April 30, 2003 -- People who suffer from fibromyalgia appear to feel pain more acutely than others, suggesting that brain hypersensitivity plays a key role in the disease. Swiss researchers say findings from their new study support the use of antidepressants that target the brain's pain sensitivity center in the treatment of the disorder.
The study, conducted at Geneva University Hospital, compared pain sensitivity among fibromyalgia patients and healthy "control" patients. Patients with fibromyalgia were found to be far less tolerant of different pain stimuli, including heat, cold, and electrical stimulation.
Lead researcher Jules Desmeules, MD, says the findings could lead to better ways to diagnose and treat fibromyalgia.
"This study supports prior evidence of central sensitization in these patients," Desmeules tells WebMD. "It further contributes to the understanding of this sensitization by showing that alterations of the pain system exist outside of the (areas associated with fibromyalgia pain), which suggests that the whole central nervous system is involved."
It is believed that 3.7 million Americans over the age of 18 have fibromyalgia -- a confusing disease characterized by pervasive pain throughout the body that cannot be traced to a specific physical cause. Women are far more likely to be diagnosed with the condition than men. In addition to chronic pain, symptoms frequently include chronic fatigue, headaches, sleep disturbances, and depression.
Several earlier studies confirmed an increased sensitivity to touch and temperature among patients with fibromyalgia, suggesting altered brain processing of pain stimuli. In this study, published in the May issue of the journal Arthritis and Rheumatism, Desmeules and colleagues further examined pain response in people with the disease.
Eighty-five fibromyalgia patients were included in the study, along with 40 people without the disease matched for age and sex. All of the participants were middle-aged, nine out of 10 were women, and the average duration of fibromyalgia among patients was eight years.
Participants were subjected to a battery of sensory tests, including evaluations of sensitivity to heat and cold, mechanical pressure tests, and electrical stimuli. Fibromyalgia patients scored significantly higher in pain sensitivity and lower in pain tolerance than the controls. For example, patients were 66% less tolerant of cold pain than non-patients, and they scored an average of 50% lower in tests of pain reflex (the anguish they felt in response to physical contact.)
"This is another study that suggests the primary problem in people with fibromyalgia is central sensitization," rheumatologist Don Goldenberg, MD, tells WebMD. "But the authors used a novel and very exciting approach, which could definitely simply the diagnosis of this disease."
He says the finding of a potential central nervous system trigger may explain why fibromyalgia patients tend to respond better to antidepressants than to pain relievers such as nonsteroidal anti-inflammatory drugs (NSAIDs). Most antidepressants target the brain's pain centers, while NSAIDs target pain at its source.
Goldenberg says his own studies have shown the tricyclic antidepressant Elavil to work well in fibromyalgia patients, but the drug has a long list of potential side effects. Newer antidepressants in the class known as selective serotonin reuptake inhibitors (SSRIs) have few side effects, and have also been shown to reduce pain associated with fibromyalgia. Prozac, Paxil, and Zoloft are three widely prescribed SSRIs.
"If any pharmacologic intervention is useful in fibromyalgia patients, it has been antidepressants," says Goldenberg, who directs the Arthritis-Fibromyalgia Center at Newton-Wellesley Hospital in Newton, Mass.