Last March, Satoshi Matsuda's car was rear-ended while he sat inside waiting at a traffic light. Immediately afterward, he recalled feelings of dizziness and nausea. After the accident, the man, a 65-year-old carpenter from Hiroshima in western Japan, began confusing his job orders and became increasingly irritable about everything.

He has ended relationships with longtime friends due to his persistent health condition. Matsuda (not his real name) is one of some 1.35 million people in Japan who suffer from mild traumatic brain injury or MTBI, most commonly manifesting as concussion.

Symptoms include memory loss, dizziness, sensory sensitivity, difficulty with thinking, and mood swings, among others. Many of the patients typically experience whiplash in car accidents or from sports injuries, resulting in the symptoms of higher brain dysfunction without proper treatment or compensation since their injuries are too small to detect in MRIs and CT scans. But a legal defense team formed in Hiroshima by volunteer lawyers and local specialists is now raising awareness about the problem in order to help patients struggling with the illness.

According to Hiroshi Udo, director of the Yuwa Clinic in Hiroshima and chairman of the Japanese Society for New Meridian Medicine, MTBI occurs when nerve fibers in the brain are damaged due to head impacts from rear-end collisions and other external injuries. "I couldn't get across the crosswalk because the road lines appeared raised," said Matsuda.