imaging (MRI) and systemic evaluation (serologic test, cerebrospinal fluid examination) were normal therefore, we suspected idiopathic unilateral abducens nerve palsy. Thus, intravenous steroid injection was started, and the patient was partially recovered after 5 days of treatment. At 5 weeks after presentation, diplopia and abduction limitation in the left eye were completely resolved, and recurrence was not found during the 1 year of follow-up.

We report a case of progressive idiopathic unilateral abducens nerve palsy in an adolescent which has resolved completely after intravenous steroid treatment in a short period.