A PET follow-up study of recovery after stroke in acute aphasics

The neural correlates of recovery from aphasia are largely unknown. Several different sources of evidence, from clinical studies to neurophysiological investigations, have suggested a contribution of the contralateral, undamaged hemisphere in recovery from aphasia. Eight patients with unilateral left hemispheric stroke were submitted to a standard language examination and to a [18F]FDG PET study in the recent phase after stroke (within 2 weeks) and 6 months later. All patients had a substantial recovery of specific aspects of language functions at the follow-up. Analysis of regional glucose metabolism showed hypometabolism in structurally unaffected regions both in the left and in the right hemisphere (diaschisis), in the acute stage. Glucose metabolism increased significantly on both sides in all patients at the second PET study. Regional analysis showed significant positive correlations between changes in metabolic values in several cortical and subcortical regions in the right hemisphere and changes in language performance at follow-up. The present findings show that an extensive, bihemispheric depression of metabolism is found in the acute stage after stroke in aphasic patients. Language recovery in the first months after aphasia onset is associated with regression of functional depression (diaschisis) in structurally unaffected regions, in particular in the right hemisphere.