# Fluorescein Angiography for Monitoring Neural Blood Flow in Chronic Nerve Compression Neuropathy: Experimental Animal Models and Preliminary Clinical Observations

## TL;DR

This study explores the use of fluorescein angiography to monitor blood flow in nerves affected by chronic compression, showing promising results in both animal models and clinical cases.

## Contribution

The study introduces fluorescein angiography as a novel and reliable method for assessing neural blood flow in severe nerve compression neuropathy.

## Key findings

- Fluorescein angiography effectively monitored reduced neural blood flow in CNC rat and rabbit models.
- Fluorescein angiography correlated strongly with compound muscle action potential amplitude, unlike laser Doppler flowmetry.
- Fluorescein angiography showed significant correlation with preoperative electrodiagnostic findings in clinical CTS cases.

## Abstract

Pathologies associated with neural blood disturbance have been reported in patients with chronic nerve compression (CNC) neuropathy. Fluorescein angiography (FAG) and laser Doppler flowmetry (LDF) are effective for real-time peripheral nerve blood flow assessment. However, their reliability in severe neuropathy models in large animals or clinical conditions remains unclear. Initially, we aim to apply FAG to two different CNC animal models and evaluate their characteristics in comparison with those of LDF. In FAG, we quantified the peak luminance at the compression site following fluorescein injection. Then, we positioned the LDF probe at the center of the compression site and recorded the blood flow. Subsequently, we analyzed whether the FAG characteristics obtained in this animal experiment were consistent with those of clinical studies in patients with severe carpal tunnel syndrome (CTS). In the CNC rat model, FAG and LDF effectively monitored reduced neural blood flow over time. We observed significant blood flow reduction using both techniques in a newly developed severe CNC rabbit model. Notably, FAG correlated strongly with the compound muscle action potential (CMAP) amplitude in electrodiagnostic findings, unlike LDF. As a next step, we performed FAG after open carpal tunnel release in clinical cases of CTS. FAG correlated significantly with preoperative CMAP amplitude. This indicates FAG’s importance for assessing nerve blood flow during surgery, potentially improving diagnostic accuracy and surgical outcomes.