Fibromyalgia is a common chronic pain condition that affects millions of individuals worldwide. Those with fibromyalgia often experience widespread pain throughout their body, along with other symptoms like fatigue and cognitive difficulties. This often leads to questions about whether the nerve-like sensations associated with fibromyalgia indicate a connection to conditions involving nerve damage, such as neuropathy. Exploring this relationship is important for understanding the distinct characteristics of each condition and how they might overlap.
Understanding Fibromyalgia
Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, often described as a constant, dull ache. This pain typically occurs on both sides of the body, above and below the waist, and has been present for at least three months. Beyond pain, individuals with fibromyalgia commonly experience significant fatigue, unrefreshing sleep, and cognitive issues often called “fibro fog,” including problems with memory and concentration.
Fibromyalgia is a disorder of pain processing. The brain and spinal cord amplify pain signals, leading to increased sensitivity to both painful and non-painful stimuli. Changes in brain chemistry and pain message processing contribute to this heightened sensitivity.
Understanding Neuropathy
Neuropathy refers to damage or dysfunction of peripheral nerves, those outside the brain and spinal cord. These nerves transmit signals between the brain, spinal cord, and body. When damaged, peripheral nerves can cause symptoms including weakness, numbness, tingling, and pain, often in the hands and feet. Sensations can be described as burning, shooting, or prickling.
Neuropathy can stem from various causes, such as diabetes, injuries, infections, autoimmune diseases, or certain medications. While symptoms vary depending on affected nerves, neuropathy is characterized by actual nerve fiber damage. This distinguishes it from conditions involving pain processing without direct nerve damage.
Investigating the Connection
Fibromyalgia does not directly cause damage to large nerve fibers typically affected in conditions like diabetic neuropathy. However, a direct link between fibromyalgia and nerve damage, particularly small nerve fibers, has been a significant research area. The neuropathic-like pain in fibromyalgia often prompts this inquiry, even when conventional nerve tests show no large fiber damage.
Research indicates a notable association between fibromyalgia symptoms and Small Fiber Neuropathy (SFN), which involves damage to small nerve fibers in the skin responsible for sensations like pain and temperature. Symptoms of SFN can closely resemble those of fibromyalgia, including burning pain, tingling, numbness, and heightened sensitivity to touch (allodynia).
Studies show a subset of individuals with fibromyalgia also have objective evidence of SFN. Skin biopsies, which assess intraepidermal nerve fiber density, reveal reduced nerve fiber density in some fibromyalgia patients, supporting this connection. While not all fibromyalgia patients show signs of SFN, research suggests 40% to 50% may have objective evidence of small fiber damage.
Individuals can also experience both fibromyalgia and another form of neuropathy, such as diabetic neuropathy, as distinct but co-occurring conditions. The complex interplay between central pain processing and peripheral nerve changes means that in some patients, shared underlying mechanisms, such as immune system dysfunction or inflammation, might contribute to both conditions.
Identifying Distinctive Features
Medical professionals differentiate fibromyalgia and neuropathy through a comprehensive evaluation including medical history, physical examination, and specific diagnostic tests. Fibromyalgia is diagnosed based on widespread pain, fatigue, and cognitive issues, without objective markers of nerve damage in standard tests. Neuropathy, conversely, often presents with objective signs of nerve damage.
To diagnose neuropathy, common tests include Nerve Conduction Studies (NCS) and Electromyography (EMG). These tests assess larger nerve fiber and muscle function, helping identify damage. However, NCS and EMG typically appear normal in pure SFN cases, as they do not evaluate small nerve fibers.
For SFN, specialized tests like skin biopsies are used. A skin biopsy involves taking a tissue sample to measure intraepidermal nerve fiber density, providing direct evidence of small nerve fiber damage. These tests help confirm or rule out nerve damage, guiding treatment. Pain patterns also offer clues: fibromyalgia typically presents as generalized, diffuse pain, while neuropathy often has more localized pain or follows specific nerve distributions, especially in the hands and feet.