Surgical Anatomy of the Marginal Mandibular Nerve: A Systematic Review and Meta‐Analysis

Abstract

The high number of marginal mandibular nerve (MMN) anatomical variants have a well‐known clinical significance due to the risk of nerve injury in several surgical procedures. The aim of this study was to find and systematize the available anatomical data concerning this nerve. The PubMed and Scopus databases were investigated in accordance with the Preferred Reporting Items for Systematic Reviews and Meta‐analyses guidelines. All studies reporting extractable data on the origin, course, splitting, anastomosis and relationship of the MMN with the mandible or the facial vessels were included. We included 28 studies analyzing 1861 halves. The MMN had one (PP = 35% 95% CI:18–54%), two (PP =35% 95% CI:18–54%), three (PP = 18% 95% CI:0–35%), or four branches (PP = 2% 95% CI:0–8%). Anastomosis with the great auricular nerve, transverse cervical nerve, mental nerve, and other branches of the facial nerve were defined. The origin of the MMN in relation to the parotid and the mandible was variable. The MMN nearly always crossed the anterior facial vein laterally (PP = 38% 95% CI:9–72% if single, PP = 57% 95% CI:22–90% when multiple); its relation with other vessels was less constant. At least one branch of the MMN was found below the inferior border of the mandible (IBM), with a PP of 39% (95% CI:30–50%). The MMN has high anatomical variability and it is more often represented by one or two branches; its origin is frequently described at the parotid apex and above the IBM, although in its course at least one branch often runs below the IBM. Its most frequent anastomosis is with the buccal branch of the facial nerve. Clin. Anat., 33:739–750, 2020. © 2019 Wiley Periodicals, Inc.

Marginal mandibular nerve — a wandering enigma and ways to tackle it

“…21). A systematic meta-analysis report by Marcuzzo et al [10] reported a prevalence of 30% for MMN originating at the parotid apex and 20% originating at the anterior border of the parotid and established the nerve location relative to the parotid gland. The results suggest that the nerve is above the parotid gland in 76% and below in 18% cases.…”

“…Further, Hazani et al [9] proposed that the MMN crosses above the facial artery at about one-fourth distance from the masseteric tuberosity up to mandibular midline and can be used as a reliable landmark for nerve localization. Meta-analysis by Marcuzzo et al [10] concluded that the MMN lies superficial to facial artery in 44% cases when the nerve has multiple branches and 36% cases when a single nerve branch is found. However, they emphasized that the relation to the anterior facial vein (AFV) is more constant and reliable as the nerve lies superficial to AFV in most cases.…”

High‐resolution ultrasound of the marginal mandibular branch of the facial nerve: Normal appearance and pathological findings in a postsurgical case series

“…It then steps over the mandible body and the most anteroinferior fibers of the masseter muscle and finally reaches the chin, where it distributes to the depressor anguli oris, depressor labii inferioris, and mentalis muscles (Figure 1(A)). Several connections between the MMN and regional nerves (e.g., greater auricular, transverse cervical, mental) or other divisions of the facial nerve may be encountered 14,15 …”

Anastomoses (Superficial Cervical Ansa) Between the Cervical Plexus and Peripheral Facial Nerve Branches: Implications for Regional Anesthesia in Carotid Endarterectomies – Anatomical Study

“…13 The marginal mandibular branch VII (MMB VII) runs along the inferior edge of the mandible, innervating the lower lip muscles (Figure 3). 1,14 These branches are partially cut during the initial skin incision. The quality of anesthesia in carotid endarterectomies could be potentially improved by blocking these nerves.…”

“…7,[10][11][12] Carotid endarterectomies typically involve painful surgical steps, including skin incision involving the dermatomes and the platysma (co-innervation by VII), vessel preparation (carotid plexus innervation: IX, X, ST), and potential retromandibular retractor insertion (co-innervation by V, VII). [7][8][9]13,14 The quality of anesthesia during skin incision is often decisive in regard to further patient comfort.…”