Homonymous quadrantic visual field defect resulting from vertebrobasilar insufficiency: report of a case.

A patient showing a congruous homonymous superior quadrantanopsia was found at autopsy to have infarction of the striate cortex. The lesion involved the inferior bank of the calcarine fissure almost entirely and approximately one fifth of the superior bank. Additionally, infarctions of the visual association cortex and the pontine tegmentum were found. No lesions in the corresponding temporal lobe were present. Two types of visual field defects have been described in association with occipital lobe lesions: a monocular temporal crescentic defect if the lesion is anterior and a congruous homonymous hemianopsia if it is posterior. This patient seems to represent a variant of the latter. The most prominent difference with respect to quadrantanopsias resulting from lesions of the optic radiation is the high degree of congruity, especially in the central portion of the field. Association with nonocclusive vascular events related to vertebrobasilar hypoperfusion rather than embolization is also more common.