BY PATRICIA INACIO, PHD
Dysfunction in spinal cord processing may be responsible for pain in fibromyalgia (FM) patients, according to a study titled “Lengthened Cutaneous Silent Period in Fibromyalgia Suggesting Central Sensitization as a Pathogenesis” and published in the journal PLOS One.
Fibromyalgia is characterized by chronic widespread pain, among other symptoms, but the underlying cause responsible for chronic pain in FM remains unclear. Recent and accumulating evidence suggests that central pain amplification is key for fibromyalgia pathogenesis: a process characterized by augmented pain and sensory processing in the spinal cord and brain, also known as “central sensitization.”
Researchers compared the cutaneous silent period (CSP), a spinal reflex mediated by A-delta cutaneous afferents used to assess pain processing in both the central and peripheral nervous systems, between fibromyalgia patients and normal healthy controls. A total of 24 fibromyalgia patients (diagnosed according the 1990 American College of Rheumatology classification system) and 24 age- and sex-matched healthy controls were analyzed. Researchers measured CSP from the abductor pollicis brevis muscle (located in the hand between the wrist and the base of the thumb) using standard electrodiagnostic equipment, along with patients’ parameters including demographic data, number of tender points, visual analog scale and fibromyalgia impact questionnaire scores.
Mean CSP duration was significantly longer in fibromyalgia patients when compared to healthy controls. Previous studies investigating CSP in patients with central nervous disorders had found that CSP duration was prolonged in brachial dystonia, Parkinson’s disease, and multiple system atrophy. These findings suggest that CSP duration may reflect dysfunction of supraspinal control, which will cause an impact on spinal excitability.
These findings suggest fibromyalgia is associated with dysfunction of pain modulation mechanisms in the central nervous system. Notably, researchers found no correlation between CSP and clinical parameters such as VAS score, K-FIQ score, age, and height, which poses doubts as to whether to use CSP to assess disease severity. Accordingly, researchers emphasize that additional studies are required to further evaluate the relationship between CSP parameters and clinical data.
“In conclusion, dysfunction of supraspinal control may be responsible for pain in FM, providing further evidence that central sensitization underlies the pathogenesis of the disease,” the authors write in their report.