Evaluation of Lower Lip Hypoesthesia Using Trigeminal Somatosensory Evoked Potential After Sagittal Split Ramus Osteotomy: Retrospective Study

Objective: This study evaluated the degree of paresthesia and recovery of the lower lip and chin in patients who underwent sagittal split ramus osteotomy (SSRO) by measuring the preoperative and postoperative trigeminal somatosensory evoked potential (TSEP).

Study design: Thirty-seven patients with skeletal class II and III malocclusion who underwent SSRO were included. TSEP was measured at 7 points: preoperatively and 1 week, 1, 3, 6, 12, and 18 months postoperatively. The Semmes-Weinstein monofilament test (SW test) was also performed concurrently.

Results: Patients were considered to have recovered when the preoperative values were achieved postoperatively. Stimulation and latency N25 showed significant positive correlations with the SW test. Stimulation measured using TSEP was significantly lower than that measured in the SW test at each time point (P<0.001). In contrast, latency N25 measured using TSEP was significantly higher than that measured in the SW test (P<0.001). TSEP measurements indicated earlier remission compared with the SW test (P<0.001).

Conclusion: The gap between qualitative and quantitative evaluations was indicated. Therefore, TSEP may be a more sensitive alternative for evaluating trigeminal nerve paresthesia after orthognathic surgery. Furthermore, it enables a detailed analysis of the degree of nerve recovery.