Measurement of median nerve blood flow during carpal tunnel release with laser Doppler flowmetry

Eight consecutive median nerves in eight patients with clinical carpal tunnel syndrome were prospectively examined by non-contact laser Doppler flowmetry before and after undergoing carpal tunnel release. Before performing carpal tunnel release, the difference in the median nerve blood flow between the values at the distal and proximal portions to the transverse carpal ligament was statistically significant (p=0.021). After carpal tunnel release, the median nerve blood flow both distal and proximal to the transverse carpal ligament increased by 1.5 and 1.3 times, respectively, compared to the flow prior to carpal tunnel release, however, only the difference at the distal portion to the transverse carpal ligament was statistically significant (p=0.015). In this study, we directly measured the median nerve blood flow using non-contact laser Doppler flowmetry and thus demonstrated a significant difference in the median nerve blood flow between the values at the distal and proximal portions to the transverse carpal ligament before carpal tunnel release and a significant increase in the nerve blood flow only at the distal portion to the transverse carpal ligament after surgery. This technique is thus considered to be an easy and reproducible way to intraoperatively evaluate the nerve blood flow in real time during the release of entrapment neuropathies.