Plasticity of language-related brain function during recovery from stroke

Background and Purpose-This study was undertaken to correlate functional re covery from aphasia after acute stroke with the temporal evolution of the a natomic, physiological, and functional changes as measured by MRI. Methods-Blood oxygenation level-dependent contrast and echo-planar MRI were used to map language comprehension in 6 normal adults and in 2 adult patie nts during recovery from acute stroke presenting with aphasia. Perfusion, d iffusion, sodium, and conventional anatomic MRI were used to follow physiol ogical and structural changes. Results-The normal activation pattern for language comprehension showed act ivation predominately in left-sided Wernicke's and Broca's areas, with late rality ratios of 0.8 and 0.3, respectively. Recovery of the patient confirm ed as having a completed stroke affecting Broca's area occurred rapidly wit h a shift of activation to the homologous region in the right hemisphere wi thin 3 days, with continued rightward lateralization over 6 months. Ln the second patient, in whom mapping was performed fortuitously before stroke, r ecovery of a Wernicke's aphasia showed a similar increasing rightward shift in activation recruitment over 9 months after the event. Conclusions-Recovery of aphasia in adults can occur rapidly and is concomit ant with an activation pattern that changes from left to a homologous right hemispheric pattern. Such recovery occurs even when the stroke evolves to completion. Such plasticity must be considered when evaluating stroke inter ventions based on behavioral and neurological measurements.