New York ? Researchers are reporting the first treatment to speed recovery from severe brain injuries caused by falls and car crashes: a cheap flu medicine whose side benefits were discovered by accident decades ago.

Severely injured patients who were given amantadine got better faster than those who received a dummy medicine. After four weeks, more people in the flu drug group could give reliable yes-and-no answers, follow commands or use a spoon or hairbrush — things that few of them could do at the start. Far fewer patients who got amantadine remained in a vegetative state, 17 percent versus 32 percent.

“This drug moved the needle in terms of speeding patient recovery, and that’s not been shown before,” said neuropsychologist Joseph Giacino of Boston’s Spaulding Rehabilitation Hospital, co-leader of the study. He added: “It really does provide hope for a population that is viewed in many places as hopeless.”

Many doctors began using amantadine for brain injuries years ago, but until now there’s never been a big study to show that it works. The results of the federally funded study appear in today’s New England Journal of Medicine.

Each year, an estimated 1.7 million Americans suffer a traumatic brain injury. Falls, car crashes, colliding with or getting hit by an object, and assaults are the leading causes.