SECTION D: Pain Associated with Medical Illness

Fibromyalgia

INTRODUCTION

Understanding of fibromyalgia syndrome (FMS) has evolved over the past 20 years. Once thought to be related to muscular pain and inflammation, it is now more widely understood to be a largely noninflammatory, soft-tissue pain condition, best separated from the entity of myofascial pain, with which it has traditionally been grouped. FMS also has strong associations with other diseases that are deemed central sensitivity syndromes, suggesting that central sensitization plays an important role in the chronic nature of fibromyalgia.¹ Because of the complexity of the disorder, a multimodal approach has the most success in effectively treating the physical, psychological, and emotional aspects of FMS.

CLINICAL FEATURES

DIAGNOSIS

The hallmarks of FMS are widespread pain, fatigue, sleep disturbances, and cognitive changes, as well as psychological distress. Patients often complain of pain “all over my body.” They often report chronic insomnia, either having trouble falling asleep or waking up frequently in the night, leaving them exhausted and stiff in the daytime. They also complain about difficulty with cognition and concentration; the phenomenon of “fibro fog” is frequently mentioned in patient forums and websites. Additionally, patients experience depression; in one study, as many as 40% of patients with FMS were diagnosed with depression at the same time as their FMS was diagnosed.² Many features of FMS overlap with other diseases, and, indeed, FMS is often seen in conjunction with other diseases that lack structural pathology, including irritable bowel syndrome (IBS), interstitial cystitis, temporomandibular disorder, tension headache and migraine, chronic fatigue syndrome, posttraumatic stress disorder, and vulvodynia. These disease states all share a common feature of central sensitization and have been named central sensitivity syndromes to denote this.¹ Any patient with this broad spectrum of symptoms should be evaluated for FMS.

The diagnosis of FMS is criteria-based rather than a diagnosis of exclusion.² The American College of Rheumatology (ACR) developed criteria for FMS research that have been used clinically to diagnose FMS since their publication in 1990.³ The diagnosis depends on the presence of generalized pain in three or more sites, as well as the physical examination finding of tenderness in at least 11 of 18 defined anatomic locations (Table 59-1 and Fig. 59-1). Patients with FMS have pain with 4 kg of digital pressure; this can be estimated by pressing the examining thumb against the spot in question with enough pressure to blanch the thumbnail about halfway down the nail bed.²