A Nevada City woman sustained major head injuries in an early-morning accident being called a “big mystery” by the California Highway Patrol. The CHP received a call of an injury accident on Highway 49 near North San Juan at about 12:30 a.m. Tuesday, said Officer Dina Hernandez. Officers responded and found a Nissan Pathfinder parked at a gas station south of Oak Tree Road. Nevada County Sheriff’s dispatch reports indicate that a man called 911 to report a woman in pain, with moaning heard in the background. He then called a second time and said he was asleep in the …