Purpose: The purpose of this radiologic study was to determine the precise location of the temporal branch of the facial nerve in relation to the most anterior aspect of the bony external acoustic canal without distortion of the position of the nerve by surgical manipulation or cadaveric fixation artifact.
Materials and methods: This was a retrospective study of 30 patients with a mean age of 38 years (range, 22 to 67 years) with no history of previous surgery or trauma. Thirty axial high-resolution magnetic resonance imaging examinations at the level of the zygomatic arch were examined to determine the location of the temporal branch. The nerve was identified by following its course from the stylomastoid foramen to an area lateral to the frontozygomatic suture. Three individuals made 3 measurements of each image with digimatic calipers. The high and low values were discarded, and the remaining 3 values were analyzed. These examiners were trained in locating the nerve and bony landmarks and were tested for accuracy in measurement. No inter- or intraoperative variability was noted.
Results: The mean distance of the most posterior ramus of the temporal branch of the facial nerve to the most anterior aspect of the external acoustic canal was 2.12 cm +/- 0.21 cm (range, 1.68 to 2.49 cm). The course of the temporal branch was easily identified, and the examiners were consistent in their measurements. In all cases examined, there was no evidence of facial trauma or other facial surgery in the patient histories. All nerves were found superficial to the zygomatic arch, just deep to the superficial musculoaponeurotic system, or the temporozygomatic fascia, which is the connective tissue layer just deep to the subcutaneous fat.
Conclusion: The temporal branch of the facial nerve is at risk for injury during a variety of facial surgical procedures because of its location. This study found the nerve to be in a slightly less vulnerable position during a preauricular approach than Al-Kayat and Bramley's classic study (0.8-3.5 cm), and also established a narrower range of nerve position variability.