Introduction

Chronic pain syndrome tends to be very difficult to manage because of its complex natural history, unclear aetiology and poor response to therapy. There is no clear definition but it is characterised by pain which persists despite adequate time for healing. The minimum duration of pain varies between 3 and 6 months. Some argue that any pain that persists longer than the reasonable expected healing time for the involved tissues should be considered as chronic pain. The impact of chronic pain on patients' lives varies from minor restrictions to complete loss of independence.¹

Pathophysiology¹

This is poorly understood. It may be a learned behavioural syndrome beginning with a stimulus causing pain. Pain behaviour is then rewarded externally (e.g. attention from family, friends, health professionals, medication, compensation, time off work) or internal factors (e.g. relief from guilt, sexual demands, responsibilities). Eventually, pain behaviour occurs without any stimulus. Virtually any systemic condition that causes pain can thus be implicated in the aetiology of chronic pain syndrome.

It should be emphasised that the pain is very real and is experienced as discomfort by the patient in the same way as any other pain. A learned behavioural syndrome operates on an entirely unconscious level and does not involve deliberate or conscious input from the patient. These patients do not choose to be in pain, no matter what the 'pay-off' in terms of psychosocial or personal benefit. They should therefore be accorded the same attention and care as patients suffering from any other painful condition.

Epidemiology

A systematic search of multiple databases found a 1-month prevalence of moderate-to-severe non-cancer chronic pain in Europe of 19%.² The condition is more common in women.¹ One study found that short education, poor self-rated health, high body mass index and physical strain at work were predictors of chronic pain.³

Presentation¹

The presentation can be multifarious and involve any system but the common factor is poor response to pain control despite adequate therapy.

Sternbach's 6 D 's of chronic pain syndrome are as follows:

• Dramatisation of complaints
• Drug and/or alcohol misuse
• Dysfunction
• Dependency
• Depression
• Disability

The history should include the usual questions one would ask any patient presenting with pain - e.g. type, duration, location, radiation and aggravating or relieving factors.

A psychosocial history is particularly important. Sufficient information should be obtained to evaluate:

• Depression.
• Anxiety disorder.
• Somatisation.
• Physical or sexual abuse.
• Recreational drug and alcohol abuse.
• Family, marital or sexual problems.

Appropriate systematic examination should be made, depending on the presenting symptoms, to exclude organic disease.There will be no relevant signs indicating the cause of pain, e.g. no joint swelling, muscle weakness, weight loss or fever. The disability is usually out of proportion to the impairment and the objective findings. Waddell's signs may be positive (these are tests to assist the identification of nonorganic conditions).⁴

Associated diseases¹

• Major depression
• Somatisation disorder
• Hypochondriasis
• Conversion disorder

Differential diagnosis

Causes of diffuse musculoskeletal pain, including:

• Rheumatoid arthritis.
• Spondyloarthropathy, e.g. ankylosing spondylitis, Reiter's syndrome.
• Vasculitis.
• Polymyositis, dermatomyositis.
• Polymyalgia rheumatica.
• Toxin related, e.g. eosinophilia-myalgia syndrome, silicone implants.
• Osteomalacia.
• Chronic fatigue syndrome.
• Fibromyalgia.
• Complex regional pain syndrome.
• Hyperthyroidism.
• Hypothyroidism.
• Neoplasm.
• Multiple sclerosis.
• Entrapment neuropathy.

Investigations¹

The diagnosis is by exclusion of other specific causes of chronic pain. Although it is essential to rule out any underlying aetiology for the pain, a great deal of care and skill is often required to avoid unnecessary and inappropriate investigations and referrals, which only serve to increase the underlying anxiety of the patient and their family. A balance must be struck between ensuring that important conditions are excluded whilst avoiding an endless quest for a non-existent diagnosis.

Management¹

There are no proven, comprehensive treatments in primary care for patients with medically unexplained symptoms.⁵ Management must be tailored for each individual patient.⁶ The treatment should be not just aimed at pain relief but also aimed at changing pain behaviour and improving function. The goals of treatment must be realistic and should be focused on restoration of normal function (minimal disability), better quality of life, reduction of use of medication and prevention of relapse of chronic symptoms:⁷

• Relaxation methods, patient education.⁶
• Antidepressants: both tricyclics and selective serotonin reuptake inhibitors (SSRIs) have been shown to be effective.
• Tizanidine, which inhibits central nervous system activity, may be helpful. Normally used for spasticity associated with multiple sclerosis or spinal cord injury or disease, its use for this indication is off licence and the necessary consent should be obtained from the patient.
• Simple and compound analgesics, non-steroidal anti-inflammatory drugs: long-term and excessive use of all symptomatic analgesics should be avoided because of the risk of dependence and abuse. One study found that the odds of recovery from chronic pain were almost four times higher among individuals not using opioids compared with individuals using opioids.⁸
• Transcutaneous electrical nerve stimulation (TENS) machine.
• Physiotherapy and occupational therapy have an important role in functional restoration for patients. Recreational therapy can help the patient with chronic pain take part in pleasurable activities that help decrease pain.
• Psychotherapy: behavioural and cognitive psychotherapies.⁹
• Vocational therapy.
• Nerve blocks and other spinal interventions, e.g. epidural injections for chronic back pain.¹⁰
• Sympathetic blocks are more effective therapeutic tools for chronic pain.

Complications

• Prolonged physical suffering.
• Sleep disturbance.
• Marital or family problems.
• Loss of employment.
• Disability.
• Adverse medical reactions from long-term therapy.

Prognosis

• The prognosis is variable but often poor.
• However, considerable improvement is possible with suitable support and management.

Document references

1. Singh MK et al; Chronic Pain Syndrome, Medscape, May 2010
2. Reid KJ, Harker J, Bala MM, et al; Epidemiology of chronic non-cancer pain in Europe: narrative review of Curr Med Res Opin. 2011 Feb;27(2):449-62. Epub 2011 Jan 3. [abstract]
3. Sjogren P, Gronbaek M, Peuckmann V, et al; A population-based cohort study on chronic pain: the role of opioids. Clin J Pain. 2010 Nov-Dec;26(9):763-9. [abstract]
4. Painter F; The Use Of Waddell Tests In Workers Compensation Claims chiro.org 2003
5. Smith RC, Lein C, Collins C, et al; Treating patients with medically unexplained symptoms in primary care. J Gen Intern Med. 2003 Jun;18(6):478-89. [abstract]
6. Chen YL, Francis AJ; Relaxation and imagery for chronic, nonmalignant pain: effects on pain symptoms, Pain Manag Nurs. 2010 Sep;11(3):159-68. Epub 2009 Sep 8. [abstract]
7. Muller-Schwefe G, Jaksch W, Morlion B, et al; Make a CHANGE: optimising communication and pain management decisions. Curr Med Res Opin. 2011 Feb;27(2):481-8. Epub 2011 Jan 3. [abstract]
8. Breivik H, Collett B, Ventafridda V, et al; Survey of chronic pain in Europe: prevalence, impact on daily life, and treatment. Eur J Pain. 2006 May;10(4):287-333. Epub 2005 Aug 10. [abstract]
9. Jackson JL, O'Malley PG, Kroenke K; Antidepressants and cognitive-behavioral therapy for symptom syndromes. CNS Spectr. 2006 Mar;11(3):212-22. [abstract]
10. Boswell MV, Shah RV, Everett CR, et al; Interventional techniques in the management of chronic spinal pain: evidence-based practice guidelines. Pain Physician. 2005 Jan;8(1):1-47. [abstract]

Internet and further reading

• Bandolier, The Oxford Pain Internet Site

Acknowledgements