| One-Minute Clinician

Small Fiber Neuropathies

We don’t have very precise tools to evaluate the way the nervous system functions. We have electrophysiological studies like EMG and nerve conduction velocity assessments, but they’re often negative in people who have widespread or other localized pain complaints, and people have been told that that means that there’s nothing wrong with them. But what’s been underappreciated is that an EMG or nerve conduction velocity test only measures the largest nerve fibers and not the small fibers. Small fibers, meaning weakly or unmyelinated nerve fibers, are the ones that control pain or transmit pain information. The large nerve fibers don’t.  So for years, we’ve been addressing painful disorders with a tool that doesn’t measure the nerve fiber types that are involved in pain processing.

It’s been demonstrated in a wide variety of chronic painful conditions, that the major pathological state is the reduction of nerve fiber density in the skin of individuals who have chronic widespread complaints. We’ve learned that this occurs in individuals who have a wide variety of painful neuropathies such as pain associated with chemotherapy-induced neuropathy, for example. This is exciting because a more refined diagnosis is a step to providing better treatment. The most common known cause of small fiber neuropathy is glucose intolerance, but also included in that spectrum is metabolic syndrome and other conditions. So if we can identify a separate medical process in someone earlier, undiagnosed metabolic syndrome and treat them appropriately, perhaps that will help. More importantly, we’re starting to realize that certain advance therapies--IV gamma globulin, IViG, for example can be helpful in different types of small fiber neuropathy conditions. That is an avenue of treatment to arrest the process that is just being explored. There are only a handful of small studies, but this is an opportunity we haven’t had in years to help people.

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