Chronic Pain Syndromes: Current Concepts and Treatment Strategies _ _______________________________
Treatment of Bone Pain with Calcitonin or Bisphosphonates
The cardinal features of fibromyalgia are widespread pain and tenderness in multiple regions of the body that are not attribut- able to another condition. In addition to pain and tenderness, patients with fibromyalgia often experience [321; 322]: • Morning stiffness • Tingling or numbness in the extremities • Headache that may include migraine • Irritable bowel syndrome • Sleep disturbances • Cognitive and memory dysfunction (referred to as “fibro fog”) • Dysmenorrhea • Restless legs syndrome Abnormal reactivity to sensory input is also characteristic of fibromyalgia. This includes [323]: • Hypersensitivity to painful stimuli applied to somatic structures, including painful and non- painful sites and normal control areas • Low pain thresholds to thermal, mechanical, electrical, and chemical stimuli • Pain increases with repeated stimulation (enhanced temporal summation) • Temperature sensitivity • Sensitivity to loud noises or bright lights Patients with fibromyalgia report either a gradual or a post- traumatic onset. Pain with fibromyalgia is described as a per- sistent, diffuse, deep, aching, throbbing sensation in muscles that is most often continuous [324; 325]. Other chronic pain syndromes can exist along with fibromyal- gia, including chronic fatigue syndrome, endometriosis, inflam- matory bowel diseases, interstitial cystitis, temporomandibular joint dysfunction, and vulvodynia. Whether these disorders share an underlying common pathologic basis with fibromy- algia is not known [322]. Rheumatic diseases such as rheumatoid arthritis, lupus, and ankylosing spondylitis are risk factors for fibromyalgia. A genetic contribution is suggested by an increased prevalence in patients with a positive family history of fibromyalgia [322]. PATHOPHYSIOLOGY Emerging evidence strongly suggests that disordered processing in central afferent neurons accounts for the dominant symp- toms of pain and tenderness in fibromyalgia [324; 326]. The contributory role of augmentation in pain signaling through central sensitization is supported by brain imaging findings consistent with abnormal pain response (e.g., decreased tha- lamic blood flow and accelerated brain gray matter loss) [325; 326]. Dysregulated autonomic, neuroendocrine, neurotrans- mitter, and neurosensory function and genetic predisposition have all been implicated in fibromyalgia pathophysiology ( Table 13 ) [324; 325].
Calcitonin is one of the few CRPS treatments validated by RCTs, and intranasal doses of 100–300 U per day are effica- cious for CRPS-related bone pain [311]. Despite the generally positive evidence for calcitonin efficacy, it is rarely prescribed and scarcely available [311]. Bisphosphonates may improve selected subtypes of CRPS, but given the occurrence of rare serious side effects, RCTs are required to confirm beneficial effects [311]. Topical Treatments A 5% lidocaine patch may have efficacy in some local or focal CRPS phenomena such as allodynia [311]. Dimethyl sulfoxide (50% cream for two months) has been found to significantly reduce pain compared with placebo [311]. Topical capsaicin is often found intolerably painful and unacceptable by patients with CRPS. Interventional Approaches Interventional approaches supported for use in patients with CRPS are placed in a three-level sequence. Inadequate or partial response should initiate a stepwise progression moving from less to more invasive, in conjunction with non- interventional therapies [311]. This approach consists of [311]: • Minimally invasive therapies
‒ Sympathetic nerve blocks ‒ IV regional nerve blocks ‒ Somatic nerve blocks
• More invasive therapies
‒ Epidural and plexus catheter blocks ‒ Neurostimulation ‒ Intrathecal drug infusion, such as baclofen • Surgical and experimental therapies ‒ Sympathectomy ‒ Motor cortex stimulation FIBROMYALGIA An estimated 10 million adults in the United States are afflicted with fibromyalgia, of whom 75% to 90% are female. However, the condition also occurs in men and children of all ethnic groups [320]. Diagnosis is usually made between the ages of 20 and 50 years, and with increasing age comes increased prevalence [320].
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