Neuropathy Commons

Translating today's discoveries into tomorrow's cures

User Top Menu

Diagnosing Small Fiber Polyneuropathy

by Dr. Onyema Nnanna

Diagnosis of medical illness often starts with a through history then a physical examination to suggest possible diagnoses. This is often followed by testing to help sort through the possibilities. No test is 100% accurate, but test results can provide independent objective evidence about whether a particular diagnosis is or is not true.

Three tests are recommended by the American Academy of Neurology or the European Academy of Neurology: skin biopsy, autonomic function testing, and nerve biopsy.

Skin biopsy: A tiny skin core is removed from a specific spot on the lower leg using local anesthesia. This is quite safe and does not require stitches. A biopsy can be removed in a doctor’s office anywhere and mailed to one of the special pathology laboratories that can process and examine it. For listings of doctors who perform skin biopsies for diagnosing peripheral neuropathy around the world click here. Alternatively, most hospitals that analyze these biopsies also have someone who performs them. To arrange to have a skin biopsy performed at Massachusetts General Hospital, click here. Once a biopsy arrives at the laboratory, tiny sections of it are exposed to chemicals that make the nerve fibers within them visible (immunohistochemistry), and the number of nerve fibers in the surface layer (epidermis) is counted and compared to expected normal values. If the number of nerve fibers is very reduced from normal, this is accepted evidence that the patient has SFPN.

Autonomic Function Testing (AFT): This is a group of tests performed at the same time to measure a person’s blood pressure and heart rate in response to various circumstances such as being tilted upright on a table. Ability to sweat is also measured. These are considered autonomic functions.

Nerve Biopsy: This is an older technique performed only at special centers including Massachusetts General Hospital. A surgeon remove a small piece of a sensory nerve under anesthesia, usually from the lower leg, and send it for pathological study. For many but not all patients, skin biopsy can replace nerve biopsy. Nerve biopsies remain useful for detecting inflammatory causes of neuropathies such vasculitis and sarcoidosis, and for diagnosing nerve tumors or infections such as leprosy.

If you have been diagnosed with polyneuropathy, your clinician may order tests to identify its underlying medical cause. Many such causes can be treated, offering the possibility for improvement of the neuropathy and its symptoms.

References:

  1. England, JD, Gronseth, GS, Franklin, G, et al. Practice Parameter: Evaluation of distal symmetric polyneuropathy: role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review). Report of the American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and American Academy of Physical Medicine and Rehabilitation. Neurology. 2009;72:177-184.
  2. Lauria, G, Cornblath, DR, Johansson, O, et al. EFNS guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy. Eur J Neurol. 2005;12:747-758. Assessment: Clinical autonomic testing report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 1996;46:873-880.