Topographic disorientation: two cases.

Topographic disorientation is very rare, and usually occurs as a result of a right occipitotemporal lesion. The substrates accounting for these symptoms are thought to be the right parahippocampal and lingual gyri. I report two cases of topographic disorientation. Patient 1, a 58-year-old male taxi driver, suddenly lost his way while driving home. At presentation he could neither describe nor draw a route from one place to another. This patient gradually regained his topographic orientation over the course of 3 months. Patient 2, a 58-year-old male farmer, suffered a headache and visual hallucinations, and subsequently lost his bearings. He could describe and draw a map of a route in detail, although the streets that he traveled daily appeared strange to him. The topographic disorientation of patient 2 had changed little 3 years after the onset. Both patients had left homonymous hemianopia, but no prosopagnosia, constructional apraxia, unilateral spatial neglect, or other cortical dysfunction. Brain computed tomography revealed an infarct of the right posterior cerebral artery, involving the cuneus and lingual gyri, in both patients. The lesion was located more dorsally in patient 1, involving part of the right parietal lobe, and more ventrally in patient 2, involving the right parahippocampal gyrus, which might account for the discrepancy between their topographic orientation and the clinical course.