The first thing Debra McVean did when she woke up at the hospital in March 2024 was try to get to the bathroom. But her left arm wouldn’t move; neither would her left leg. She was paralyzed all along her left side.

She had suffered a stroke, her doctor soon explained. A few nights before, a blood clot had lodged in an artery in her neck, choking off oxygen to her brain cells. Now an M.R.I. showed a dark spot in her brain, an eerie absence directly behind her right eye. What that meant for her prognosis, however, the doctor couldn’t say.

“Something’s missing there, but you don’t know what,” Ms. McVean’s husband, Ian, recalled recently. “And you don’t know how that will affect her recovery. It’s that uncertainty, it eats away at you.”

With a brain injury, unlike a broken bone, there is no clear road to recovery. Nor are there medical tools or therapies to help guide the brain toward healing. All doctors can do is encourage patients to work hard in rehab, and hope.

That is why, for decades, the medical attitude toward survivors of brain injury has been largely one of neurological “nihilism,” said Dr. Fernando Testai, a neurologist at the University of Illinois, Chicago, and the editor in chief of the Journal of Stroke and Cerebrovascular Diseases. Stroke, he said, “was often seen as a disease of ‘diagnose and adios.’”

That may be about to change. A few days after Ms. McVean woke up in the Foothills Medical Center in Calgary, she was told about a clinical trial for a pill that could help the brain recover from a stroke or traumatic injury, called Maraviroc. Given her level of physical disability, she was a good candidate for the study.