Members of the University of Calgary’s Cumming School of Medicine have identified the cause of a previously misunderstood post-seizure symptom that left patients feeling as if they had suffered a stroke.

In the minutes, hours or days following a seizure, some patients experience weakness or are rendered temporarily disabled, an anomaly known as Todd’s Paralysis.

“Many people with epilepsy who still experience seizures will have these postictal symptoms, these symptoms that occur after a seizure,” explained Dr. Cam Teskey of the University of Calgary’s Cumming School of Medicine, “but we haven’t known what causes these symptoms.”

“This research has determined that it’s this hypoperfusion hypoxia that is responsible for these symptoms.”

Studying data collected from both humans and rats, researchers determined the stroke-like symptoms were the result of decreased levels of oxygen in the brain post-seizure. In some cases, the oxygen level in the motor cortex of a rat’s brain plummeted to a level slightly above zero and remained there for more than an hour.

Using MRI scans, Dr. Paolo Frederico, an associate professor in the departments of clinical neurosciences and radiology, confirmed humans experience a similar drop,

“It was surprising to see it in humans,” said Dr. Frederico. “Actually more concerning than surprising that patients would be having significant reduction in blood flow following a seizure for up to one hour.”

Jordan Farrell, a PhD candidate in the neurosciences program, has worked on the research project for the last four years.

“Initially, when we found this, it was just fascinating. There are so many questions to ask about it.”

Teskey and Farrell determined the enzyme COX2 creates a byproduct during a seizure that constricts arteries resulting in a reduction in the flow of blood and oxygen. After identifying COX2’s role in Todd’s Paralysis, the researchers introduced a drug that inhibited the enzyme’s activation during a seizure and the animal subjects failed to experience stroke-like symptoms.

Two classes of drugs have proven successful in preventing Todd’s Paralysis in animals and the next step is a clinical trial involving humans.

According to the research team, the approval of the drug will likely take between three and five years. An estimated 140,000 Canadians have epilepsy.

With files from CTV’s Shaun Frenette