(Edmonton) Stroke victims may have a longer window of opportunity to receive treatment to save their brain cells, a literature review published by University of Alberta medical researchers in Lancet Neurology demonstrates.
The review, which was published online Sept. 20, was written by Ashfaq Shuaib and his colleagues, including Ken Butcher, an assistant professor of Neurology. Shuaib, the senior author, is a researcher in the Division of Neurology with the Faculty of Medicine & Dentistry. He is also a practising neurologist and a stroke specialist.
Shuaib reviewed stroke studies that examined the use of imaging to measure blood flow in the brain after a stroke. The literature was written from 1980 to July 2011. His review notes that using advanced neuroimaging, such as multi-dimensional brain CT scans and MRIs, can provide physicians important information about blood flow in the brain following a stroke. This information could enable doctors to provide better treatment to prevent brain cells from dying, through the use of techniques to increase blood flow in the brain.
The review noted that the presence of good "collateral" blood flow in the brain can "sustain brain tissue for hours" after major arteries to the brain have been affected by a stroke, and this flow could potentially offset injury to the brain. Enhancing or maintaining strong blood flow is a potential therapeutic treatment for stroke; it is currently under investigation in several stroke centres around the world, says Shuaib.
His review notes that stroke is the second most-common cause of death, with the majority of the 16 million cases happening in developed nations. A lack of blood flow is the primary cause of a stroke. It is typically triggered by a blockage in a brain artery due to arteries thinning from a build-up of plaque, or by a mass from the heart or neck vessels restricting blood flow to the brain.
Normal blood flow in the brain is between 50-60 ml/100g/minute. If someone suffers a stroke and blood-flow levels in the brain fall below 10 ml/100g/minute, brain cells die within minutes of the stroke. However, if blood flow in the brain is between 10-20ml/100g/minute, "the neurons cease function but remain structurally intact and are potentially revivable if normal blood flow is restored," Shuaib says in the review.
He further adds that brain-cell death after a stroke may not be complete for hours or even days after a stroke, meaning that the window to treat some stroke patients is longer than three hours�the standard timeframe that has been referenced in medicine since the 1990s. Shuaib says cell death can be complete within as little as an hour in some people following a stroke, while other patients have viable brain tissue and cells for days or indefinitely after a stroke. And with current imaging technology, physicians can determine whether brain cells are dead or have simply ceased functioning post-stroke.
"What we're recommending is, don't look at the window of time only, look at the important tissue window which may be quite prolonged in many patients," says Shuaib. "Don't just say, 'oh this person had a stroke 4.5 hours ago, end of story.' This person may have very good tissue you could treat."
Charles Carnell is a recovering stroke patient who had strong collateral blood flow after he suffered a stroke in July. His treating neurologist was Ken Butcher, who worked on the review.
"Charles was very fortunate; he actually had collateral flow keeping much of his brain temporarily alive on one side and salvageable," says Butcher. "We were very optimistic, given what we saw on the scans about Charles' brain, that we would be able to salvage a lot of his brain and in fact that's exactly what happened. We were able to open up that blockage and Charles began to recover within a couple hours of us giving him the drug.
"He is now at home and independent, which is really the best we can hope for after someone has a stroke."