Electroneurography during facial nerve expansion

With the use of tissue-expansion techniques, it is possible to elongate the facial nerve without impairing its function. The rate of expansion is limi ted by ischemic events imposed by stretching of the nerve and by anatomic c haracteristics of the nerve segment. In this study, we used various electro neurography techniques to determine the first sign of facial dysfunction du ring expansion. The main objective of the study was to ascertain test-retes t variability of electroneurography techniques. Facial nerves were expanded in 16 cats with the use of a tissue expander secured more deeply to the ma in trunk. We conducted electroneurography measurements with the use of surf ace electrodes, temporary needle electrodes, and permanently implanted elec trodes. Technique-dependent variations encountered with the surface electro des made this method unreliable. Using implanted electrodes, we noted gradu al worsening of the compound-action potential amplitude with increasing exp ansion. During acute expansion, reduction in compound-action potential ampl itude was correlated with clinically observed deterioration of facial-nerve function. In this study, electroneurography with implanted electrodes was found to be the most reliable predictor of the rare of successful facial ne rve expansion.