A noninvasive technique has been developed for recording from the facial nerve within the fallopian canal. Following transcutaneous stimulation of the nerve on the face, an antidromic nerve potential can be detected with electrodes placed on the eardrum and enhanced by the technique of averaging. In studies conducted on cats and normal human subjects it has been determined that the primary recording site of the nerve potential is along the tympanic segment of the nerve just distal to the geniculate ganglion. Disturbances in nerve conduction caused by an experimental lesion produced changes in the recorded nerve potential. Thus it seems likely that this technique could assess a developing lesion in a patient with idiopathic facial nerve paralysis. A more accurate and earlier prognosis could be obtained than with conventional peripheral nerve testing techniques, since the severity of the developing lesion itself could be assessed.
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