Anatomical features of the mastoid segment of the facial canal.

Background: Considering the tortuous course of the facial canal that houses the facial nerve, the stylomastoid artery and the homonymous vein, its morphological features are of great clinical significance in otologic, maxillofacial, oncologic, reconstructive and plastic surgery of the head and neck. The aim of this paper was to determine the individual specific features of the mastoid segment of facial canal and of the stylomastoid foramen.

Material and methods: The study was carried out on 82 temporal bones (41 right/41 left), at the Department of anatomy and clinical anatomy of Nicolae Testemitanu State University of Medicine and Pharmacy of the Republic of Moldova. The morphometry of the mastoid segment of the facial canal and of the stylomastoid foramen was performed. The morphometric parameters were statistically analyzed by descriptive and inferential statistics methods.

Results: The mastoid segment exited the facial canal by an obtuse, right and sharp angles, with a mean value of 113.1 ± 21.80° (right/left - 112.1 ± 23.85°/114.1 ± 19.76°), p = 0.701. The mean length of the mastoid segment was 15.1 ± 3.78 mm (right/left - 15.7 ± 3.66 mm/14.5 ± 3.84 mm), p = 0.153. The longitudinal diameter of the stylomastoid foramen had a mean of 3.0 ± 0.93 mm (right/left - 3.3 ± 0.96 mm/2.7 ± 0.81 mm), p = 0.007. The transverse diameter had a mean of 2.6 ± 0.74 mm (right/left - 2.9 ± 0.80 mm/2.4 ± 0.60 mm), p = 0.012.

Conclusions: In otologic surgery and particularly in mastoidectomy, it should be taken into consideration that the mastoid segment of the facial canal could exit the temporal bone by a sharp, right and obtuse angles that along with high morphological variability of the stylomastoid foramen might be a predisposal factor for Bell's palsy.