Retrospective Study of Facial Nerve Function Following Temporomandibular Joint Arthroplasty Using the Endaural Approach
Frederick Liu, DDS, MD
Eric J. Granquist DMD, MD
Purpose: The aim of this retrospective case control study is to evaluate the incidence of facial nerve injury associated with temporomandiblar joint (TMJ) arthroplasty using the endaural approach for the treatment of TMJ pathology.
Patients and Methods: The sample consisted of 36 consecutive patients who underwent TMJ arthroplasty. A total of 39 approaches were carried out through an endaural incision. Patients undergoing total joint replacement and/or with preexisting facial nerve dysfunction were excluded from the study. Four patients were lost to follow up and were excluded from the study. Facial nerve function of all patients was clinically evaluated by resident physicians preoperatively, postoperatively, and at follow up appointments. Facial nerve injury was determined to have occurred if the patient was unable to raise the eyebrow or wrinkle the forehead (temporalis branch), completely close the eyelids (zygomatic branch), or frown (marginal mandibular branch).
Results: 21 of the 36 patients or 22 of 39 approaches showed signs of facial nerve dysfunction following TMJ arthroplasty. This included 12 of 19 patients (12 of 21 approaches) who had undergone previous TMJ surgery. The most common facial nerve branch injured was the temporal branch, which was dysfunctional in all patients either as the only branch injured or in combination with other branches. By the 18th postoperative month, normal function had returned in 19 of 22 TMJ approaches. 3 of 22 TMJ approaches resulted in persistent signs of facial nerve weakness 6 months after surgery.
Conclusion: This epidemiological study revealed a low incidence of permanent facial nerve dysfunction. A high incidence of temporary facial nerve dysfunction was seen with TMJ arthroplasty using the endaural approach. The temporal branch of the facial nerve was most commonly affected, followed by 4 of 22 approaches (18.2%) with temporary zygomatic branch weakness. Having undergone previous TMJ surgery did not increase the incidence of facial nerve injury using the endaural approach. This information is important for patients and surgeons in the postoperative period, as a majority of patients will experience recovery of nerve function.