The Gerstmann syndrome, or angular gyrus syndrome, consists of acalculia, agraphia (of central type), finger agnosia, and right-left disorientation; there may in addition be alexia and difficulty spelling words but these are not necessary parts of the syndrome. Gerstmann syndrome occurs with lesions of the angular gyrus and supramarginal gyrus in the posterior parietotemporal region of the dominant (usually left) hemisphere, for example infarction in the territory of the middle cerebral artery.
All the signs comprising Gerstmann syndrome do fractionate or dissociate, i.e., they are not causally related, or representative of a unitary neuropsychological function, as was once suggested. Nonetheless the Gerstmann syndrome remains useful for the purposes of clinical localization.
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