Neuropathy: Maybe it's all connected...
Updated: May 26, 2019
Do you have any of these?
1. Relentless, profound physical fatigue
2. Brain fog: Mental fatigue/cognitive changes
3. Dizziness or lightheadedness with prolonged standing
4. Widespread muscle pain / fibromyalgia
5. GI motility issues: nausea, constipation, diarrhea, bowel cramping, swallowing problems
6. Burning feet (or other parts of the body). Shooting pains, unexplained itching, buzzing, cold, numbness or tingling sensations.
7. Burning pain in the eyes or mouth.
Each of these symptoms may be caused, at least in part, by a common neurologic problem seen in Sjogren’s: Small fiber neuropathy (SFN). Small fibers are the unmyelinated nerves outside the brain and spinal cord that detect sensations and control autonomic functions such as heart rate, blood pressure, bowel motility, sweating, etc. Neuropathy means that these nerves are not working correctly. In SFN, the number of nerve fibers is often reduced on skin biopsy. Sensory neuropathy and autonomic neuropathies frequently occur together. (33) Neuropathies of myelinated nerves (medium to large fibers) also occur in Sjogren’s, but are not discussed in this blog post.
Researchers are just beginning to highlight the role of SFN in Sjogren’s. SFN is sometimes called SFPN (small fiber polyneuropathy) because it usually impacts a widespread area and a large number of nerves. For simplicity, I use the term SFN. While most clinicians are familiar with sensory neuropathies, there is little awareness that SFN causes autonomic dysfunction and/or pain in a large subset, probably a majority, of Sjogren’s patients. Cardiovascular dysautonomias have been shown to cause or contribute to fatigue, lightheadedness and brain fog in Sjogren’s and other conditions. (49, 50, 55)
Routine neurologic exam often does not detect SFN. EMGs do not measure abnormalities in these small unmyelinated nerve fibers. Autonomic testing (tilt table, sweat testing etc.) and skin biopsy are usually needed to confirm typical SFNs. These tests require special training and equipment. Right now, this usually requires travel to a research center. Even then, the testing is not perfect. Patients occasionally require repeat evaluation to have the diagnosis of sensory neuropathy or dysautonomia confirmed. Sometimes treatment is based on clinical history.
If you think you might have dysautonomia(s) or sensory neuropathy, try to find a neurologist familiar with these features and Sjogren’s. Otherwise, you may end up with a psychology/ psychiatry referral, and no real evaluation. Likewise, if you plan to see a gastroenterologist or cardiologist for what could be dysautonomia, make sure that they are interested in and knowledgeable about the neuropathic causes of these conditions.
In my blog post on 4-11-19, I discussed the leading edge research by Dr. Brent Goodman on Sjogren’s and the autonomic nervous system. (33) In addition to Dr. Goodman’s lecture, I highly recommend the video lectures by the Harvard neurologist, Dr. Anne Louise Oaklander (SFPN) and her colleague, Dr. Khosro Farhad. Dr. Farhad demonstrates that SFPN is the underlying cause of about half of fibromyalgia cases.
Because SFN is so common in Sjogren’s, it is likely that the “fibromyalgia” label is simply picking up on a direct Sjogren’s manifestation. There are many stories of Sjogren’s patients who were initially diagnosed with fibromyalgia. Their Sjogren’s symptoms may have been incomplete early on, or more likely, their clinicians were unfamiliar with Sjogren’s. I am not alone in the opinion that every patient labeled with fibromyalgia should be evaluated for possible Sjogren’s. Likewise, Dr. Goodman and Dr. Oaklander promote Sjogren’s screening in dysautonomia and sensory neuropathy patients who do not have another obvious cause for SFN. Many Sjogren’s patients have unrecognized SFNs.
What can be done if you have SFN? Doctors Goodman, Oaklander and Farhad discuss testing and treatment in their videos. Some conditions have symptomatic treatments and lifestyle interventions that can greatly improve comfort and function. Treating the underlying immune system problem is often helpful, but remains challenging due to medication side effects, expense, and inadequate research data.
Sjogren’s experts have called general systemic features such as fatigue, pain and brain fog “the great unmet need.” Many patients state that finding treatments for these life-altering manifestations is their highest priority. While fatigue and pain are complex clinical issues, the recent understanding of the role of SFN/dysautonomia should make these topics a high priority for research.