Acute injury of the neck: anatomical and pathological basis of pain.

Headache, upper torso and upper limb pain can all originate in lesions of the cervical spine. The pain distribution is similar whether the cause is traumatic or degenerative. Nociceptive fibres are present in many cervical spine structures including the disc annulus, facet joint capsules, muscles, meninges, arteries, nerve roots and dorsal root ganglia. Such nerves are not present in the disc nucleus, facet articular cartilages and the ligamentum flavum. Central nervous connections between the trigeminal nucleus and upper cervical sensory input provide an explanation for some forms of headache and facial pain. This paper focuses on neck sprain from road traffic accidents as a cause of pain. Similar lesions are seen in the cervical spines of those who die immediately and survivors who die some years after a neck injury, from unrelated causes. Both discs and facet joints are injured. The common disc injury is a "rim lesion" or transverse tear near the anterior vertebral rim. It is caused by distraction and shearing in sudden extension. Both the posterior disc and the facets are compressed, causing disc contusion or herniation, facet haemarthroses, bruising around the C2 nerve, or fractures of articular processes. Suboccipital vascular congestion and annulus calcification are also seen in the "survivors". Chronic pain develops in 20-40% of the "survivors". The reasons include altered spinal mechanics, neural damage and vascular changes. Management must always start with an accurate diagnosis based on a history and physical examination. Simple investigations such as extension X-rays may reveal vacuum clefts in the same anatomical position as rim lesions. Nuclear scans detect increased uptake at damaged end plates or facet fractures.(ABSTRACT TRUNCATED AT 250 WORDS)