Intraoperative nerve monitoring of marginal mandibular nerve during neck dissection

Marginal mandibular nerve injury is a complication that causes anaesthetic deficit that has a great impact on the patient’s perception ofappearance, inevitably influencing quality of life.1,2The reason forthis deficit is loss of innervation of depressor angulioris, depressor labii inferioris,mentalis, and orbicularis oris muscles, causing inability to move the lower lipdownward or laterally.3 The consequent cosmetic deficit, manifestinglower lip asymmetry and imbalance, is especially noticeable when opening themouth and is most obvious when the patient cries.2,4Because thecondition of the neck lymph nodes is the single most important prognosticfactor in carcinoma of the upper digestive airways, neck dissection has becomeordinary clinical practice in head and neck oncologic surgery.5

The main cause of nerve injury is that the marginal mandibular nerve hasa highly variable anatomy that cannot ensure reliable anatomic landmarks.

Nerve integrity monitoring (NIM) is a technique that monitors muscleactivity as a reflection of nerve function during surgery. The benefits ofelectromyographic monitoring for nerve preservation have been well establishedin many ear, nose, and throat (ENT) surgeries; however, its use is stilldebated in other procedures. The purpose of this study will be to assess theusefulness of NIM as an aid to reduce the incidence of marginal mandibularnerve paralysis after neck dissection, also to consider its possible impact oncosts and surgical time.

In our institution , among 74 patients with stage T1/T2 per primumcarcinoma tongue operated for per-oral wide local excision of tongue withunilateral neck dissection within January 2017 to June 2018, there is anincidence of around 58 % patients having temporary marginal paresis in the postoperative period and on follow up of minimum 3 months and more, around 32 % arestill having marginal nerve paresis i.e permanent nerve paresis