Studies on the Sensory Nerve Action Potentials of Lingual Nerve
Lingual nerve (LN) injury is common trauma disease in the field of oral surgery such as an iantrogenic injury during the third molar extration. The early diagnose and proper treatment lead to good convalescence for nerve regeneration. In order to identify the symptoms associated with LN injury, and the subjective symptoms such as the sensory tests were recorded. In addition, the 2-point discrimination, pain and temperature tests and the SW (Semmes Weinstein pressure) esthesiometer which performs a tactile threshold test (SW test) were used. In case of inferior alveolar nerve (IAN), it is generally possible to diagnose by using X-ray and CT that can which easily to image a mandibular canal damage. However LN injury is difficult to be diagnosed the degree of damage because it is surrounded by soft tissue. Our recently study proved a sensory nerve action potential (SNAP) is usefulness for the diagnosis of IAN injury. The object of this study is to establish diagnosis of LN nerve injury by using SNAP.
Materials and methods
Twenty healthy volunteers participated in this study in which LN was stimulated with 2 needle electrodes. The nerve-stimulating electrode was stabled in border of the tongue section and the recording electrode was stabled near the mandibular foramen. Constant current stimulations of square waves were applied at supramaximal stimulus for durations of 0.1msec and frequency of 1c.p.s. The information was recorded by orthodromic method and averaged over 30 trials and SNAP were derived. We calculated the maximum sensory nerve conduction velocity (SNCV) the latency and the size of the waveform.
Results
The average of latency was 0.909ms, the mean was 0.77ms. The average of the stimulus strength was 0.92mA. Average conduction distance was 48.3mm. The average maximum SNCV in 52.76m/s, the fasetest was 59.0m/s.
Conclusions
In case of IAN, mandibular foramen and mental foramen is an anatomical structure, which is an indicator of the stimulation and recording electrode insertion site position. However, LN does not have definite structure to be characterized because it is surrounded by the soft tissue. In all 20 subjects, it was possible to record a waveform. Disturbance of the waveform decreased by pulling and settling the tongue. This leads us to our point that determining LN SNAP in clinical settings would be an effective method to understand the degree of nerve injuries.