“No one has committed suicide from being treated with oxygen,” Mr. Jones said.

Medical experts say that after a decade of intense focus, there is a heightened awareness of the consequences of concussions. The military has adopted new battlefield procedures to examine soldiers, new research is underway and schools are far more vigilant in making sure students are checked out after a head injury.

Experts say that the most effective treatment is addressing each of a patient’s symptoms individually, and in some ways, the search for new approaches has returned to the starting line. A concussion expert with the Mayo Clinic, Dr. David W. Dodick, said he believed a cheap nutritional supplement, N-acetylcysteine, could help treat concussion symptoms, and he hoped to study it.

It would not be the first time that the supplement, which is an antioxidant, has been tested for that use. In 2008, the Defense Department began a study of the supplement in soldiers in Iraq who had sustained a concussion. That trial showed benefits, but the study quickly became engulfed in controversy.

Dr. Dodick said that the dispute about the trial overshadowed a possible breakthrough and that N-acetylcysteine might be a valuable tool. “Every coach and parent could be carrying this on the sidelines,” he said.

Some researchers have also started trials of hyperbaric oxygen, and Dr. Harch is working on a trial he believes will provide compelling data about the treatment. Funding for the $1.2 million trial was originally allocated in 2008 as part of legislation backed by Louisiana’s congressional delegation, but the study was delayed.

An advertisement recruiting patients for the trial states, “If You Continue to Have Symptoms From a Mild Concussion You Experienced While Playing Sports, In a Car Accident, or During Military Service, You May Qualify.”

Dr. Harch has recruited more than 20 of the 50 patients he hopes to enroll. He is certain that the study will show breakthrough results.