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Novel Brain Surgery Seeks to Reverse Epilepsy in Sea Lion

VALLEJO, Calif. — The adolescent patient turned sullen and withdrawn. He hadn’t eaten in 13 days. Treatment with steroids, phenobarbital and Valium failed to curb the symptoms of his epilepsy. Then, on Sept. 18, he had a terrible seizure — violently jerking his flippers and turning unconscious in the water.

Cronutt, a 7-year-old sea lion, had to be rescued so he didn’t drown. His veterinarian and the caretakers at Six Flags Discovery Kingdom began discussing whether it was time for palliative care.

“We’d tried everything,” said Dr. Claire Simeone, Cronutt’s longtime vet. “We needed more extreme measures.”

On Tuesday morning, Cronutt underwent groundbreaking brain surgery aimed at reversing the epilepsy.

If successful, the treatment could save increasing numbers of sea lions and sea otters from succumbing to a new plague of epilepsy. The cause is climate change.

As oceans warm, algae blooms have become more widespread, creating toxins that get ingested by sardines and anchovies, which in turn get ingested by sea lions, causing damage to the brain that results in epilepsy. Sea otters also face risk when they consume toxin-laden shellfish.

The animals who get stranded on land have been given supportive care, but often die. Cronutt may change that.

“If this works, it’s going to be big,” said Mariana Casalia, a neuroscientist at the University of California, San Francisco, who helped pioneer the techniques that led to a procedure that took place a vet surgery center in Redwood City, Ca.

That procedure was done by three neurosurgeons at U.C.S.F., who ordinarily operate on humans. During the operation, they bored a small hole in Cronutt’s skull, inserted an ultrathin needle into the hippocampus of the sea lion’s brain, then implanted embryonic brain cells extracted from a 35-day-old pig. These so-called “inhibitory cells” tamp down the electrical activity in the brain that leads to seizures, a process identified by Scott Baraban, a professor of neurosurgery who runs the lab where Dr. Casalia works. Over a decade, their technique has proved effective in curing epilepsy in mice.

Credit…Claire Simeone

Cronutt, the first higher mammal to get the treatment, emerged from the surgery and anesthesia midday and was breathing on his own, a first step. Whether the surgery successfully reverses his condition won’t be known for several weeks.

Pig cells are important because they have properties of higher mammal species, including the sea mammals succumbing to epilepsy. And sea lions and sea otters are increasingly at risk for the disease.

The widely documented phenomenon, first discovered in 1998, led to a surge in beaching of sea lions in 2002, another in 2015, and annual summer beachings. By now, thousands of sea lions have been poisoned by the toxin, called domoic acid. It depletes inhibitory cells that ordinarily help offset excitatory cells in the brain’s electrical system. When those cells get out of balance, seizures