Is FMS a Central Pain State?

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" Is Fibromyalgia a Central Pain State? "

Source: Journal: J of Musculoskeletal Pain, Vol. 10, No. 1/2,2002

by Karl G. Henriksson, MD, PhD

Affiliation: Associate Professor, Department of Rehabilitation

Medicine. Pain Clinic and Neuromuscular Unit, Faculty of Health

Sciences, Linköping University, Sweden. E-mail address: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 playa 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.