43. Laser-evoked potentials for the assessment of the sensory auricular branch of the facial nerve

Abstract

The sensory auricular branch of facial nerve is rarely investigated in clinical practice and its neurophysiological assessment is completely lacking. Our aim was to verify the possibility to obtain Laser Evoked Potentials (LEPs) by stimulating the auricular concha. 18 volunteers (13 M, 5 F; 23–57 years) were enrolled. Using a Yap laser (beam diameter 4 mm, duration 3msec, intensity twice the pricking perceptive threshold) we stimulated both ears and recorded the cortical responses over the scalp (Cz–Fz). The Latency of N2 (LN2) and P2 (LP2) peaks and the N2–P2 peak–peak amplitude (AMP) were measured and for each measurement a symmetry index (SI) was calculated (lower/higher value). Results Typical N2-P2 complexes were recorded in 16 out of 18 subjects. For the stimulation of right ears LN2 and LP2 were 147 + 14.6 and 224 + 18.1 msec respectively, and AMP was 56,6 + 38.8 uV. For the stimulation of left ears LN2 and LP2 were 151 + 14 and 231 + 22.9 ms respectively, and AMP was of 49,4 + 31.7 uV. SIs were 0.93 + 0.04 for LN2, 0.92 + 0.06 for LP2 and 0.79 + 0.10 for AMP. This study demonstrated the possible use of LEPs for the assessment of the sensory auricular branch of facial nerve and gives the preliminary normative data for clinical use.