I believe the correct answer is: problems coordinating his movements.
Concerning humans, the cerebellum (which is Latin term for "little brain") has an important role in motor control – movement-related functions are the most solidly established. Motor control displayed by cerebrum does not mean that he initiates movement, but contributes to coordination, precision, and accurate timing.
As Hunter was in a car accident and sustained damage to his cerebellum from a whiplash injury, the problem he would be most likely to experience after the accident is problems coordinating his movements.