This pilot study aims to investigate the effects of nerve blocks in patients with diabetic peripheral neuropathy through a double-blinded, randomized trial involving 4 patients. Each participant will receive bilateral peripheral nerve blocks using either lidocaine or papaverine. Following randomization, each patient will receive one medication in one leg and the alternate medication in the contralateral leg. Researchers will measure parameters including motor strength, sensory function (two-point discrimination), arterial blood flow via Doppler ultrasound, and microvascular perfusion using near-infrared spectroscopy both prior to and following nerve block administration. This research seeks to explore potential diagnostic and therapeutic applications for peripheral nerve entrapment, a common yet challenging clinical condition.

Detailed Analysis of the Phoenix Sign and Vascular Changes Following Nerve Blocks in Diabetic Neuropathy

Study Background and Purpose

This study investigates the vascular and neurological phenomena associated with peripheral nerve blocks in patients with diabetic neuropathy. The primary aim is to assess whether observed changes following nerve block administration can be attributed to vasodilatory effects of lidocaine or neurological mechanisms.

Common peroneal nerve (CPN) entrapment is the third most common nerve entrapment pathology in humans and frequently results in foot drop, characterized by difficulty lifting the front part of the foot.

Study Design and Methodology

This pilot study is a double-blinded, randomized trial involving 4 diabetic patients presenting bilateral anterior compartment weakness affecting dorsiflexion. All participants will have confirmed diabetic neuropathy with severe sensory impairment.

Key methodological elements:

Randomized administration of 0.5 cc of papaverine HCL (30 mg/ml) or 0.5 cc of 1% lidocaine without epinephrine.

Initial randomization of the first leg via coin toss, with the contralateral leg receiving the alternate medication.

Double-blinded design, ensuring neither patients nor evaluating physicians are aware of medication allocation for each leg.

Ultrasound-guided perineural injection at the fibular neck level.

Comprehensive pre- and post-injection assessments.

Study assessments include:

Macrovascular assessment:

Ultrasound Doppler waveform analysis.

Measurement of blood flow velocity in dorsalis pedis and posterior tibial arteries.

Microvascular assessment:

Kent Snapshot Near-Infrared (NIR) imaging of dorsal and plantar foot surfaces.

Measurement of hemoglobin, deoxyhemoglobin, oxygen saturation (SpO2), and total hemoglobin.

Imaging scheduled pre-injection, at 4 minutes post-injection, and at 10 minutes post-injection.

Motor function assessment:

Movement Against Manual Resistance (MAMR) scored from 1-5 (normalized to 0.2-1.0).

Evaluation of three muscles: extensor hallucis longus (EHL), tibialis anterior (TA), and extensor digitorum longus (EDL).

Dynamometer measurements of EHL muscle strength (Newtons, N).

Sensory assessment:

Two-point discrimination testing

Inclusion Criteria:

• subjects were included if they were diabetic and neuropathic.

Exclusion Criteria:

• Patients with Trypanophobia