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EMBARGOED FOR RELEASE UNTIL 9:45 AM, THURSDAY, APRIL 30, 1998
Brain Repairs, Reorganizes to Regain Speech Following Stroke A new study shows how the brain works to repair and reorganize itself to recover lost speech capabilities after a stroke.
To repair itself, the brain reorganizes damaged speech-processing areas and, when necessary, activates other areas to compensate for permanent damage, according to a study released during the American Academy of NeurologyÃs 50th Anniversary Annual Meeting, April 25 - May 2, in Minneapolis, MN.
The study involved 12 patients with acute ischemic left-hemispheric stroke (a blocked blood vessel, causing loss of blood flow to areas on the left side of the brain) and aphasia (loss of use or comprehension of words). Researchers used magnetic resonance imaging (MRI) to show brain anatomy and positron emission tomography (PET) to show brain activity. Seven of the patients were evaluated again one year after stroke.
"Speech is primarily regulated in the left cerebral hemisphere. Recovery from an acute ischemic stroke in that territory depends on the brainÃs ability to reorganize the disrupted speech network," said study co-author Hans Karbe, MD, University Hospital Department of Neurology, Cologne, Germany.
The brain initially tries to cope by reorganizing the damaged left hemisphere and stimulating speech processing in intact areas, Karbe said. When the left-hemispheric speech centers are severely and permanently impaired, the brain recruits right-hemispheric regions to recuperate language function.
Patients who have speech recovery in the brainÃs left hemisphere have better results and long-term prognosis than those with permanent speech activation in the right hemisphere. Karbe explains, "During brain development, some neurons of the left hemisphere irreversibly gain more speech-competence, while there is an irreversible loss of potential speech-competent neurons in the right hemisphere. This consequently determines and limits the compensatory ability of the right hemisphere in the adult brain."
"Reorganization of the speech-relevant network is an ongoing process for at least several months, and possibly for more than one year after the ischemic brain injury," Karbe said. "The long period of neural reorganization opens a wide time window for language training in these patients."
Stroke affects about 700,000 Americans each year. It is the third-leading cause of death and the leading cause of adult disability.
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