Classification by Symptoms May Aid Treatment of Patients With Fibromyalgia
An analysis of outcome data indicates that patients with fibromyalgia may be classified into one of four symptom domains, each distinguished by greater presence or severity of specific symptoms. The study results suggest an advance toward individualized patient therapy.
“Fibromyalgia is ineffectively treated, and heterogeneity is part of the problem,” said Ann Vincent, MD, a researcher with the Mayo Fibromyalgia Clinic in Rochester, Minnesota. “When a patient comes into the clinic, there is no standardized way to classify the heterogeneity in a way to understand their most bothersome symptom. Different physicians have their own ad hoc methods and choices of medications,” added Dr. Vincent. “What if we could have a better way to assess patients by classifying the illness from their perspective, in terms of their most bothersome symptoms?”
Study investigators used core symptom domains recommended by the fibromyalgia working group of the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) initiative to identify subgroups of patients with similar syndromes. “We were looking to cluster participants according to their response to a comprehensive symptom questionnaire package to identify groups of individuals who reported similar symptom profiles,” said Dr. Vincent.
A total of 581 females with a mean age of 55.1, each with a diagnosis of fibromyalgia, were included for analysis. The patients completed the following outcome measures recommended by OMERACT: the Brief Pain Inventory, 30-item Profile of Mood States, Medical Outcomes Sleep Scale, Multidimensional Fatigue Inventory, Multiple Ability Self-Report Questionnaire, Fibromyalgia Impact Questionnaire-Revised, and Medical Outcomes Short Form-36.
The study investigators used a statistical technique that groups or clusters similar observations or values to identify subgroups of patients. They found four clusters distinguished by differences in symptomatology and pain severity.
Patients in Cluster 1 had the lowest average levels of all symptoms, and patients in Cluster 4 had the highest levels. The researchers found differences between the clusters that reflected moderate symptom levels: Clusters 2 and 3. Patients in Cluster 2 had less depression, anxiety, and dyscognition, also known as the “fibro fog,” but had more pain, stiffness, dysfunction, sleep disturbances, and fatigue than the patients in Cluster 3.
If a patient’s scores place her in Cluster 1, a clinician might consider initial management with nonpharmacologic treatments, such as cognitive behavioral therapy, exercise, physical therapy, and education for self-management of symptoms, with the option of adding pharmacologic therapies if initial treatment response fails, said Dr. Vincent. Patients in Cluster 4 might be preferentially triaged to intensive pain rehabilitation, given that regular outpatient treatment is frequently ineffective in this patient population, she added. “Obviously, this needs to be studied, and this is our next step,” Dr. Vincent concluded.
Conditioned Pain Modulation May Correlate With Decreased Activity in the Spinal Cord
Conditioned pain modulation (CPM), a measure of the brain’s ability to regulate pain, decreases activity in the human spinal cord, according to researchers. The decreased activity is visible through functional MRI (fMRI).
“This study confirmed our hypothesis that CPM results in significant reductions in spinal dorsal horn activity in humans,” said Ian Mackey, student research assistant at Stanford University in Palo Alto, California.
Recent research has focused on the brain’s ability to regulate the pain experience, which is reduced in patients with chronic pain. The CPM effect is the reduced pain rating of a test stimulus, also described as “pain inhibiting pain.”
Low CPM efficiency has been associated with the development of various pain syndromes, including irritable bowel syndrome, temporomandibular disorders, fibromyalgia, and tension type headache. Some reports have linked low CPM efficiency with neuropathic pain.
Working with the hypothesis that CPM would reduce fMRI activity in the human spinal dorsal horn, the investigators used a standard CPM task in which the test stimulus of heat pain was applied to the left forearm twice, once with and once without the CPM component (ie, a foot immersed in a bath of water at 12 °C). The investigators collected two separate fMRI scans.
The researchers found significant activity within the ipsilateral dorsal horn; fMRI activity was significantly less during the test stimulus plus CPM, compared with the test stimulus alone. Furthermore, changes in spinal cord activity correlated with the changes in perceived pain reduction resulting from CPM.
Subjecting healthy participants to fMRI scans during noxious stimuli has enabled researchers to create high-resolution, neuronal activation maps of the human cervical spinal cord. “We hope these findings will serve as a platform for investigation of abnormal spinal pain inhibitory systems in human chronic pain conditions and will help with targeting effective therapies for chronic pain,” said Mr. Mackey.