Functional MRI as a tool for assessing chiasmal visual defect in a patient with neuromyelitis optica

Bitemporal haemianopsia is the classic visual field defect of disorders that involve the optic chiasm, caused by the involvement of the crossing nasal-retinal fibres of each optic nerve. The cortical consequence of chiasmal abnormalities had previously been limited to congenital abnormalities as in an achiasmatic patient, in whom each eye projects to the ipsilateral hemisphere, 4 and in albinos, in whom most of the retinal ganglion cells cross to the contralateral side. 3 5 Our study, however, described the cortical consequences of acquired (adult) bitemporal haemianopsia, in which the nasal-retinal fibres are temporarily lost rather than misrouted.