March 18, 2014
Sea Lions Found To Have A Type Of Epilepsy Similar To That In Humans
Lee Rannals for redOrbit.com - Your Universe Online
Scientists at Stanford University School of Medicine found a form of epilepsy in sea lions that is similar to one found in humans.
In a published paper in the Journal of Comparative Neurology, the team wrote that California sea lions exposed to a toxin in algae develop a form of epilepsy similar to a temporal lobe epilepsy.
Hundreds of sea lions wash up along the California coast each year suffering from seizures that have been caused by domoic acid -- a neurotoxin that produces memory loss, tremors, convulsions and death. This acid is produced by algae blooms that have been growing along the coastline in recent years.
Researchers studied the brains of sea lions that had been exposed to this toxin and they discovered a pattern of damage in the hippocampus.
"We found there was a loss of neurons in specific patterns that closely matched what is found in people," Paul Buckmaster, PhD, DVM, professor of comparative medicine at Stanford, said in a statement. "And there is synaptic reorganization — a rewiring of surviving neurons. This also matches what is found in humans with temporal lobe epilepsy."
Temporal lobe epilepsy is one of the most common forms of epilepsy in humans, and it typically begins with a seizure caused by an injury to the brain, such as head trauma. There is one documented case of a patient who was found to have developed this type of epilepsy after being exposed to domoic acid. The man, 84-years-old, suffered nausea, vomiting, coma and convulsions.
Buckmaster and colleagues retrieved samples of tissue from the hippocampus collected from 14 sea lions with epilepsy and compared them with similar samples from nine without epilepsy. They found that in most cases the hippocampus on only one side of the brain in the sea lions showed any signs of damage.
"That was really surprising," Buckmaster said. "That is what you find in people — 80 percent of the time the damage is just on one side."
In rats and mice, injury is seen in the hippocampus on both sides of the brain. The researchers speculated why there would be damage on only one side of the hippocampus. Buckmaster said this could be related to the size and structure of the brain, because a sea lion brain is 700 times larger than a mouse and 180 times larger than a rat brain.
He said sea lions could serve as good models for developing new treatments for the disease. Ultimately, scientists could use this research to develop a therapy that could be used early on to forestall brain damage and prevent further seizures.
"What we need is an interventional treatment — both in humans and sea lions," he said. "You'd give the treatment right after the brain injury, and that would prevent them from developing epilepsy. That's the dream, but we are not there yet."