title: Somatosensory-evoked potential to evaluate the trigeminal nerve after sagittal split osteotomy.
abstract: OBJECTIVE
  The purpose of this study was to assess the onset period of trigeminal nerve hypoesthesia during bilateral sagittal split osteotomy, with the use of the trigeminal somatosensory-evoked potential (TSEP).
  
  
  METHODS
  Subjects were 10 patients with mandibular prognathism who underwent setback surgery. Intraoperative TSEP was measured 4 times: just before the commencement of the surgery, immediately after the induction of general anesthesia; after the medial periosteal dissection of the alveolar neurovascular bundle; after the sagittal split of bone; and after semirigid fixation with a titanium miniplate with the use of a monocortical screw. Postoperative TSEP was measured after the start of postoperative weeks 2, 4, 12, and 24. Normal records of the TSEP wave comprised peak (13 ms), trough (16 ms), peak (22.7 ms), and trough (36 ms) (N1, P1, N2, P2, respectively). Trigeminal hypoesthesia was assessed by the latency of P1 and N2, because they indicated the most reproducible waveforms.
  
  
  RESULTS
  The change in shape of the spectra indicated that prolonged latency was initiated on medial periosteal dissection and was extended further after the sagittal bone split and fixation. However, latency recovery was observed relatively quickly after the start of postoperative weeks 2 and 4.
  
  
  CONCLUSIONS
  Trigeminal hypoesthesia appeared to be induced by direct injury to the alveolar nerve during the bone split or by compression injury after fixation. Accordingly, the occurrence of a long-lasting postoperative trigeminal sensory hypoesthesia seemed to depend on nervous involvement of the split surface, the manner of fixation, or the intraoperative care.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kanazawa University School of Medicine, Kanazawa city, Japan. nakagawa@med.kanazawa-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Nakagawa
authors.forename: K
authors.initials: K
authors.lastname: Ueki
authors.forename: S
authors.initials: S
authors.lastname: Takatsuka
authors.forename: D
authors.initials: D
authors.lastname: Takazakura
authors.forename: E
authors.initials: E
authors.lastname: Yamamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000539:Alveolar Process / Q000294:innervation / Q000601:surgery; D001860:Bone Plates; D001863:Bone Screws; D004210:Dissection; D004568:Electrodiagnosis; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006987:Hypesthesia / Q000145:classification* / Q000209:etiology; D007430:Intraoperative Care; D008297:Male; D008334:Mandible / Q000601:surgery*; D008340:Mandibular Nerve / Q000503:physiopathology; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010027:Osteotomy / Q000009:adverse effects / Q000379:methods*; D010521:Periosteum / Q000601:surgery; D011378:Prognathism / Q000601:surgery; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D014025:Titanium; D014276:Trigeminal Nerve / Q000503:physiopathology*; D020433:Trigeminal Nerve Diseases / Q000145:classification* / Q000209:etiology
chemical_list: D014025:Titanium