Sensory Abnormalities in Whiplash Injury
It is known that pain thresholds can be altered by the presence of anxiety or other psychological distress, and it is clear that psychological distress features in whiplash syndrome, with higher levels of pain and disability occurring in more highly distressed patients. Despite this it does not seem that this increased sensitivity to pain is directly caused by the distress but that the pain and the distress may be due to the pain experienced from the heightened sensitivity in the central nervous system.
Patients can also behave with an exaggerated pain reaction to cold and changes in the way their blood vessels constrict. This cold over-reaction is one of the typical symptoms of injury to the peripheral nerves of the body and so may suggest that nerve injury is present in some cases of whiplash injury. This overreaction to cold is also found in a nerve root injury to the neck, adding to the idea that the same underlying nerve difficulties are found in both this condition and whiplash.
In the examination of patients with recent whiplash injury a significant percentage showed what are called neuropathic pain symptoms. These are generated by the nervous system itself and include cold overreaction, burning neck pain and sudden bursts of electric shock pains. While the nature and frequency of these abnormal symptoms is well recorded in whiplash syndrome it is much harder to translate these into useful therapeutic approaches such as physiotherapy.
If the locally exaggerated pain reaction is in response to pain inputs from damaged structures and there are no other sensory abnormalities, the injured structures may be oversensitive due to the damage to the neck tissues. Injury to and irritable joints from injury can react favourably to physiotherapy or other manual therapies. Exercise may also reduce this type of increased nerve reactions and also improves the ways the muscles coordinate, improving the overall management of neck pain.
If the extra features of neuropathic pain, the overreaction to cold, allodynia and more widespread sensitivity are present then treatment should be much more carefully considered. If treatment stirs the pain up this may increase the abnormalities occurring and make the overall problem worse. More gentle manual and manipulative techniques may be more suitable in these cases and physiotherapy has been shown to have some effectiveness in managing patients with whiplash. The irritability, how easily the symptoms are stirred up, is the key point here.
Author: Jonathan Blood-Smyth