Functional pain syndromes are believed to arise due to a state of central sensitisation or 'central sensitivity syndrome'
The clinical features experienced represent the endpoint of a complex interplay between genetic susceptibility, gene–environment interactions, and environmental triggers
Common syndromes include:
Fibromyalgia
Chronic fatigue syndrome (myalgic encephalitis)
Irritable bowel syndrome
Temporomandibular disorders
Chronic cardiac chest pain
A debilitating somatic functional pain syndrome
Epidemiology
Prevalence 2-7%
Mostly affects those 20-50yrs
Female preponderance (9x)
Key features
Pain >3 months' duration
Affects trunk and all four limbs
Tenderness over at least 11 of 18 defined trigger points
Sleep disturbance and marked fatigue
Rheumatoid arthritis co-exists in 25%
Pathophysiology
Pain predominates, but other features include fatigue, mood swings and cognitive impairment
Multiple theories but no clear aetiology/pathophysiology:
Dopamine or serotonin imparlance; COMT gene polymorphisms are associated with fibromyalgia
Dysfunction of inhibitory pathways
Best current evidence suggests an interplay of genetic and environmental risk factors leading to altered central pain perception
Management
Exclude other causes for symptoms such as anaemia (FBC), leukaemia (FBC), hypothyroidism (TFTs) and rheumatoid arthritis
Control of symptoms using a multidisciplinary, holistic, bio-psycho-social approach
Most patients will not get resolution of their symptoms and a pain management programme is vital
Conservative therapies
Patient education, support and motivation
Physiotherapy and regular exercise
Psychological therapies such as CBT
Pain management programmes
Pharmacological
Monotherapy with either TCA (amitriptylline) or SNRI (duloxetine)
They reduce pain and fatigue, while improving muscle stiffness, sleep and mood
Trigger-point injections with LA ± steroids provide only short-term benefit in the injected areas and are not recommended by NICE
Myalgic encephalomyelitis (ME)
Most common in females 20-40yo
Cause unclear – may be secondary to viral illness (eg EBV)
Pain in multiple sites associated with fatigue, poor sleep and sometimes mental health issues
Diagnosed following chronic fatigue >6 months with post-exertional malaise and MSK pain
Management is with:
Education, lifestyle, CBT and graded exercise
Generally no pharmacological therapy is indicated, although short drug trials may be used to address mood, pain or anxiety
A visceral functional pain syndrome
A poorly defined syndrome with no globally recognized clinical definition that represents a small element in the spectrum of cardiac chest pain
Generally described as anginal pain in the absence of:
Irregularities on angiogram
No bundle branch block on resting or exercise ECG
No evidence of cardiac comorbidities such as diabetes mellitus, valvular disease, or cardiomyopathy
May account for 10-15% of chest pain presentations to cardiology clinics
Management
MDT approach with cardiologists, cardiac surgeons, pain specialists, psychologists, and physiotherapists
Pain management programmes
Maintenance of medical therapies for cardiac ischaemia e.g. anti-platelets, β-blockers, statins, ACE-I