Evidence-Based Reviews

Fibromyalgia: Psychiatric drugs target CNS-linked symptoms

Current Psychiatry. 2009 March;8(3):37-50

Repeated pain signals in the periphery may sensitize spinal cord neurons, resulting in amplified and prolonged signals traveling to the brain

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References

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Comment on this article

Patients with fibromyalgia are a heterogeneous group, yet many describe a common experience: seeing multiple physicians who seem unable or unwilling to provide a diagnosis or treat their symptoms. This situation may be changing with the recent FDA approval of an anticonvulsant and 2 antidepressants for managing fibromyalgia symptoms.

These medications—pregabalin, duloxetine, and milnacipran—reflect a revised understanding of fibromyalgia as a CNS condition, rather than an inflammatory process in the muscles or connective tissue. As a result, psychiatrists—because of our experience with CNS phenomena and managing antidepressant and anticonvulsant medications—are likely to play a larger role in treating fibromyalgia.

CASE REPORT: ‘Just too tired’

Ms. D, age 50, has a history of migraine headaches and is referred by her primary physician for evaluation of depression and anxiety. She reports deteriorating mood over 6 months, beginning when a minor car accident left her “very sore the next day.”

Clinical Point

Musculoskeletal pain is not the most problematic symptom for many patients with fibromyalgia

“Nothing helps” the persistent pain in her back, shoulders, and thighs, which she rates as 7 to 8 on a 0-to-10 pain scale. She describes an intense ache, “like having the flu,” that worsens with activity and in stressful situations. She also experiences nausea and intermittent diarrhea, debilitating fatigue, and sleep disturbance.

Ms. D reports she is depressed because she feels “just too tired” after work to keep up with social activities or housework. Her physician’s referral notes a normal physical exam except for tenderness over her upper back and hips. Laboratory testing is negative.

Making the diagnosis

American College of Rheumatology (ACR) criteria for fibromyalgia require widespread pain for at least 3 months. “Widespread” is defined as pain in the axial skeleton, left and right sides of the body, and above and below the waist. Pain must be found in at least 11 of 18 tender point sites on digital palpation using a force of approximately 4 kg/cm².¹ For many fibromyalgia patients, however, musculoskeletal pain is not their most problematic symptom (Table 1). They may suffer:

migraine and tension headaches (10% to 80% of patients)
irritable bowel syndrome (32% to 80%)²
mood disorders (major depressive disorder [62%], bipolar disorder [11%])
anxiety disorders (panic disorder [29%], posttraumatic stress disorder [21%], social phobia [19%]).³

Clinical Point

Fibromyalgia patients show lower levels of serotonin, norepinephrine, and dopamine metabolites in cerebrospinal fluid

ACR criteria are useful in research but lack many common symptoms and comorbidities. A structured interview that follows the DSM-IV-TR format incorporates other symptoms into the diagnosis (Table 2).⁴

Because patients with fibromyalgia often meet criteria for somatization or somatoform disorders, how to classify them—as medically or psychiatrically ill—is controversial. Some patients believe their mood or anxiety problem stems from the difficulty they experience dealing with their physical symptoms, and if they could feel better physically they would not be depressed or anxious. Others believe their psychiatric symptoms impede their ability to help themselves feel better.

Consider fibromyalgia in any patient with widespread pain of unknown cause. Before making the diagnosis, rule out other illnesses that present with similar symptoms (Table 3). Because many patients newly diagnosed with fibromyalgia worry that something “more serious” may be going on, confirm the diagnosis with appropriate testing and physical examination, usually by a rheumatologist or primary care physician.

Table 1

Medical and cognitive symptoms related to fibromyalgia

Neurologic Tension/migraine headache
Psychiatric Memory and cognitive difficulties Mood disturbance Anxiety disorders
Ear, nose, throat Sicca symptoms Vasomotor rhinitis Vestibular complaints
Cardiovascular Neurally mediated hypotension Mitral valve prolapse Noncardiac chest pain
Gastrointestinal Esophageal dysmotility Irritable bowel syndrome
Urological Interstitial cystitis
Gynecological Vulvodynia Chronic pelvic pain
Oral/dental Temporomandibular joint syndrome
Other (general) Chronic fatigue syndrome Sleep disturbances Idiopathic low back pain Multiple chemical sensitivity

Table 2

Fibromyalgia: Structured interview for diagnosis

A. Generalized pain affecting the axial, plus upper and lower segments, plus left and rights sides of the body
Either B or C:
B. At least 11 of 18 reproducible tender points
C. At least 4 of the following symptoms: Generalized fatigue Headaches Sleep disturbance Neuropsychiatric complaints Numbness, tingling sensations Irritable bowel symptoms
D. It cannot be established that disturbance was due to another systematic condition
Source: Reference 4

Table 3

Differentiating fibromyalgia from illnesses with similar symptoms

Illness	Tests to differentiate from primary fibromyalgia
Rheumatic diseases Osteoarthritis Spondyloarthropathies, rheumatoid arthritis Systemic lupus erythematosus, polymyalgia rheumatica Osteomalacia Myopathy	Radiographs Rheumatic markers (antinuclear antibody, rheumatoid factor, antibodies) Inflammatory markers (ESR, C-reactive protein) Vitamin D level CPK
Neurologic Multiple sclerosis, Chiari’s malformation, spinal stenosis, radiculopathy Neuropathy	MRI EMG
Endocrine Hypothyroidism Diabetes	TSH Basic chemistry panel with fasting glucose
Other Infectious Lyme disease Hepatitis Anemia Cancers	CBC Lyme titer Hepatitis antibody panel, liver function tests Hemoglobin/hematocrit Routine cancer screening tests, bone scan, blood chemistries specific for suspected primary cancer
ESR: erythrocyte sedimentation rate; CPK: creatine phosphokinase; EMG: electromyography; TSH: thyroid-stimulating hormone; CBC: complete blood count