Cervical Pain and Disability - Part Two
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.
Whiplash patients have generally higher levels of disability and pain and show more widespread pain on clinical examination. Patients with nerve root problems in the neck and those with whiplash associated disorder (WAD) both share features of sensory abnormality which may indicate that the underlying changes in the processing of pain are similar in both conditions. Another piece of evidence which may back up the role of central systems in these presentations is the occurrence of allodynia. Allodynia is the presence of pain in response to a normally non-painful stimulus such as touching, brushing or wearing clothes.
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.
Psychological distress is commonly present in patients who have whiplash associated disorder and if a patient has higher levels of pain and disability they are also likely to have elevated amounts of mental distress. The increased pain sensitivity that patients exhibit is not thought to be the result of psychological distress but the underlying pain reaction mechanisms in the central nervous system might be responsible for both the hyperalgesia and the psychological distress. Along with these findings, cold hyperalgesia (an increased pain reaction to cold) and abnormalities of circulatory function can occur.
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.
While the findings of sensory abnormalities in the neck are important it is hard to relate them realistically into effective physiotherapy. The local neck anatomy may be overreacting from its injury if there is hyperalgesia only locally to mechanical stimuli and this type of localised problem can be affected by manual therapies such as physiotherapy. Reducing this nerve over reactivity and improving muscle co-ordination and overall neck pain management may also be effected by exercise regimes.
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.