A Syndrome of Pathological Left-handedness

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Abstract
• A pattern of correlative changes in lateralization in individuals with known or suspected brain injury recently has been advanced as the syndrome of pathological left-handedness (PLH). This syndrome, which is believed to be caused by an early left-sided cerebral lesion, may include asymmetric motor and/or trophic changes on the right side of a body part in addition to changes in higher-level cognitive processing abilities. Several clinical case studies have provided support for such a syndrome. Despite their clinical importance, such case studies are unfortunately subject to inherent biases of selection. The present study was therefore designed to evaluate the PLH syndrome in a systematic fashion by using a large number of brain-injured and normal subjects. The incidence of each of the putative elements of the PLH syndrome was investigated. The results suggest that traits such as atypical cerebral speech representation, motor impairment of the nondominant hand, and hypoplasia of the right foot are salient features of the syndrome. The results are discussed with reference to clinical diagnostic implications.