Clinical neurophysiology and imaging of nerve injuries: preoperative diagnostic work-up and postoperative monitoring

Peripheral nerve injuries are a heterogeneous group of lesions that may occurs secondary tovarious causes. Several different classifications have been used to describe the pathophysiologicalmechanisms leading to the clinical deficit, from simple and reversible compression‑induceddemyelination, to complete transection of nerve axons. Neurophysiological data localize, quantify,and qualify (demyelination vs. axonal loss) the clinical and subclinical deficits. High‑resolutionultrasound can demonstrate the morphological extent of nerve damage, fascicular echotexture(epineurium vs. perineurium, focal alteration of the cross‑section of the nerve, any neuromas, etc.),and the surrounding tissues. High field magnetic resonance imaging provides high contrastneurography by fat suppression sequences and shows structural connectivity through the useof diffusion‑weighted sequences. The aim of this review is to provide clinical guidelines for thediagnosis of nerve injuries, and the rationale for instrumental evaluation in the preoperative andpostoperative periods. While history and clinical approach guide neurophysiological examination,nerve conduction and electromyography studies provide functional information on conductionslowing and denervation to assist in monitoring the onset of re‑innervation. High‑resolution nerveimaging complements neurophysiological data and allows direct visualization of the nerve injurywhile providing insight into its cause and facilitating surgical treatment planning. Indications andlimits of each instrumental examination are discussed.