Pathological Left-handedness Syndrome

Let’s be absolutely clear: simple or normal left-handedness is not a syndrome. It is simply a trait that affects about 10 percent of every population. I am one of them.

But some left-handedness is the result of an early suspected brain injury. Research indicates that several changes can occur if a hemispheric lesion has been inflicted that is predominantly left-sided (or bilateral asymmetric), which onsets before Age 6, and which encroaches upon the critical speech zones of the frontotemporal/frontoparietal cortex.

The pattern of changes may include any or all of the following features: shifts in manual dominance, trophic changes in the extremities, transfer of hemispheric speech, and/or intrahemispheric reorganization of visuospatial cognitive functions[1]. Further research 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 Pathological Left-handedness Syndrome[2].

[2] Satz et al: The pathological left-handedness syndrome in Brain and Cognition - 1985
[1] Orsini et al: A Syndrome of Pathological Left-handednessCorrelates of Early Left Hemisphere Injury in Archives of Neurology - 1986