In Vivo Fascicle Bifurcation Imaging of Rat Sciatic Nerve Using Swept-Source Optical Coherence Tomography

The sciatic nerve is the longest and widest single nerve in the human body and is responsible for the signal transduction of the entire hind limb region. Its wide nerve dynamic range and size makes it sensitive to injury. The branching and location of the sciatic nerve are important, and unlike histology, optical coherence tomography (OCT) can provide rapid non-destructive cross-sectional images. The sciatic nerves of ten rats were analyzed using swept-source (SS)-OCT. The sufficient depth penetration of the SS-OCT system allowed clear identification of the internal bifurcation point of the external branching and the internal route for the three terminal nerves in cross-sectional images. Internal bifurcation is observed through interfascicular epineurium resulting from epineurium division. Two bifurcations occur at the bottom of the sciatic nerve. The first and second bifurcations occur approximately 7 and 5 mm, respectively, above the external branching. SS-OCT enabled visualization of surgical needle positioning during direct injections into the sciatic nerve, which is beneficial for drug injection or microelectrode placement for electrical signal processing as a nerve detection guide. Therefore, analysis of the internal structure obtained in real time and needle position information inside the nerve are expected to act as a guide for neurosurgery.