IS FIBROMYALGIA A CENTRAL PAIN STATE?

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Is Fibromyalgia a Central Pain State?

Journal: J of Musculoskeletal Pain, Vol. 10, No. 1/2,2002, pp. 45-57

Author: Karl G. Henriksson, MD, PhD

Affiliation: Associate Professor, Department of Rehabilitation Medicine.

Pain Clinic and Neuromuscular Unit, Faculty of Health Sciences, Linköping

University, Sweden.

Address correspondence to: Karl G. Henriksson, MD, PhD, Neuromuscular Unit,

University Hospital, Linköping, S-58185 Sweden [E-mail address:

mailto:karl-g@... ].

SUMMARY.

Objective: To review the literature concerning pain mechanisms in

fibromyalgia [FMS].

Findings and Conclusions: Thirteen investigations using different methods,

comprising 250 patients with FMS, confirm a biological dysfunction of the

nociceptive system, especially in the central nervous system in the

majority of patients with FMS. The hyperexcitability in the nociceptive

nervous system may have different causes in the individual patient.

Localized long-standing muscle pain, chronic stress, genetic factors, and

hormonal changes may all play a role. Pain generators in the muscle may not

be specific for FMS but may be of importance for initiating and maintaining

pain and allodynia/hyperalgesia.

KEYWORDS. Fibromyalgia, pain mechanisms, muscular pain, central

sensitization

INTRODUCTION

According to the classification criteria proposed by the American College

of Rheumatology [ACR] fibromyalgia [FMS] comprises one symptom - chronic

multifocal pain - and one sign - generalized allodynia/hyperalgesia (]).

The patient who is diagnosed with FMS, however, is polysymptomatic. Besides

pain there is fatigue, sleep disturbance, psychological distress, impaired

muscle function, and symptoms that are usually regarded as stress-related.

Fibromyalgia is an illness, a syndrome, that effects three systems that

regulate our well being: the nociceptive system, the stress-regulating

system, and the immune system. These systems interact with each other,

making it difficult to determine which of them is primarily affected in an

individual patient. Psychological factors, personality traits, and social

circumstances play a role for the total clinical picture. Fibromyalgia is

indeed a biopsychosocial syndrome. The biological part concerns mainly pain

and allodynia/hyperalgesia as well as biological changes related to

continuous physical and emotional stress. This article will deal only with

pain and allodynia. Allodynia is pain elicited by normally nonpainful

stimuli. Hyperalgesia is increased pain intensity and prolonged pain

duration evoked by stimuli that normally are painful.

[ ... ]

CONCLUDING REMARKS

There is strong support for the notion that pain and allodynia/hyperalgesia

in FMS have an organic cause. The hyperexcitability in the nociceptive

nervous system is mainly due to changes in the CNS. Longstanding excitation

of nociceptors and low threshold mechano-receptors in the muscle may

initiate and maintain such hyperexcitability. The permanent changes

constitute a disease. There are methods for objectively diagnosing this

disease.

The psychological and social consequences of chronic pain in FMS are the

main determinants for the degree of disability and handicap.

Many causes could initiate and maintain the disease: e.g.,longstanding

local or regional musculoskeletal pain, changes in stress-regulating

systems, hormonal changes, changes in serotonin metabolisms, and genetic

factors.

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