WIFE WAS DRIVING IN A RESIDENTIAL AREA GOING APROX15MPH. DID NOT HIT ANYTHING ORWAS NOT STRUCK BY ANYTHING. WAS STRUCK IN THE HEAD THROWING HER HEAD VIOLENTLY FORWARD, BY THE DRIVERS SIDE HEADREST DEPLOYING. SHE WAS SHOCKED AS SHE HAD NO IDEA WHAT HAD HAPPENED. SHE IMMEDIATELY FELT PAIN AND LIGHT HEADEDNESS. RETURNED HOME LESS THAN BLOCK FROM THE HEADREST DEPLOYING. I TOOK HER TO ER, AFTER 2 HRS DETERMINED SHE HAD A CONCUSSION AND STRAINED MUSCLES IN HER NECK, BASICALLY WHIPLASH.