Variations in Facial Nerve Branches and Anatomical Landmarks for Its Trunk Identification: A Pilot Cadaveric Study in the Lithuanian Population

Abstract

ObjectiveThe purpose of this study was to evaluate facial nerve (FN) branching variations based on Davis and Kopuz classifications in the Lithuanian population and measure the shortest distance from the facial nerve trunk (FNT) to its anatomical landmarks.MethodsTwenty-two hemifaces of 11 cadavers were dissected. The preauricular skin cut was made and extended behind the ear lobe and along the inferior border of the mandible. The skin with subcutaneous tissue and superficial fascia were separated and medially retracted, and the parotid gland was dissected anterogradely. The FNT and its furcation type and branching pattern were disclosed and noted based on Davis and Kopuz classifications. Further, the shortest distance from the FNT to the anatomical landmarks of the tragal pointer (TP), the angle of mandible (AM), and the tip of mastoid process (TMP) was measured.ResultsThe prevalence of branching patterns did not differ significantly compared to Davis classification. Based on Kopuz, type IVA pattern was the most common in six cases (27%). Eighteen (82%) trunks split as bifurcations and two (9%) trifurcations, while two (9%) had separate double trunks. The shortest distance (mm) from the FNT to the TP is 9.30 ± 0.93, AM 36.45 ± 4.14, and TMP 12.52 ± 2.30.ConclusionThe prevalence of FN variations in the Lithuanian population is similar to Davis classification. The AM and TMP are consistent superficial bony landmarks for trunk identification, while the distance from the TP highly varies among studies. Surgeons should be aware of double FNT during parotidectomy, which is described in Kopuz classification.

Transient immediate facial nerve paralysis after local anesthesia in a retro-auricular minor surgery

“…The literature reports several variants of the main trunk of the facial nerve by which the nerve may be split into 2 or even 3 trunks within the mastoid segment exiting through separate osseous foramina, or even more different variants on the same person from one side of the face compared to the other. 5 We suspect that our patient has a superficial variation of the facial nerve.…”

New classification of branching pattern of facial nerve during parotidectomy: A cross sectional study

“…Anatomy of FN was investigated previously in many studies [ 8 , [13] , [14] , [15] ] and different landmarks were studied by surgical and anatomical studies, for assistance of surgeons to safely recognize the FN, for instance, some authors stated that posterior belly of digastric muscle (DGM) is good reference landmark for recognition of FNT [ 16 ], while other investigators reported that styloid base and the posterior belly of DGM origin considered better and safe bone landmarks for the identification of FNT [ 17 ], as a consistent superficial bony landmarks, the mandible angle and the tip of mastoid process were considered by other studies to identify the trunk [ 18 ]. However, there is still much debate about the most reliable and safest landmarks.…”

“…However, there is still much debate about the most reliable and safest landmarks. Authors, proposed that the best landmark should be easily palpated and superficial in location which not need complete deep tissue resections [ 18 , 19 ].…”

“…Other researchers, Stankevicius et al and Pather et al, depend on measuring the distance between the FNT and angle of mandible, the mean distance was 36.45 ± 4.14 mm, and 38.10 ± 3.10 mm respectively [ 18 , 19 ]. While Stankevicius et al and Farahvash et al, measured the distance of FNT – TMP was found to be 12.52 ± 2.30 mm, and 11.81 ± 2.01 mm respectively [ 18 , 20 ], a mean of 9.30 ± 0.9 mm as reported for the FNT-TP-distance [ 18 ]. We didn't depend on this way of measurements because we think it's not practical for the surgeon to make this measurement in live patients as in cadavers.…”

“…Type II was persent in 15.22%, and was reported by one researcher only, he found in foetal specimens 12% of cases the facial nerve directly gives 5 terminal branches [ 21 ]. While it was described that FNT split as trifurcation in 9% [ 18 ] and Myint reported 3.8% trifurcation only [ 22 ]. Type III where there is separate double trunks of FN, constitutes 6.52% of our cases, while this type recognized by other researchers to constitute 8.57%,9%, 12% of the cases respectively [ 8 , 18 , 23 ].…”