Usual and Unusual Variations of Marginal Mandibular Branch of Facial Nerve – Nerve That Helps Symmetrical Smile

Background: Marginal mandibular branch of facial nerve , one of the motor terminal branches of facial nerve if injured inadvertently during different operative procedures in head & neck region, it produces neurodeficit as a – weakness of the lower lip muscles on the injured side. This study will increase our understanding about the anatomical details of this nerve in question, so that damage to this nerve during surgical intervention can be avoided. IN spite of considerable surgical importance, there are not many studies on Marginal Mandibular Nerve particularly from this zone of India which drives the present researcher to pursue this cadaver based study on Marginal Mandibular Nerve, one of the terminal branches of Facial Nerve with respect to its course relations and communication. Aim: The aim of the present study is to provide information regarding the number of branches of Marginal Mandibular Branch of Facial Nerve (MMBFN), relation of these branches to the facial vessels, communication between branches of MMBFN with other branches of Facial nerve and its relation to lower border of the body of the mandible. This knowledge will definitely help the surgeons performing Parotidectomy, Carotid end- arterectomy, Submandibular gland excision, Deep dissection of neck, Mandibular advancement surgery etc. Materials and Methods: A Cross-sectional observational study was conducted in Nil Ratan Sircar Medical College Kolkata, West Bengal within 2021 to 2023 after Institutional Ethical clearance. In this study 50 halves of faces of embalmed cadavers of both sexes were dissected & analysed. Number of branches, course & relation with facial vessels, relation with lower border of mandible & to deep fascia and communications of MMBFN if any was noted after meticulous dissection. All the variables collected for statistical analysis were then evaluated by SPSS 20.0.1 Results: In the present study, MMBFN was represented by Single branch in 42 (84%) cases, exhibit two rami in 14% cases and as three rami in 2% cases. 55(93.2%) out of 59 rami of MMBFN , crossed facial vessels externally and in 4(6.8%) branches, the MMBFN divided into two branches and reuniting again to form a single nerve trunk. The loop so formed enclosed facial artery. 20.3% of MMBFN passed above the inferior border of mandible,45.8% along the inferior border of mandible and 33.9% passed below the inferior border of mandible. Communication between the main or subsidiary branches of MMBFN was present in 10