An Anatomical study for localisation of Zygomatic branch of Facial nerve and Masseteric nerve - An aid to nerve coaptation for facial reanimation surgery: A cadaver based study in Eastern India

Abstract

Context: In cases of chronic facial palsy, where direct neurotisation is possible, ipsilateral masseteric nerve is a very suitable motor donor. We have tried to specifically locate the masseteric nerve for this purpose.

Aims: Describing an approach of localisation and exposure of both the zygomatic branch of Facial nerve and the nerve to masseter, with respect to a soft tissue reference point over face.

Settings and design: Observational cross sectional study, conducted on 12 fresh cadavers.

Subjects and methods: A curved incision was given, passing about 0.5cms in front of the tragal cartilage. A reference point "R" was pointed out. The zygomatic branch of facial nerve and masseteric nerve were dissected out and their specific locations were recorded from fixed reference points with help of copper wire and slide callipers.

Statistical analysis used: Central Tendency measurements and Unpaired "t" test.

Results: Zygomatic branch of the Facial nerve was located within a small circular area of radius 1 cm, the centre of which lies at a distance of 1.1 cms (±0.4cm) in males and 0.2cm (±0.1cm) in females from the point, 'R', in a vertical (coronal) plane. The nerve to masseter was noted to lie within a circular area of 1 cm radius, the centre of which was at a distance of 2.5cms (±0.4cm) and 1.7cms (±0.2cm) from R, in male and female cadavers, respectively. Finally, Masseteric nerve's depth, from the masseteric surface was found to be 1cm (±0.1cm; male) and 0.8cm (±0.1cm; female).

Conclusions: This novel approach can reduce the post operative cosmetic morbidity and per-operative complications of facial reanimation surgery.

Keywords: Chronic facial palsy; masseteric nerve; zygomatic branch (of facial nerve).

Figure 1

Schematic curved preauricular incision (yellow line) - edited with Microsoft Paint on primary internet source picture. Variations of the facial nerve (cranial nerve VII), shown in situ, in 2 numbered illustrations. Superficial dissection of the head and face to show nerves. Lateral views. https://www.pinterest.com/pin/379428337327818673

Figure 2

Skin incision (curved preauricular)

Figure 3

Reference point (r) (yellow) - edited with Microsoft Paint on primary internet source picture. Variations of the facial nerve (cranial nerve VII), shown in situ, in 2 numbered illustrations. Superficial dissection of the head and face to show nerves. Lateral views. https://www.pinterest.com/pin/379428337327818673

Figure 4

Schematic guidance to localisation of nerve to masseter and zygomatic branch of facial nerve. Edited with Microsoft Paint on primary internet source picture. https://www.pinterest.com/pin/554576141589972856

Figure 5

Operating Window for localisation of the concerned nerves (showed by yellow circle); superficial fibres of the masseter muscle are reflected forwards

Figure 6

Predisposition of masseteric nerve and zygomatic branch of Facial nerve – a scope for tension free coaptation A – Tendon of masseter muscle M – Masseteric nerve Z – Zygomatic branch of Facial nerve T – Temporal branch of facial nerve

Figure 7

Gender-based comparison of depth of masseteric nerve. (Created with Microsoft Office Excel 2007)

Figure 8

Gender-wise comparison of the locations of zygomatic branch of facial nerve and masseteric nerve in transverse and coronal planes. (Created with Microsoft Office Excel 2007)