HIROSHIMA (Kyodo) -- 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 when explaining some of his nagging symptoms of whiplash at a lecture held in Hiroshima in September.

The condition has also affected his ability to calculate estimates in his carpentry job. After the accident, he began ordering the wrong quantities of supplies, he said.

And as his personality became increasingly aggressive, he lost two dear friends he had known for five decades.

"When will I get better? I want to work as a carpenter for another 10 years but..." Matsuda said, his voice trailing off. More than a year later, he continues undergoing treatment at the clinic.

In 2017, the defense team formed in Hiroshima as the first of its kind began assisting MTBI sufferers. They have been supporting lawsuits seeking damages from the perpetrators of accidents and providing consultation services to victims.

"Some patients are told that there is nothing wrong with them, even after visiting several hospitals, or their relationships with family and colleagues deteriorate due to their condition," said Kaori Hirata, the team's leader.

According to Hirata, many cases of higher brain dysfunction go unrecognized because the MRIs or CT scans show no clear signs of abnormalities, even if people experience trouble in their daily life after accidents.

In 2016, the transport ministry urged insurance companies to take appropriate measures for people whose scan results show no conclusive evidence of injury. However, the response from insurers has been underwhelming, while some patients have finally been granted permanent disability status after litigation.

In March, Udo, the medical society's chairman, and the legal team published a book introducing the mechanism of MTBI onset and the issues involved in helping patients, in an effort to make people aware of the illness.

Hirata is also doing her part in the fight for brain injury sufferers.

"We would like to continue our activities to make MTBI widely known and to help victims get relief," she said.

(By Kaori Shitamichi)