This could not be psychologically mediated. Thus, it is a proof of structural injury if the patient's history is reliable. If this kind of symtoms starts an hour or more after impact, spinal cord injury is not impossible, but muscular tension is a more probable explanation. If this disturbance is obvious already the first few days after the accident, the connection is more probable than should it occur only after weeks or months. As micturition is controlled by the brain, a spinal cord injury could disturb the mechanism.
Chronic pain is known either to make discharge difficult or to cause frequent discharges.
A neuro-urological investigation could shed light over this matter and discriminate the few cases of established spinal cord injury. Since the trauma is located to the neck, one does not expect symtoms from the lower part of the body unless nerve fiber tracts from the brain to the lumbar spinal cord have been hurt. Therefore, pain in the legs and impaired sensation should arouse suspicion of neurotrauma. Just as well, muscular tension, disseminating from the neck to the lumbar region, could explain minor compression of nerve structures beside the spine causing exactly the same sensory symtoms. Still, at least I think that this problem mostly originates from muscular tension in the face with light pressure to small branches of the trigeminal nerv, the sensory nerve of the face.