Unilateral Pupil Sparing: Viral Oculomotor Neuritis With Concomitant Vestibular Neuritis

Unilateral oculomotor nerve palsy is a common clinical condition with various etiologies, including aneurysm, diabetes mellitus, central nervous system (CNS) infections, pituitary tumors, and ischemic changes. Due to the plethora of possible causes, early and thorough investigation is essential for treatment. We report the case of a 45-year-old male who presented with left ptosis, vertigo, and blurry vision and was diagnosed with oculomotor neuritis. Past medical history (PMH) was significant for hyperlipidemia, diabetes, and chronic kidney disease. Patient imaging revealed chronic left cerebellar infarction but no acute changes. Significantly, he was experiencing intractable nausea, dizziness, and vomiting attributed to concomitant vestibular neuritis. Infectious etiologies of oculomotor neuritis are rarely reported. However, idiopathic vestibular and facial palsies are commonly attributed to viral infection. The patient was treated with a steroid taper for viral vestibular neuritis, with noticeable clinical improvement to his oculomotor neuritis manifestations. This postulates a common viral etiology uniquely causing both oculomotor and vestibular neuritis.