Quantitative CT scan studies in aphasia: II. Comparison of the right and left hemispheres

Quantitative information about the right and left hemispheres (RH and LH) on CT scans of 32 aphasic stroke patients (A's) and 10 nonaphasic controls (NC's) within a similar age range was obtained with a semiautomated computer program written to analyze CT scans. There was significant increase in the RH %LoPix (pixels related primarily to ventricular areas) for the A's (especially global aphasics) as compared to the NC's. This was not related to midline shift, but may have been related to age, diaschisis (postlesion shock), or transsynaptic degeneration. Distinctive tissue-loss profiles were generated which reflected LH %LoPix (pixels related to infarct plus ventricular area) minus RH %LoPix at each CT slice for six aphasia types. These quantitative profiles (L - R %LoPix) were used with 89–100% accuracy in discriminant-analysis classification of aphasia groups when anterior/posterior lesion locus was controlled for. Significant correlations were obtained between severity of aphasia and L - R %LoPix. The overall percentage midline shift (right to left) for the A's was 2.4% (NC's, 0.8%). The globals showed the least amount of shift, and the transcortical motor and Broca's showed the most at the lower slices (B and B W ), while the Wernicke's showed the most at the higher slices (W and SM). The CT numbers in the remaining tissue (nonlesioned areas) were also studied. This right- and left-hemisphere analysis provided insight into the dynamics of the gross morphological reaction of both hemispheres to the presence of a unilateral infarct.