Trigeminal nerve hypesthesia after sagittal split osteotomy in setback cases: correlation of postoperative computed tomography and long-term trigeminal somatosensory evoked potentials.

PURPOSE: We sought to assess the relationship of the inferior alveolar nerve to the osteotomy site after bilateral sagittal split osteotomy (BSSO) and to correlate the nerve osteotomy relationship as the cause of long-term postoperative hypesthesia. PATIENTS AND METHODS: The subjects consisted of 28 patients with mandibular prognathism who underwent BSSO setback surgery. The distance between the ostectomized surface of the mandibular ramus and mandibular canal was measured and scored on a computed tomograph (CT). The relationship between this distance and the presence and degree or absence of trigeminal nerve hypesthesia was objectively evaluated by latency delay of the trigeminal somatosensory evoked potential (TSEP) records.
RESULTS: Five of the 56 sides (8.9%) showed latency delays more than 1 year after the operations. Scored CT points between the canal and the split surface strongly correlated with TSEP latency recovery (Y = 1.716X + 41.2).
CONCLUSIONS: This relationship between the canal and the osteotomy site is related to long-term hypesthesia in BSSO postoperatively.