Crossed nonaphasia in a dextral with left hemispheric lesions - A functional magnetic resonance imaging study of mirrored brain organization

Background-General conclusions concerning mechanisms of cerebral lateraliza tion may be learned from the investigation of functional brain organization in patients with anomalous lateralization. Case Description-The functional organization of language, attention, and mo tor performance was investigated in a 42-year-old patient with crossed nona phasia by means of functional MRI. The strongly right-handed man experience d a left middle cerebral artery infarction documented by MRI without exhibi tion of aphasia. However, the left hemispheric stroke was accompanied by vi suospatial impairment, right-sided slight sensory and motor paresis, and ri ght homonymous hemianopia. No history of familial sinistrality or prior neu rological illness was present. Functional MR language mapping revealed stro ng right hemispheric activation in inferior frontal and superior temporal c ortices. Finger tapping with the right hand recruited ipsilateral premotor and motor areas as well as supplementary motor cortex. A Stroop task, usual ly strongly associated with left-sided inferior frontal activation in dextr als, resulted in strong right hemispheric frontal activation. Conclusions-From our data there is clear evidence that different modalities , such as language perception and production, attention, and motor performa nce, are processed exclusively by I hemisphere when atypical cerebral domin ance is present.