WWE Legend Jim Ross' Wife Died from Traumatic Brain Injury

WWE legend Jim Ross' wife, Jan Ross, suffered a traumatic brain injury ... the official cause of death after she was struck from behind by another car while riding her Vespa home.

The Oklahoma Office of the Chief Medical Examiner tells TMZ Sports that, while the cause of death has been determined, a toxicology report's still pending. Amy Elliott, the Chief Administrative Officer, also tells us the death has been ruled an accident.

Cops tell us the crash remains under investigation.

As we reported ... Jan suffered multiple skull fractures on March 20 after a 17-year-old male driving a 2000 Mercury Grand Marquis struck Jan's Vespa from behind. She was thrown off the scooter and both vehicles caught fire. Jan was not wearing a helmet.

She was being kept on life support but died 2 days later.