Purpose: The use of inferior alveolar nerve somatosensory evoked potentials may represent an objective means of evaluating sensory nerve function in the maxillofacial region. The aim of this work was to confirm the existence of a standard sequence of prominent events in the trigeminal somatosensory evoked potentials (TSEPs) of inferior alveolar nerve (IAN) waveform, examine those components and their normal variability by statistical analysis, and discuss TSEPs' nervous origin and some patterns of TSEPs' abnormalities due to dysfunctional nerves. Materials and Methods: TSEPs were obtained following electrical stimulation (square wave pulses 0.2 millisecond [ms] in duration, 4 to 6.5 mA, 0.7/second repetition rate, 200 averages) of the gum at the mental foramen level via intraoral surface electrodes and recorded from the contralateral central scalp sites. Results: We successfully recognized steady waveforms of sufficient quality and consistently recorded a "W"-shaped response: latency onset and peak of the initial deflection of positive polarity were approximately 12 ms and 20 ms, respectively. Negative and positive deflections followed with respective peak latencies at around 26 ms and 36 ms. One side of the lower lip can be compared with the contralateral side and patients may serve as their own control in cases of unilateral nerve injury. The anaesthetic block showed the total abolition of responses. Reproducible TSEP waveform was only obtained during nerve stimulation and not during masseter muscle stimulation. Conclusions: TSEPs, obtained with the present technique, may represent an objective, low-invasive, and reliable way of testing sensory nerve function in the maxillofacial region.
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