Recent Studies Show Link Between Fibromyalgia and Small-Fiber Polyneuropathy

Fibromyalgia (FM) is a musculoskeletal condition that starts in the brain and causes widespread pain in the joints and muscles, coupled with intense fatigue, sleep problems, and mood and memory issues. More than 12 million people suffer from FM, with most of those affected being women between the ages of 25 and 60. The fatigue FM patients feel often leaves them unable to stand well or even get out of bed. Some of the effects of FM culminate in anxiety, depression, tension headaches, irritable bowel syndrome, and temporomandibular joint dysfunction.

People with FM have an overly sensitive pain response and so react more strongly to pain-inducing stimuli. Because the symptoms FM patients experience are also symptomatic of other diseases and disorders, and because they are not always consistent, it can be difficult to obtain a firm diagnosis, often making the road from symptoms to diagnosis long, painful, and isolating. There is no test for FM, so it is difficult to confirm the disorder. It is not as simple as taking blood or an X-ray to confirm the symptoms. In order for a proper diagnosis to occur, doctors must rely on grouping a patient's symptoms into a profile.

In a recent study done at Massachusetts General, it was found that almost half of FM patients have what is known as small-fiber polyneuropathy (SFPN), prompting physicians to call for testing of this disorder in patients with FM. The demand is owed to SFPN having a set criterion established for diagnosing. It is thought that, if this testing is used, it will make it easier to identify patients with FM.

Pain is amplified in this condition, so even the slightest of pain stimuli can make a person overly sensitive. It is believed that in such people, signals are processed differently by the pain centers of the brain and spinal cord. Usually, the symptoms begin after an infection, a traumatic physical encounter, or during a time of intense psychological stress. In some cases, the symptoms accumulate over time. The symptoms of FM mimic other disorders, making diagnosis difficult. To help in this endeavor, certain guidelines and specific physical tests have been set by the American College of Rheumatology. The baseline indices for testing are persistent, widespread pain that lasts at least three months; the absence of any other disorder or disease that could cause trouble with one’s thinking; and feeling tired after waking up.

In small-fiber polyneuropathy, the small nerves become damaged. These supply tactile sensation to the body, help with breathing, regulate heart rate, help in digestion, and control perspiration. It is believed that an immune response causes this harm. Small-fiber polyneuropathy occurs in the peripheral nervous system. Numbness, tingling in the affected area, and burning are the usual symptoms. However, these may travel in an upward trajectory. Usually, they tend to start in adolescence or into mid-adulthood. The pain is centralized in the whole body initially, then, as the patient ages, it extends into the extremities. A genetic component has been identified in a majority of cases. The usual diagnosis involves taking a family and medical history, and performing lab tests and a physical examination. Electromyography and nerve conduction studies are done to eliminate the involvement of motor and large nerve fibers, and skin biopsies are done to verify loss of cutaneous nerve innervation. Experimental protocols are currently being used by researchers for the treatment of FM along with the normal FDA-approved medicines. This approach has been successful in treating small-fiber polyneuropathy in patients with both disorders.

• Growth hormones: These were shown to improve pain tolerance and reduce fatigue in patients, but many found issue with the unexpected side effects and the high cost.
• Cannabis: In many cases, the active ingredient found in cannabis, synthetic THC, was found to be very beneficial for patients with FM. It helped with sleep issues and also aided pain relief. Some side effects were present, but they were not life-threatening.
• Quenpentadine: Short-term use of this anti-psychotic enhances dopamine and serotonin levels and blocks the sympathetic nervous system responses to the brain. Increased fatigue is a side effect, though, which is already a problem for FM patients. For many, this drug is not an ideal long-term solution.