Sciatica is back pain that shoots down the leg from compression of the sciatic nerve in the back. Yes sciatica can be caused by a car accident. To blame the accident the leg pain should start during or just after the car accident. It is difficult to determine the cause and timing of a disk herniation on MRI. The disk herniation may have been present prior to the MRI or herniated at the time of the accident, but without a MRI prior to the accident it is difficult to say when it herniated. Either way, if the pain started at the accident then the sciatica was caused by the accident and the disk is new or been aggravated by the accident (this is called an aggravation of pre-existing condition). Good Luck!