Positions of the implanted stimulating electrodes for artificial facial nerve for inducing contraction of the orbicularis oris muscle in rabbit with peripheral facial paralysis

Objective To explore the optimal positions of the implanted stimulating eletrodes for artificial facial nerve (AFN) for inducing contraction of the orbicularis oris muscle (OOM) in rabbit with peripheral facial paralysis. Methods According to the four microelectrodes of the AFN stimulating side, four modes of the implanted positions were divided. In line with different modes, the electrodes were implanted into the affected OOM of the rabbits with unilateral peripheral facial paralysis. AFN output electric stimulation to induce contraction of the affected OOM with uniform stimulating frequency and pulse length in vitro. Then compared the stimulus threshold amplitude and the peak amplitude separately among different modes by SAS 9.3 version statistical software. Results The differences of the stimulus threshold amplitude and the peak amplitude had no statistically significant separately between the first mode and the second mode (P>0.05), but there were statistically significant differences between the third mode and the fourth mode (P<0.05). Both kinds of the amplitudes were approximated between the first mode and the second mode respectively, and higher than those in the third mode or the fourth mode. Furthermore, both kinds of the amplitudes in the fourth mode were higher than those in the third mode. Conclusions The microelectrodes of the AFN stimulating lateral are implanted into the upper lip with a public microelectrode and an output microelectrode, into the lower lip with an output microelectrode, and into the way, which is located to the angle 40° to 45° about the line joining between the midpoint of the ipsilateral auricle root and the corner of the mouth with an output microelectrode. This is the third positional mode which requires lowest effective stimulus current intensity. Thus the mode is suitable as the optimal placement programme. Key words: Facial paralysis; Artificial facial nerve; Microelectrodes; Electric stimulation