Waveform reliability with different recording electrode placement in facial electroneuronography

Electroneuronography (ENoG) has become a useful test for estimating the degree of facial nerve degeneration and predicting the prognosis in patients with facial nerve palsy. Test results may be influenced by several factors, including the electrode positions, skin resistance, stimulus magnitude, and possible artifacts. Regarding recording electrode positions, different groups have used two different locations, the nasolabial fold and nasal ala. The authors compared the waveforms recorded from these two locations in ENoG recordings to obtain the optimal waveform. Twenty healthy volunteers and 25 patients with unilateral facial nerve palsy were included in this study. Recordings were carried out with the recording electrode placed on the nasolabial fold, followed by placement on the nasal ala after 10 minutes. The following parameters were assessed: (1) the supramaximal threshold, (2) amplitude and shape of the waveform, (3) interside difference, and (4) test-retest variability. There was no significant difference in the amplitude of the waveform, interside difference, and test-retest variability between the two groups. However, when the electrode was placed on the nasal ala, the threshold was significantly lower, an ideal biphasic configuration was present in almost all cases (97.5 per cent) of normal volunteers and it was easier to identify the waveform. Placement of the recording electrode on the nasal ala would be the preferred method.