Pure topographical disorientation: a definition and anatomical basis.

Four patients showing the syndrome of "topographical disorientation" are reported. Patients became unable to find their way, especially in unfamiliar surroundings, following a single lesion in the territory of the right posterior cerebral artery, as evidenced on CT-scan. Associated disturbances included: left hemianopia, mild face recognition problems, and various degree of impairment in face-learning and visual maze-learning tasks. Language, visuo-perceptive and constructional abilities, object and picture recognition were intact. Memory tests only showed a mild, generally non-significant, impairment of visual memory. As inferred from the lesion located in the 4 patients, this syndrome seems to be strongly related to damage to the right parahippocampal gyrus, a structure that thus appears crucial for specifically storing and/or retrieving visual information necessary to achieve orientation in the locomotor environment.