Localizing Thalamomesencephalic Afferent and Efferent Pupillary Defects

A 42-year-old Algerian man presented for binocular oblique diplopia, hypersomnolence with drop attacks, bilateral hearing loss, and thoracic pain. He had a right thalamomesencephalic hemorrhage due to an underlying cavernous malformation treated with subtotal surgical resection. On neuro-ophthalmic examination, the patient had a left relative afferent pupillary defect and a right oculosympathetic efferent pupillary defect (i.e., Horner syndrome) in addition to other thalamomesencephalic eye and neurologic signs (right fourth nerve palsy, hearing loss, hemiparesis, and thalamic pain). Clinicians should recognize the localizing value of this unique constellation of mesencephalic afferent and efferent pupillary defects.