[3] In some instances, the small fibers of the autonomic nervous system can be affected, leading to urinary or bowel problems, episodes of rapid heartbeat (palpitations), dry eyes or mouth, or abnormal sweating.
They can also experience a sharp drop in blood pressure upon standing (orthostatic hypotension), which can cause dizziness, blurred vision, or fainting.
The NaV1.7 and NaV1.8 sodium channels are found in nerve cells called nociceptors, that transmit pain signals to the spinal cord and brain.
The cause of this degeneration is unknown, but likely accounts for some of the signs and symptoms of the disorder, such as the loss of temperature differentiation and pin-prick sensation.
The combination of increased pain signaling, and degeneration of pain-transmitting fibers, leads to a variable condition with signs and symptoms that can both vary and change over time.
[4] In diabetics who rapidly reduce their HbA1c value by over 3 percentage points within a short time frame (3-6 months), a temporary form of SFN often results.
[14] Quantitative sensory testing (QST) assesses small fiber function by measuring temperature and vibratory sensation.
[13] Electrochemical skin conductance has been evaluated for both early diagnosis of small fiber neuropathy and follow-up of treatment efficacy.
[13] Physicians can biopsy the skin with a 3-mm circular punch tool and immediately fix the specimen in 2% paraformaldehyde lysine-periodate or Zamboni's fixative.
[20] Specimens are sent to a specialized laboratory for processing and analysis where the small nerve fibers are quantified by a neuropathologist to obtain a diagnostic result.
[21] The following table describes the IENFD values in males and females of a 3 mm biopsy 10 cm above the lateral malleolus (above ankle outer side of leg).
In the remaining patients conditions more prevalent than reported literature findings were autoimmune diseases, sodium channel gene mutations, diabetes mellitus including glucose intolerance, and vitamin B12 deficiencies.