Small Fiber Functionality in Patients with Diabetic Neuropathic Pain

Area of Science:

• Neurology
• Diabetology
• Pain Management

Background:

• Diabetic neuropathic pain is frequently linked to small fiber neuropathy.
• Assessing small fiber functionality in diabetic patients presents a clinical challenge.

Purpose of the Study:

• To evaluate small fiber functionality in patients with diabetes using a practical method.
• To introduce Laser Speckle Contrast Analysis (LASCA) as a tool for assessing axon-reflex flare responses.

Main Methods:

• Included patients with impaired glucose tolerance (IGT), diabetic neuropathic pain (DNP), type II diabetes without pain, and healthy controls.
• Induced axon-reflex flare responses with capsaicin and histamine, measuring flare characteristics via LASCA.
• Assessed pain/itch responses and verified structural small fiber properties using skin biopsies.

Main Results:

• Patients with DNP exhibited higher pain scores and HbA1c levels.
• Distal intraepidermal nerve fiber densities (IENFDs) were reduced for PGP9.5 and increased for TRPV1 in DNP patients, consistent with length-dependent neuropathy.
• LASCA data indicated small fiber hypo-functionality in IGT and DNP patients, correlating with disease severity.

Conclusions:

• A practical, objective method using axon-flare responses and LASCA for small fiber functionality assessment is presented.
• This method requires no special expertise and can be performed quickly (within 5 minutes).
• LASCA shows potential for early diagnosis of small fiber hypo-functionality in IGT and DNP.