The patient’s seizures were getting more severe and increasingly frequent. One or two per month grew to several each week. Each burst of uncontrolled electrical activity sent shock waves through his injured brain, causing tremors and confusion. Unable to eat, his body weight dropped by nearly one-third in a few months. His health was deteriorating fast.
In October 2020, the patient—a seven-year-old sea lion named Cronutt—underwent an experimental brain surgery that involved transplanting healthy pig neurons into his damaged hippocampus. Now, more than a year since the treatment, Cronutt is seizure-free, says Scott Baraban, a neuroscientist at the University of California, San Francisco, who led the effort.