Brain Bypass Surgery Leads to Restoration of Lost Brain Tissue

A new study shows that surgical revascularization can reverse cerebral cortical thinning in patients with severe cerebrovascular steno-occlusive disease.

Researchers at Toronto Western Hospital (Canada) identified 29 patients who had undergone brain revascularization following cerebrovascular disease who had both pre- and post-operative studies of their cerebrovascular reactivity using blood oxygen level-dependent magnetic resonance imaging (MRI). Cortical thickness in regions corresponding to steal physiology--and where applicable corresponding areas in the normal hemisphere--were measured using specialized software.

The results showed that at an average of 11 months after surgery, cortical thickness increased in every successfully revascularized hemisphere. Mean cortical thickness in the revascularized regions increased by 5.1%, demonstrating successful regional revascularization and reversal of steal physiology, followed by restoration of cortical thickness. The study was published early online on April 14, 2011, in the journal Stroke.

"We were pretty astounded when we saw the results because they were quite unexpected. Our goal with the surgery was to halt further loss of brain tissue due to strokes, so it was remarkable to see the loss was actually reversed,” said corresponding author neurosurgeon Michael Tymianski, MD. "The regrowth of brain tissue has only been observed in an extremely limited number of circumstances. We consider this so important because one of the most important health issues facing our population is chronic cerebrovascular disease, which leads to neurocognitive impairment and reduces quality of life.”

Chronic deficiencies in regional blood flow lead to cerebral cortical thinning without evidence of gross tissue loss, as well as potentially negatively impacting cognitive and neurological performance. This is most pronounced in patients with severe occlusive cerebrovascular disease in whom affected brain areas exhibit "steal physiology," a paradoxical reduction of cerebral blood flow in response to a global vasodilatory stimulus intended to increase blood flow.

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