Clinically relevant landmarks of the frontotemporal branch of the facial nerve: a three-dimensional study.

ABSTRACT

The frontotemporal branch of the facial nerve (FTN) is vulnerable during craniofacial surgeries due to its superficial course and variable distribution. Surface landmarks that correlate with the underlying course of the FTN can assist in surgical planning. Estimates of the course of FTN commonly rely on Pitanguy's line (PL), which utilizes variable soft-tissue landmarks. The purpose of this study was to evaluate palpable surface landmarks to predict the course and distribution of FTN using 3D modeling. Fifteen half-heads were used. In five formalin-embalmed specimens, surface topography was obtained using a FARO® scanner and landmarks corresponding to PL, porion, supraorbital notch, frontozygomatic and zygomaticotemporal sutures, and supraorbitomeatal line (SOML) and infraorbitomeatal line (IOML) were demarcated/digitized using a Microscribe™ digitizer. A preauricular flap was raised, and branches of FTN were isolated and digitized. The data were reconstructed into 3D models (Geomagic®/Maya®) to quantify landmarks. In 10 Thiel-embalmed specimens, four independent raters identified/palpated and pinned the frontozygomatic and zygomaticotemporal sutures and PL. Data were collected and analyzed using the same protocol as in the first part of the study. Landmarking of PL was inconsistent between raters and not representative of FTN distribution. The easily identifiable surface landmarks defined in this study, a line 12 mm anterior to the porion along the SOML and IOML and a line joining the zygomaticotemporal and frontozygomatic sutures, comprehensively captured the distribution of FTN. The raters found a mean of 21 ± 2 branches between the lines out of a total of 22 ± 2 branches. These landmarks may be used clinically to avoid injury to FTN.