Marginal mandibular branch of the facial nerve - anatomical peculiarities and clinical aspects.

Background: The expanding number of parotid ablations, reconstructive and aesthetic surgeries of the head and neck, considerably increased the risk of the marginal mandibular branch (MMB) injury. The purpose of our study was to determine the anatomical peculiarities of the MMB depending on the facial nerve branching pattern (FNBP), gender and cephalometric type.

Materials and methods: The MMB was dissected on 75 hemiheads of adult embalmed cadavers. The origin, number of branches, topography and connections of the MMB were analyzed.

Results: Seven FNBP were identified: Type I (18.7%); Type II (14.7%); Type III (20%); Type IV (14.6%); Type V (5.3%); Type VI (18.7%); Type NI (8%, non-identified types). In males 1-3 MMB were determined and in females 1-4 MMB; p = 0.845. In males, bilaterally were identified 1-3 MMB. In females on the right side were found 1-2 MMB and on the left - 1-4 MMB; p = 0.204. A single MMB was revealed in 41 cases (54.7%), 2 MMB - in 29 cases (38.7%), 3 MMB - in 4 cases (5.3%) and in a single case 4 MMB (1.3%) were determined. Depending on the FNBP, the number of the MMB was: Type I - 1.2 ± 0.43; Type II - 1.5 ± 0.52; Type III - 1.6 ± 0.63; Type IV - 1.5 ± 0.52; Type V - 1.3 ± 0.50; Type VI - 1.9 ± 0.95; Type NI - 1.7 ± 0.82. IGFV = 1.403 (intergroup frequency variation); df = 6 (degree of freedom); p = 0.226. According to the cephalometric type the number of the MMB in mesocephalic type (MCT) was 1.5 ± 0.68; in brachycephalic type (BCT) - 1.6 ± 0.52; in dolichocephalic type (DCT) - 1.9 ± 0.60. IGFV = 1.698; df = 2; p = 0.190. A rare variant of the MMB origin from the temporofacial division of the facial nerve was highlighted in 5.3% of cases.

Conclusions: The MMB varies depending on the FNBP, gender and cephalometric type. The highest variation degree was characteristic of females, Type VI and DCT. The lowest variation degree was determined in Type I and in MCT, without gender differences. The risk of iatrogenic lesions of the MMB is conditioned by two important aspects: its anatomical variability and large number of surgical interventions at that level.