Chronic Neck Pain
Chronic neck pain is defined when neck pain has persisted for more than three months. Around 20-40% of patients with acute neck pain continue on to have chronic neck pain.
Aetiology
- See also: Causes and Sources of Neck Pain
Idiopathic Neck Pain
Idiopathic neck pain refers to neck pain that arose insidiously, i.e. in the absence of a specific inciting event or other explanation. Anatomically the muscles, discs, and joints of the cervical spine are all possible nociceptive generators, however there there is a lack of research into the pathophysiology of how pain might arise from these structures
Muscles: Muscle sprain as a cause of neck pain fits better in the acute setting rather than the chronic setting, as muscle injuries heal quickly. Muscle pain has been hypothesised to be a cause of chronic pain using terms such as muscle spasm, chronic muscle ischaemia, and trigger points. However there is no agreed method of diagnosis.
In chronic neck pain there is often muscle dysfunction. There is reduced activity of the deep cervical flexor muscles (longus cervicis and capitis), increased activity of the superficial flexors (sternocleidomastoid), and increased activity of the accessory neck muscles (anterior scalenes and trapezius). The reasons for this pattern is unclear but it is likely a secondary phenomenon, rather than the primary cause of pain.
Intervertebral Discs: With age there is disc dehydration and osteophytosis, however this has not been shown to be linked to pain. Without trauma, it is not clear why a disc should become painful, or if indeed it does at all.
Synovial Joints: The most likely source of nociception in chronic idiopathic neck are the synovial joints of the neck. These are the facet joints, atlanto-axial joints, and atlanto-occipital joints. However, imaging findings of osteoarthritis of the synovial joints don't correlate with pain, and so diagnosis is made with diagnostic local anaesthetic injections.
Post-traumatic Neck Pain
- Main article: Chronic Post-Traumatic Neck Pain
The aetiology of chronic pain is clearer in the setting of whiplash and trauma in general.
Muscles: Muscles are unlikely to be implicated as a primary cause of persistent cervical pain following trauma.
Intervertebral Discs: The anterior annulus fibrosis can be torn or avulsed from the vertebral body in extension injuries. These injuries are likely to be painful, but may only be apparent in vivo rather than on imaging.
Synovial Joints: The zygapophyseal joints and lateral atlanto-axial joints are susceptible to extension injuries. Injuries include meniscoid contusions, intra-articular haemorrhage, capsular tear, annulus tear, subchondral articular fractures, and articular pillar fractures. These injuries are likely to be painful, but again are often not apparent on imaging.
Alar and Transverse Ligaments: Severe trauma can result in rupture of the suboccipital ligaments. The main clinical features are instability of the axis or spinal cord injury. In less severe trauma, there is radiological evidence that the alar and transverse ligaments can be injured in whiplash. Injury to the alar ligaments was more common than the transverse ligaments. Also alar ligament injury wasn't found in controls, while transverse ligament injury was found in controls. It isn't clear whether injury to these ligaments can result in chronic neck pain or, because they are at C1, cervicogenic headache.
Psychological Factors
There is no evidence to support the view that chronic neck pain, whether post-traumatic or not, is secondary to somatization, conversion disorder, malingering, hypochondriasis, or due to secondary gain. A psychosocial label is not falsifiable, i.e. it cannot be refuted, and so it a belief rather than a valid diagnosis. For many patients a biomedical diagnosis cannot be made, but the Musculoskeletal Medicine view is generally that this is due to the infancy of research in this area, rather than the primary cause being nebulous psychosocial factors.
Clinical Features
- Significant trauma (eg. fall in osteoporotic patient, motor vehicle accident)
- Infective: (eg. fever, meningism, immunosuppression, intravenous drug use, exotic exposure, recent overseas travel)
- Constitutional: (eg. fevers, weight loss, anorexia, past or current history of malignancy)
- Iatrogenic: Recent surgery, catheterisation, venipuncture, manipulation
- Neurological: Symptoms/signs especially of upper motor neuron pathology, vomiting
- Genitourinary/Reproductive: UTI, haematuria, retention, uterine, breast
- Endocrine: Corticosteroids, diabetes, hyperparathyroid
- Gastrointestinal: Dysphagia
- Integumentary: Infections, rashes
- Cardiorespiratory: Cough, haemoptysis, chest pain, shortness of breath, diaphoresis, ripping/tearing sensation (dissection), CVD risk factors, anticoagulants
- Rheumatological: History of rheumatoid arthritis (atlanto-axial disruption)
- Awkward posture (atlantoaxial rotatory subluxation in children)
Imaging
In general there is no link between cervical degenerative joint disease and pain. However, there is a slight clinical significance with degenerative disc (but not facet osteoarthritis) findings at the C5/6 level. There is also an association with marked (level 3) degenerative changes and neck pain.
Recently radiologists and surgeons are frequently using CT scintigraphy. This modality has 'concept validity.' It can detect small occult fractures and tumours. However it shows increased blood flow, not pain. It tends to miss cases where the pain is arising from soft tissue damage, for example capsule tears.
References
- Bogduk, Nikolai, and Brian McGuirk. Management of acute and chronic neck pain : an evidence-based approach. Edinburgh New York: Elsevier, 2006.
