Whiplash Associated Disorder – Nervous System Changes
Once an injury occurs such as to the muscles and joints of the neck in whiplash injury, the inflammatory process from the damage excites the local nerves and makes them hypersensitive to incoming stimuli. Sleeping pain receptors (nerves that do nothing most of the time) are woken up and start sending barrages of pain signals towards the nervous system. Any unwise stress or movement on the damaged areas is rewarded by a severe volley of pain signals.
This continuous volley of pain input affects the nerves in the central nervous system which become sensitised by the pain inputs and begin themselves to amplify and pass on the pain towards the brain. This is known as central sensitisation and may be one of the reasons for ongoing pain. The whole pain pathway can become re-programmed right up to the sensory cortex of the brain, the whole path developing a heightened sensitivity to stresses and inputs.
While neurological mechanisms in the central nervous system are responsible for a degree of the pain, damaged neck structures are likely to exist and be continuing sources of pain. The facet joints in the neck have been shown to be regular pain sources in some patients with chronic whiplash. Pain may also be referred which is pain felt in an area away from the presumed region of damage or difficulty. The nervous system can interpret pain flowing from internal structures such as discs and facets as occurring in areas sharing close neurological links with them.
The three upper vertebral levels and their associated structures may refer pain to the head and the lower ones down to the first thoracic segment may refer pain into the arm. So the neck can refer pain to the head, the neck itself, the arms, the shoulders and the upper and mid thoracic spine. Patients suffering from whiplash may also respond abnormally to pressure, heat and cold also, the reasons for this not being clear, and hypersensitivity to cold which does not resolve quickly is a negative factor for developing long term pain problems.
A whiplash injury may set off complex changes in the way that the central nervous system processes incoming pain information, leading to abnormally high levels of reaction to what would normally be unremarkable stresses. However, these changes in the central processing may be maintained by pain inputs from the injured or altered discs, muscles, joints or ligaments, so physiotherapists need to target these structures with their treatments.
Author: Jonathan Blood-Smyth