The arms and legs can exhibit alterations in their sensory reactions even though those regions have no reported symptoms, in response to a neck pain problem or a neck injury. If the area being tested exhibits an abnormally elevated pain response to a stimulus which would be typically painful anyhow this is termed hyperalgesia. Hyperalgesia may be caused by an increased response to incoming feelings within the local nerve systems in the neck. However, if the abnormalities of feeling are more extensive then the central nervous system is more likely to be processing abnormally. Whiplash patients may exhibit the more widespread symptoms.
Higher levels of neck pain and disability and more extensive pain when examined clinically are typical of patients with whiplash syndrome. Patients who suffer from whiplash associated disorder and from cervical nerve root lesions show similarities of abnormal sensory function which gives a clue that similar nerve mechanisms underlie both clinical syndromes. Allodynia may also occur, an abnormal pain reaction which again points towards central systems being involved in pain generation. If pain is reported by a patient when stimulated with a stimulus which would not normally be painful, this is termed allodynia.
At the time of the injury the abnormal pain processing mechanisms are set up in the nervous system and the same abnormalities have been shown to be present in patients with chronic whiplash pain. Whatever the severity of the whiplash injury, all sufferers seem to have some degree of pain overreaction to inputs, with this typically settling down in two or three months in less severe cases. Those patients who suffer from chronic neck symptoms and increased levels of pain will also likely have continuing mechanical overreaction which may persist rather than reduce with time. The levels of mental distress also affect pain thresholds.
It is clear that psychological distress is a feature of patients with whiplash syndrome, with more highly distressed patients having higher levels of pain and disability. However it does not appear that the increased pain sensitivity is caused by psychological distress but that the pain and the distress may be consequences of the heightened sensitivity in the central nervous system. Apart from these findings, investigations have also shown that patients can have an exaggerated pain reaction to cold and changes in the way the blood vessels constrict.
If a peripheral nerve is injured in the body then patients can develop the pain of cold overreaction and as this occurs in whiplash this may imply that some nerve injury is involved in both cases. A lesion of one of the cervical nerve roots can also cause the cold overreaction response and this again could link it to the same symptom presentation in whiplash. An overreaction to cold, cervical burning pain and sudden electric shock are all neuropathic pains, pains caused by abnormal responses in the nervous system, and have been identified in groups of patients with acute whiplash syndrome.
The jump from investigating the abnormalities in sensory abilities to the application of effective physiotherapy programmes is a large one. Physiotherapy or other manual therapy techniques can help to reduce hyperalgesia caused by local neck structure damage in the absence of other more severe abnormalities of the sensory systems. Prescribing an exercise routine can also have some effect in improvement of local coordination of muscles and reducing the tendency of nerves to overreact.
If someone has the extra features of neuropathic pain, the overreaction to cold, allodynia and more widespread sensitivity then treatment will have to be much more carefully planned. If the pain is stirred up by treatment this may increase the sensory abnormalities present and make the overall problem worse. More gentle manual and manipulative techniques may be more appropriate in these cases and physiotherapy has been shown to have some effectiveness in managing patients with whiplash.
The presence of the neuropathic symptoms such as overreacting to cold inputs means that there are typically much higher levels of disability and pain and the likelihood of physiotherapy being an effective management is uncertain. Medication for these pains is useful for about 30 percent of patients.
