An unusual chiasmal visual defect in a patient with neuromyelitis optica: case report.

PURPOSE To report the unusual visual field finding due to a chiasmal neuritis in a 33-year-old female with the diagnosis of optic neuromyelitis optica (Devic's syndrome). METHODS We report a case of a 33 years old female with limb paraesthesias, weakness in the legs, bowel and bladder dysfunction that was referred to the "Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo" in October 1995. Six years and four months later she had an acute visual involvement. Ophthalmologic examination, laboratory studies, magnetic resonance imaging (MRI) and a 24-2 threshold visual field in the Humphrey field analyzer were performed. RESULTS The MRI scan showed enlargement and cavitation on the spinal cord and chiasmal involvement (thickening of the chiasm with contrast enhancement) and no demyelinating lesions in the brain, brainstem, or cerebellum. The central 24-degree threshold field examination showed an inferior visual field defect bitemporally, disclosing a chiasmal involvement. CONCLUSION Chiasmal involvement may occur in neuromyelitis optica, probably due to a plaque within the chiasm. The authors call attention to the importance of visual field examination with particular regard to quantifying the visual impairment and follow-up of these patients.