Affiliations: Johns Hopkins University School of Medicine,
Baltimore, MD, USA | Kennedy Krieger Institute, Baltimore, MD, USA
Note: [] Address for correspondence: Argye E. Hillis, MD, MA, Associate
Professor of Neurology, Johns Hopkins University School of Medicine, Johns
Hopkins Hospital, Phipps 126, 600 N. Wolfe Street, Baltimore, MD 21287, USA.
Tel.: +1 410 614 2381; Fax: +1 410 614 9807; E-mail: [email protected]
Abstract: Several studies have demonstrated reorganization of cognitive and
motor function caused by stroke. This study examined the influence of
hypoperfused brain regions, in addition to the area of the infarct itself, on
reorganization of the cognitive processes underlying word generation in stroke
patients. In addition, we also sought to determine the influence of
hypoperfusion on the blood oxygen level dependent/(BOLD) effect. Subjects with
left and right subacute or chronic subcortical strokes, along with normal
controls, were imaged while performing a verbal fluency task (word generation).
The study population included six normal subject and six stroke patients with
subcortical infarcts and cortical hypoperfusion in the middle cerebral artery
territory who had recovered or improved markedly in word fluency. While normal
subjects displayed a left-lateralized fronto-temporo-parietal and bilateral
cingulo-striatal-thalamic-cerebellar network, the activation pattern of stroke
patients was determined both by the hypoperfused regions and infarcted
areas of the brain. Specifically, patients showed diminished BOLD effect in the
cortical regions that were hypoperfused, even though their infarcts were
subcortical, and showed increased BOLD effect in the homologous regions of the
normal hemisphere. This finding raises the possibility that cortical
hypoperfusion in the absence of infarct can cause shift of language functions
to the opposite, intact hemisphere. However, reduced BOLD effect in the task
relative to rest was found in hypoperfused regions in two patients, raising the
possibility that regional function persisted, even though vascular reactivity
was impaired. Results illustrate the complexities of functional imaging studies
of recovery in patients with vascular lesions.
