Diabetic Small Fiber Neuropathy: Clinical, Electrophysiological and Neurosonographic Study

The aim of work is to study the clinical, electrodiagnostic and neurosonographic characteristics of diabetic patients with small fiber neuropathy in the Egyptian population, and to evaluate both the diagnostic and the prognostic impact of the studied factors on the neuropathy severity and quality of life.

This case-control observational study is aiming to evaluate patients with diabetic small fiber neuropathy in the Egyptian.

Diabetic small fiber neuropathy was defined as both of the following:

A. Typical clinical symptoms of SFN such as burning or sharp pain in toes and feet, and on clinical examination: loss of small fiber modalities (pinprick and temperature), hyperalgesia, allodynia, and/or autonomic signs.

B. Reduced intraepidermal nerve fiber density (IENFD) in distal leg skin punch biopsy.

The study includes 3 groups:

Group I: Patients with diabetic small fiber neuropathy Group II (Control Group): Patients with diabetic mixed small and large fiber neuropathy Group III (Control Group): Subjects without peripheral neuropathy

Clinical evaluation includes: Neuropathic Pain 4 (DN4) questionnaire, 11-point Numeric Pain Scale (NPS), Utah Early Neuropathy Scale (UENS), Toronto Clinical Neuropathy Scale (TCNS), Composite Autonomic Symptom Score (COMPASS-31), an Arabic version, and several anthropometric measures; including: body weight in kilograms, height in centimeters, waist circumference measured in centimeters at the top of the iliac crest, and systolic "SBP" and diastolic "DBP" blood pressure measurement in mmHg.

Electrodiagnostic evaluation includes: routine nerve conduction study, cutaneous silent period by stimulating left median nerve and right sural nerve and recording from the abductor pollicis brevis and tibialis anterior muscles, respectively, bilateral hand-to hand and foot-to-foot sympathetic skin response, and Ewing battery using R-R interval analysis, in addition to the blood pressure tests.

Neurosonographic evaluation includes: bilateral vagal nerve scan at the mid-neck lateral to the thyroid cartilage, left median and right ulnar nerves scan at the mid-forearm, left tibial nerve at the distal ankle 2 to 4 fingerbreadths proximal to the medial malleolus, and right sural nerve 2 to 4 fingerbreadths proximal to the lateral malleolus. Nerves are evaluated for transverse cross-sectional area (CSA).

Severity and outcome measures are assessed using: NPS, TCNS, COMPASS-31, and the index score of Euro Quality of Life -5 Dimensions -5 Levels (EuroQOL-5D-5L), the Arabic version.

Eligibility Criteria:
Inclusion Criteria:

1. Patients diagnosed with diabetes mellitus or impaired glucose intolerance by laboratory investigations including any of the following: HbA1C, fasting blood sugar and 2-hour post prandial blood sugar, and/or antidiabetic medication.
2. Patients presented with small fiber neuropathy (SFN), including all the following:

   A. Typical clinical symptoms of SFN such as burning or sharp pain in toes and feet, and on clinical examination: loss of small fiber modalities (pinprick and temperature), hyperalgesia, allodynia, and/or autonomic signs.

   B. Reduced intraepidermal nerve fiber density (IENFD) in distal leg skin punch biopsy.
3. Age older than 18 years old

Exclusion Criteria:

1. Mental illness that made interviewing ineffective
2. Physical illness leading to language and/or cognitive barrier
3. Other conditions that could cause neuropathy (e.g., chemotherapy, alcohol intake, established vitamin B12 deficiency, established hereditary neuropathy "or first-degree family members", active malignancy, chronic advanced liver or kidney diseases thought to cause neuropathy and history of bariatric surgery).
4. Atrial Fibrillation