Hypoperfusion of Wernicke's area predicts severity of semantic deficit in acute stroke.

Based on earlier findings that the presence of word comprehension impairment (a deficit in the meaning of words, or lexical semantics) in acute stroke was strongly associated with the presence of hypoperfusion or infarct in Wernicke's area, we tested the hypothesis that the severity of word comprehension impairment was correlated with the magnitude of delay in perfusion of Wernicke's area on magnetic resonance perfusion-weighted imaging. Eighty patients were prospectively studied within 24 hours of onset or progression of acute left hemisphere stroke symptoms, with diffusion-weighted imaging, perfusion-weighted imaging, and detailed language tests. For 50 patients without infarct in Wernicke's area, we found a strong Pearson correlation between the rate of errors on a word comprehension test and the mean number of seconds of delay in time-to-peak concentration of contrast in Wernicke's area, relative to the homologous region on the right. These results add further evidence for the crucial role of Wernicke's area (Brodmann's area 22) in word comprehension and indicate that the magnitude of delay on PWI may be a gross indicator of tissue dysfunction.

Reperfusion of specific brain regions by raising blood pressure restores selective language functions in subacute stroke.

We report a series of six single subject studies examining the effects of pharmacological blood pressure elevation on regional brain perfusion and language function. Previous reports indicate that hypoperfusion of specific brain regions, as delineated by magnetic resonance perfusion weighted imaging (PWI), is associated with disruption of selective lexical functions. On this basis, we hypothesized that reperfusion of the same regions, in the absence of infarct in that region, would restore the associated lexical function. We present five patients with impaired lexical-semantics associated with poor perfusion, but not infarction, of Brodmann's area 22 (BA 22), and one patient with impaired lexical-semantics and a superimposed deficit in retrieving the phonological representations of words, associated with poor perfusion Brodmann's area 37 (BA 37) as well as BA 22. Each patient was treated with induced blood pressure elevation to increase perfusion of the ischemic and dysfunctional tissue. Daily testing of naming and comprehension, with stimulus sets matched for frequency, familiarity, and length, showed improved lexical-semantics in the patients who showed reperfusion of BA 22 and improved oral naming (but not lexical-semantics) in the patient who showed reperfusion of BA 37. These cases illustrate that loss of function with hypoperfusion of a circumscribed area of the brain, and recovery of the same function with improved perfusion of that brain region, can reveal brain/language relationships prior to reorganization after brain injury.