What is the difference between large fiber polyneuropathy, mononeuropathy, and small fiber polyneuropathy?

From the Guidelines

The main difference between large fiber neuropathy, mononeuropathy, and small fiber polyneuropathy lies in the types of nerves affected and the pattern of involvement, with large fiber neuropathy affecting myelinated A-alpha and A-beta nerve fibers, mononeuropathy involving damage to a single peripheral nerve, and small fiber polyneuropathy affecting unmyelinated C-fibers and thinly myelinated A-delta fibers, as noted in the most recent guidelines 1.

Key Differences

• Large fiber neuropathy affects the myelinated A-alpha and A-beta nerve fibers responsible for vibration sense, proprioception, and motor function, typically causing symptoms like numbness, tingling, weakness, and loss of balance.
• Mononeuropathy involves damage to a single peripheral nerve, resulting in symptoms confined to that nerve's distribution area, such as carpal tunnel syndrome affecting the median nerve.
• Small fiber polyneuropathy affects the unmyelinated C-fibers and thinly myelinated A-delta fibers that transmit pain and temperature sensations, causing burning pain, abnormal temperature sensations, and autonomic dysfunction like sweating abnormalities.

Diagnostic Approaches

• Large fiber neuropathy is often detectable on nerve conduction studies.
• Mononeuropathy shows abnormalities in a single nerve distribution.
• Small fiber neuropathy requires specialized tests like skin biopsy for small nerve fiber density or quantitative sensory testing since routine nerve conduction studies are often normal, as highlighted in recent research 1.

Clinical Implications

• Early recognition and appropriate management of neuropathy in people with diabetes is crucial, as emphasized in the latest standards of care 1.
• Glycemic control can effectively prevent diabetic peripheral neuropathy and cardiac autonomic neuropathy in type 1 diabetes and may modestly slow their progression in type 2 diabetes, but it does not reverse neuronal loss, as noted in previous studies 1.

From the Research

Differences between Large Fiber, Mono, Neuropathy, or Small Fiber Polyneuropathy

• Large fiber neuropathy affects the larger nerve fibers, which are responsible for motor function, vibration, and proprioathy [(2,3)].
• Mono neuropathy refers to the damage or dysfunction of a single peripheral nerve 4.
• Neuropathy is a general term for nerve damage, which can affect any type of nerve fiber [(5,6)].
• Small fiber polyneuropathy, also known as small fiber neuropathy (SFN), affects the small nerve fibers, including A-delta and C fibers, which are responsible for pain, temperature, and autonomic function [(2,3,4,5,6)].

Characteristics of Small Fiber Neuropathy

• SFN is characterized by symptoms such as neuropathic pain, sensory disturbances, and autonomic dysfunction [(2,3,4,6)].
• The diagnosis of SFN is often challenging and requires a combination of clinical evaluation, laboratory tests, and skin biopsy [(2,3,4,5,6)].
• SFN can be caused by various factors, including metabolic diseases, immune-mediated disorders, genetic abnormalities, and vitamin deficiencies [(2,3,4,5,6)].

Diagnostic Criteria for Small Fiber Neuropathy

• The diagnosis of SFN is based on a combination of clinical features, such as pain, sensory disturbances, and autonomic dysfunction, and abnormal diagnostic tests, including skin biopsy and quantitative sensory testing [(2,3,4,5,6)].
• The diagnostic criteria for SFN include reduced intraepidermal nerve fiber density on skin biopsy and abnormal quantitative sensory testing results [(3,5,6)].