The basics - Fibromyalgia

Much can be done to alleviate the symptoms, says Dr Laurence Knott.

Although there are descriptions of the condition dating to the 17th century, fibromyalgia only achieved legitimacy in 1987 when it was recognised by the American Medical Association.

The term fibromyalgia is preferred to fibrositis, coined by Gower in 1904, because the latter term implies inflammation.

Pathophysiology
The pathophysiology of fibromyalgia is unknown. However, low serotonin levels, increased nerve growth levels and elevated levels of substance P (a neuropeptide in spinal fluid) all suggest an abnormal central processing of nociceptive pain input or central sensitisation.

Rehabilitation, physiotherapy and supervised exercise can improve physical symptoms

Epidemiology
Until proper diagnostic criteria were introduced, the incidence of fibromyalgia was not known with any accuracy. It is now estimated that between 0.5 and 5 per cent of the general population is affected.

Symptoms most commonly occur between the ages of 25 and 55, but can also occur in children, usually between 13 and 15 years. The female to male ratio is 7:1. There is a familial tendency, but no genetic link has been found.

Presentation
Diagnostic criteria were developed in 1990 and updated in 1992. Pain is the predominant presenting symptom and, to fit with a diagnosis of fibromyalgia, it must be widespread, on both right and left sides of the body, above and below the waist, and along the axial skeleton. The pain must be persistent, and have been present for at least three months.

Tiredness is characteristic of fibromyalgia, with 65 per cent of patients complaining of unrefreshing sleep, and 80 per cent experiencing morning fatigue. There appears to be a link between the condition and excessive caffeine and carbohydrate intake although more research is needed.

Other characteristics include morning stiffness or restless legs and swelling, numbness or tingling of the extremities.

Clinicians should be aware of the possible red flag symptoms, such as joint rather than muscle pain, or malaise, which may indicate a more sinister underlying pathology.

Comorbidities
Fibromyalgia is associated with a spectrum of other disorders. This is one of the reasons that doubt was cast upon the existence of fibromyalgia as an entity in its own right. It is classically associated with chronic fatigue syndrome, irritable bowel syndrome, migraine and dysmenorrhoea, to name a few.

In addition, many patients with fibromyalgia also suffer from depression. This may be the result of a combination of sleep deprivation, pain and loss of function.

Diagnosis
A general examination should be performed to rule out differential diagnoses (see top box). The differential diagnosis is wide and depends on presentation. Common conditions to exclude are myofascial pain syndrome and arthritis.

To fit with the diagnostic criteria there should be at least 11 out of 18 specific anatomical tender points. The forehead should be used as a control site. There are 18 specific points, with nine points on each side of the body (see middle box).

The pressure should be firm enough to cause the examiner's finger to blanch. The pain should be at the point of pressure and not referred elsewhere. The sensation should be felt as pain and not just tenderness.

There are no specific laboratory investigations in common use. FBC, ESR, LFTs, hepatitis C antibody, calcium and TFTs are commonly performed to rule out other diagnoses.

Imaging tends to be unhelpful, unless a specific differential diagnosis is in mind. It was hoped that antipolymer antibodies would prove to be a diagnostic test, but the evidence base to date suggests poor specificity for fibromyalgia.

Management
Fibromyalgia is not a life-threatening condition, nor is it progressive. However, if left untreated, chronic anxiety and pain can give the subjective impression of worsening symptoms over time.

The patient should be reassured that their symptoms are part of an increasingly recognised organic condition. While no cure has been found, much can be done to alleviate their symptoms.

Non-drug options include rehabilitation and physiotherapy. A Cochrane review has concluded that carefully supervised aerobic exercise can improve physical symptoms and mood, and reduce medication consumption.

Cognitive behavioural therapy, biofeedback and stress management may be helpful, but more research is needed.

There are contradictory comments in the literature about caffeine being helpful and harmful. Various dietary modifications are advocated from time to time but none has been subjected to rigorous large-scale trials.

Medication
The most successful medications appear to be those that are directed at the central pain sensitisation aspect. There is a growing body of evidence to support the use of tricyclic antidepressants and moderate evidence for the effectiveness of SSRIs and dual serotonin-norepinephrine reuptake inhibitors.

The antiepileptics pregabalin and gabapentin are also effective. The only analgesic demonstrated to be helpful is tramadol. NSAIDs and muscle relaxants may be beneficial, but the evidence base is less convincing.

Dr Knott is a GP in Enfield, London

COMMON DIFFERENTIAL DIAGNOSES

  • Cervical disc disease
  • Cervical myofascial pain
  • Cervical sprain and strain
  • Chronic pain syndrome
  • Complex regional pain syndromes
  • Hypothyroid myopathy
  • Lumbar degenerative disc disease
  • Lumbar facet arthropathy
  • Mechanical low back pain
  • Meralgia paresthetica
  • Myofascial pain
  • Osteoarthritis
  • Postpolio syndrome
  • Rheumatoid arthritis
  • Systemic lupus erythematosus

PRESSURE POINTS TO TEST FOR FIBROMYALGIA
Pain should be site specific

  • Occiput at the nuchal ridge
  • Trapezius
  • Supraspinatus
  • Gluteal
  • Low cervical
  • Second rib
  • Lateral epicondyle
  • Greater trochanter
  • Medial knee

Key points

  • Fibromyalgia is a recognised condition with specific diagnostic criteria.
  • The main pathophysiology appears to be an abnormal central processing of nociceptive pain input or central sensitisation.
  • The condition is non-progressive but symptoms can subjectively worsen over time.
  • Non-drug options include graded physiotherapy, rehabilitation and cognitive behaviour therapy.
  • Drug options include analgesia, antidepressants, anticonvulsants, NSAIDs and muscle relaxants.

References

  • Wolfe F, Smythe HA, Yunus MB et al. The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia. Report of the Multicenter Criteria Committee. Arthritis Rheum. 1990; 33: 160-72.
  • Mease P. Fibromyalgia syndrome: review of clinical presentation, pathogenesis, outcome measures, and treatment. J Rheumatol Suppl 2005; 75: 6-21.

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