title: Fourth nerve paresis and ipsilateral relative afferent pupillary defect without visual sensory disturbance. A sign of contralateral dorsal midbrain disease.
abstract: We describe a patient with a left trochlear nerve paresis and a left relative afferent pupillary defect despite normal visual acuity, color vision, visual fields, and fundus examination. Magnetic resonance imaging revealed a lesion in the right dorsal midbrain extending from the brachium of the superior colliculus to the inferior colliculus. The anatomy and physiology of the pupillary light reflex are reviewed, as are possible mechanisms for the laterality of afferent pupillary defects with midbrain lesions. The presence of a trochlear nerve paresis with an ipsilateral relative afferent pupillary defect and an otherwise normal ophthalmic exam indicates a lesion in the contralateral dorsocaudal midbrain.
authors.affiliation: Neuro-Ophthalmology Unit, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, MD 21205.
authors.forename: D
authors.initials: D
authors.lastname: Eliott
authors.forename: E T
authors.initials: ET
authors.lastname: Cunningham
authors.forename: N R
authors.initials: NR
authors.lastname: Miller
mesh_terms: D000328:Adult; D001254:Astrocytoma / Q000150:complications* / Q000503:physiopathology; D001932:Brain Neoplasms / Q000150:complications* / Q000503:physiopathology; D003389:Cranial Nerve Diseases / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008636:Mesencephalon / Q000503:physiopathology; D010243:Paralysis / Q000209:etiology* / Q000503:physiopathology; D011681:Pupil Disorders / Q000150:complications / Q000209:etiology*; D014321:Trochlear Nerve / Q000503:physiopathology