CALGARY, AB--(Marketwired - December 16, 2016) - Following a seizure, the sufferer will often experience a temporary period of disability. For example, if a seizure occurs in the motor cortex of the brain, the individual may experience weakness in one side of their body. These effects can last for minutes, hours, or in some cases even days. It's a phenomenon referred to as Todd's Paralysis -- and until now has been neither understood, nor treated. Using both animal and human data, researchers at the University of Calgary's Cumming School of Medicine recently discovered how seizures can cause Todd's Paralysis as well as the mechanism responsible for this phenomenon. Findings were recently published in the journal elife.
Using an advanced new tool designed to measure oxygen levels in tissues, researchers observed rat brains following a seizure.
"We were amazed to find that after the seizures ended, suddenly the level of oxygen in that area of the brain crashed and stayed down, just above zero, for over an hour," says Cam Teskey, PhD, professor in the Department of Cell Biology and Anatomy at the Cumming School of Medicine.
This is a huge amount of time for the brain to be starved of oxygen and it is the first time anyone has observed this phenomenon occurring in the brain following a seizure.
"Essentially what is happening is that the seizure itself starts a cascade of events that leads to a period of severely reduced blood flow and reduced oxygen in the brain," says Teskey.
Teskey along with PhD student Jordan Farrell went on to discover that an enzyme -- called COX2 -- is the main culprit responsible for Todd's paralysis.
Large blood vessels, such as arteries, are coated in smooth muscles that control their diameter. The researchers found that during a seizure, COX2 becomes extremely active and produces by-products that act on the arteries' muscles to cause them to constrict, which decreases the amount of blood and oxygen that flows through the vessel. When the researchers introduced a drug to block COX2 from activating, they were able to prevent the stroke-like event from happening altogether.
"This is extremely exciting," says Teskey. "Not only have we found an explanation for Todd's Paralysis, but we have effectively identified a way that it can be prevented."
In addition to this discovery in animals, Dr. Paolo Federico, associate professor in the departments of clinical neurosciences and radiology, used an MRI scanner to look at blood flow in the brains of epilepsy patients in hospital, within one hour of experiencing a seizure.
"In about 80 per cent of these patients, we saw significant reductions in blood flow following seizures," says Federico. "This result was striking -- and also very concerning."
To Federico, this result not only explains Todd's Paralysis, but he thinks it could also offer an explanation for why some people with epilepsy experience cognitive impairments following and even in between their seizures.
"It's possible that this reduction in blood flow could have a cumulative effect on the brain that over time can result in cognitive impairments," he says. He is however quick to caution that this discovery is in its infancy and that there is still much to learn.
"What we need now is to conduct a clinical trial with a large number of patients who demonstrate this blood flow reduction."
This study was funded by the Canadian Institutes of Health Research
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About the Cumming School of Medicine
The University of Calgary's Cumming School of Medicine is a leader in health research, with an international reputation for excellence and innovation in health care research and education. On June 17, 2014, the University Of Calgary Faculty Of Medicine was formally named the Cumming School of Medicine in recognition of Geoffrey Cumming's generous gift to the university.
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The Hotchkiss Brain Institute
The Hotchkiss Brain Institute (HBI) at the University of Calgary consists of more than 120 scientists and clinician-scientists who are dedicated to advancing brain and mental health research and education. The Institute's research strengths, in the areas of Brain & Behaviour, Neural Injury & Repair and Healthy Brain Aging, are leading to new treatments for neurological and psychiatric disorders, aimed at improving quality of life and patient care.
More information on the HBI can be found at hbi.calgary.ca.