[A case of topographical disturbance following a left medial parieto-occipital lobe infarction].

A 59-year-old man was admitted to our hospital for his sudden-onset right hemianopsia. Thirty days after the onset, neuropsychological examination revealed obvious topographical disorientation and mild optic ataxia. Magnetic resonance imaging showed abnormal intensity area at the left medial parietooccipital region and left splenium of the corpus callosum. Although single photon emission CT showed uptake decrement in the left hemisphere, almost normal uptake was observed in the right hemisphere. He could recognize landmarks, but fail to recognize the relative position of landmarks. Therefore, his topographical disorientation was considered to be due to perceptual disturbance, memory disturbance of relative position of landmarks, or both. He was right-handed with no sinistral relative, and showed dyslexia and dysgraphia early in his clinical course. The laterality index of the dichotic listening test revealed the right ear dominance. These results indicated that his left hemisphere was language dominant. His topographical disorientation could be caused by the medial parieto-occipital lesion in the dominant hemisphere.