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Small fiber neuropathy: A burning problem

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Treatment of other diseases

It has also been reported that treatment of sarcoidosis, autoimmune diseases, and celiac disease improved the symptoms of small fiber neuropathy resulting from these conditions.8,31 Therefore, it is important to identify the cause and treat it to prevent and slow the progression of small fiber neuropathy, and doing so may improve the disease in some mild cases.

Pain management

Pain management is crucial in the treatment of small fiber neuropathy, as neuropathic pain can be debilitating and can cause depression. Pain management often requires a multidisciplinary team, including a primary care physician, a neurologist, a pain specialist, and a psychiatrist. Medications include antidepressants, anticonvulsants, and topical anesthetics (Table 1) as well as narcotic and non-narcotic analgesics and antiarrhythmics. Nonpharmacologic management includes transcutaneous electrical nerve stimulation (TENS), heat, ice, and massage of painful areas (reviewed by Chen et al32 and Galluzzi33).

First-line choices of pain medications are the anticonvulsants gabapentin (Neurontin) and pregabalin (Lyrica), the tricyclic antidepressants amitriptyline (Elavil) and nortriptyline (Aventyl), a 5% lidocaine patch (Lidoderm), and the semisynthetic opioid analgesic tramadol (Ultram). These can be used alone or in combination.

Gabapentin is relatively well tolerated, but drowsiness can occur, especially with high starting doses. We usually start with 300 mg daily and increase it by 300 mg every week up to 1,200 mg three times a day as tolerated. Most patients need 600 to 900 mg three times a day.

Pregabalin is a newer antiepileptic drug, similar to gabapentin but less sedating. It can be started at 75 mg twice a day and gradually increased to 300 mg twice a day as needed. Weight gain and, rarely, swelling of the lower extremities may limit the use of both of these drugs.

Tricyclic antidepressants, such as amitriptyline, nortriptyline, and desipramine (Norpramin), are proven effective in controlling neuropathic pain, although no response with amitriptyline was seen in patients with painful HIV distal sensory neuropathy.34

Lidocaine patch is preferred if the painful area is small. Patients should be instructed to use the patch to cover the painful area 12 hours on and 12 hours off. If it does not provide relief within 1 week, it should be discontinued.

Tramadol is also helpful in treating neuropathic pain. It can be started at 50 mg two to four times a day as needed.

Nonsteroidal anti-inflammatory drugs and selective serotonin reuptake inhibitors are typically less effective than the other drugs mentioned.

Opioids should be reserved for refractory cases, given the potential for addiction, but they are sometimes necessary in patients with disabling pain that does not respond to other drugs.

TENS may be of benefit. The patient controls a pocket-size device that sends electrical signals to leads placed on affected areas.

Alternative therapies for small fiber neuropathy, such as meditation, yoga, and acupuncture, have yet to be studied.

It is also important to explain to patients that the typical course of small fiber neuropathy is relatively benign, as many patients worry about developing weakness and eventually not being able to walk. These concerns and fears can aggravate pain and depression, which can make treatment difficult.

WHAT IS THE PROGNOSIS OF SMALL FIBER NEUROPATHY?

Most patients with small fiber neuropathy experience a slowly progressive course, with symptoms and signs spreading proximally over time.

In one study, only 13% of 124 patients with small fiber neuropathy showed evidence of large-fiber involvement over a 2-year period. 21 None went on to develop Charcot joints, foot ulcers, weakness, or sensory ataxia, as is often seen in patients with long-standing or severe large fiber neuropathy. Neuropathic pain worsened in 30% and resolved spontaneously in 11%.21

Most patients with small fiber neuropathy require chronic pain management. Again, treatment of the underlying cause is important and can improve the prognosis.

We believe that the overall progression of small fiber neuropathy is slow. A longitudinal study with a follow-up longer than 2 years would be useful to confirm this.

TAKE-HOME POINTS

As the population continues to age and as more patients develop diabetes and the metabolic syndrome, the prevalence of small fiber neuropathy will rise. Patients who present to their primary care physicians with painful, burning feet require a thorough diagnostic evaluation, which may include referral for specialized neurodiagnostic testing. Aggressive cause-specific treatment, lifestyle modification, and pain control are key elements of a team approach to managing small fiber neuropathy.

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