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

Background: The growing number of parotid ablations, of reconstructive and cosmetic surgeries of the head and neck has considerably increased the risk of marginal mandibular branch (MMB) injury. Our study aimed to determine the anatomical peculiarities of the MMB in terms of 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 analysed.

Results: Seven FNBPs 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%); and Type NI (8%, non-identified types). In males, 1-3 MMBs were determined, while in females 1-4 MMBs; p = 0.845. In males, 1-3 MMBs were identified bilaterally. In females, on the right side, we found 1-2 MMBs and on the left - 1-4 MMBs; p = 0.204. A single MMB was revealed in 41 cases (54.7%), two MMBs - in 29 cases (38.7%), three MMBs - in four cases (5.3%), and in a single case, four MMBs (1.3%) were determined. Depending on the FNBP, the number of MMBs 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; and Type NI - 1.7 ± 0.82. Intergroup frequency variation (IGFV) = 1.403; degree of freedom (df) = 6; p = 0.226. According to the cephalometric type, the mean number of MMBs in the mesocephalic type (MCT) was 1.5 ± 0.68; in the brachycephalic type (BCT), it was 1.6 ± 0.52; and in the dolichocephalic type (DCT), it was 1.9 ± 0.60. IGFV = 1.698; df = 2; p = 0.190. A rare variant of 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 found to be characteristic of females, Type VI, and DCT. The lowest variation degree was found to be characteristic of Type I and MCT, without any gender differences. The risk of iatrogenic lesions of the MMB is conditioned by two important aspects: its anatomical variability and a large number of surgical interventions at that level.