Brain SPECT imaging in transcortical aphasias: the functional status of the left perisylvian language cortex

Single photon emission computerized tomography (SPECT) with 99mTc-HMPAO was used to examine the functional status of the left perisylvian language cortex (PLC) in eight patients with transcortical aphasias (TAs) due to cerebrovascular accidents. According to the lesion location within the left hemisphere, the aphasic patients were divided into two groups: (a) patients with corticosubcortical lesions involving portions or the whole PLC (perisylvian group, n = 4); (b) patients with corticosubcortical lesions sparing the PLC (extraperisylvian group, n = 4). Results showed that, as expected, the perisylvian group had significant decrements in regional cerebral blood flow (rCBF) in structurally damaged regions of the left PLC, although some morphologically spared regions of the left PLC (Wernicke's area) also had perfusion defects in one patient. Among the extraperisylvian group, there was structural and functional damage to the posterior association areas, but two patients additionally had significant decrements of rCBF in morphologically spared regions of the PLC (Wernicke's area, sensorimotor cortex, Broca's area). These findings demonstrate not only that the left PLC may be structurally and functionally damaged among patients with TAs, but additionally suggest a major contribution of the right hemisphere in the mediation of residual language repetition.