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Abstract:
We previously reported that, in acute stroke (n=22), specific
lexical deficits were correlated with distinct regions of
hypoperfusion on MR perfusion imaging (MRPI). We replicate these
findings in a larger population (n=56), and evaluate whether
reperfusion of these regions results in recovery of associated
functions. Methods: Subjects were tested within 24 hours of aphasia
onset, with MRPI (which shows foci of hypoperfusion),
diffusion-weighted imaging (DWI, which shows infarct at onset), and
a lexical battery (oral and written naming, oral reading,
dictation, written and spoken word comprehension, lexical decision,
and repetition; 34 items each). Performance across lexical tasks,
and error types, were used to identify which lexical processes were
impaired. Using published templates and MRPI+DWI scans, 10 areas
were examined for hypoperfusion or infarct. Results: associations
between lexical impairment and site of hypoperfusion or infarct
included: orthographic input lexicon and angular gyrus (r=.39; p
<.01); semantics and Wernicke's area (r=.86; p<<.00001);
and phonological output lexicon and posterior midtemporal gyrus
(r=.62; p=.00001). Eight patients received intervention, resulting
in reperfusion. Reperfusion of Wernicke's area resulted in
resolution of semantic deficits (5/5 cases); reperfusion of
posterior midtemporal gyrus resulted in recovery of
phonological-lexical output (3/3 cases). Thus, poor perfusion of
discrete regions resulted in specific lexical deficits, and
reperfusion of two of these regions resulted in recovery of
associated lexical functions, indicating these regions were
essential for specific lexical functions.
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