Small Fibre Neuropathy

One of the most confusing aspects of neuropathy for the patient, is the number of names and titles which are given to its different forms. If you're researching information, you will often come across the term, 'small fibre neuropathy' or 'small fibre sensory neuropathy'. If you are diagnosed with SFN you may also hear the description 'Idiopathic neuropathy' which basically means, they can't find the physical evidence they need to back up your symptoms but idiopathic neuropathy is generally, essentially, also small fibre neuropathy and to make the waters even more muddy, you may also and in the same breath, be told you have symptoms of autonomic neuropathy (there are posts about autonomic neuropathy elsewhere in the blog - see list to the right).

The important thing is not to panic - each one of these titles may describe the same thing and apply to your form of neuropathy but the doctor may not have the time to explain the subtle differences in the course of a consultation. Time to do your own research then and therefore today's post tackles Small Fibre Neuropathy and comes from the always reliable Johns Hopkins Medicine site (see link below). Just to be clear, the letters SSFN they use, refer to the title, Small Fibre Sensory Neuropathy.

Small Fiber Sensory Neuropathy

Small fiber sensory neuropathy (SFSN) is a disorder in which only the small sensory cutaneous nerves are affected. The majority of patients experience sensory disturbances that start in the feet and progress upwards. These patients have what is called a length-dependent SFSN. This type of SFSN is often due to diabetes or impaired glucose metabolism (i.e. early or pre-diabetic state) and may progress to typical diabetic polyneuropathy. However, in a significant percentage of patients, no underlying etiology is found and the patients have idiopathic SFSN. A small percentage of patients with SFSN experience sub-acute onset sensory disturbances diffusely over the whole body, including the trunk and sometimes even the face. These patients have non-length-dependent SFSN and almost all cases are idiopathic.

Symptoms

The symptoms of small fiber sensory neuropathy are primarily sensory in nature and include unusual sensations such as pins-and-needles, pricks, tingling and numbness. Some patients may experience burning pain or coldness and electric shock-like brief painful sensations. Since SFSN usually does not involve large sensory fibers that convey balance information to the brain or the motor nerve fibers that control muscles, these patients do not have balance problems or muscle weakness. In most patients, these symptoms start in the feet and progress upwards. In advanced cases, it may involve the hands.

Diagnosis

Diagnosis of SFSN is based on history, clinical examination and supporting laboratory investigations. Electromyography and nerve conduction studies are done to eliminate involvement of motor and large sensory nerve fibers. Skin biopsies are used to confirm loss of cutaneous nerve innervation. Nerve and muscle biopsies are rarely needed.

Treatment

Treatment of SFSN depends on the underlying etiology. If it is due to diabetes or pre-diabetic state, then optimum diabetic control and exercise and weight loss to reduce insulin resistance are needed. Painful sensory paresthesias can be treated with anti-seizure medications such as gabapentin (Neurontin), pregabalin (Lyrica) and topiramate (Topamax), antidepressants such as amitriptyline (Elavil) and duloxetine (Cymbalta), or analgesics including opiate drugs. In severe painful conditions patients may be referred to the Blaustein Chronic Pain Clinic for a multidisciplinary approach to pain management.

http://www.hopkinsmedicine.org/neurology_neurosurgery/specialty_areas/peripheral_nerve/conditions/small_fiber_sensory_neuropathy.html