[Somatosensory evoked potentials in peripheral diseases of the facial nerve: a new investigation method].

In 1988, at the Facial Nerve Congress in Rio de Janeiro, results of facial nerve somatosensory evoked potentials (SEPs) by electrical stimulation of the Ramsay-Hunt zone were presented. In the clinical phase of this work, we have tested 8 normal subjects and 5 patients with unilateral peripheral facial palsy by the SEP method. Significant and reproducible responses were obtained in the normal nerves; general wave-form and different parameters are described: latency of different activities, differences inter and intra-subjects. In one case, we performed a brain mapping by stimulation of the Ramsay-Hunt zone to improve the localization of the different activities and to differentiate them from a possible auditory response to the electrical stimulation. In the pathological nerves, we observed significant changes in the morphology of the cortical waves with regards to the healthy nerves. Detailed results are presented in two cases with a long-term follow-up. We concluded that the electrical stimulation of the Ramsay Hunt zone evokes a cortical response like the electrical stimulation of other cutaneous zones. This response is significantly altered in peripheral facial palsy. Following studies should define the prognostic value of such modifications.