During surgery involving the SUBMANDIBULAR gland, which nerve is at greatest risk of injury?

Correct answer: C. The lingual nerve

• A. The facial nerve TRUNK exits the stylomastoid foramen and lies within the parotid — at risk in parotid surgery. In submandibular surgery the branch at risk is the MARGINAL MANDIBULAR branch, which runs superficially above the gland and whose injury causes lower-lip weakness; the trunk itself is not encountered.
• B. The mylohyoid nerve, a motor branch of the inferior alveolar nerve, supplies the mylohyoid and anterior digastric. It may be encountered but its injury is functionally minor compared with lingual nerve damage.
• C. CORRECT. The LINGUAL NERVE is intimately related to the submandibular gland and duct. It runs on the lateral surface of the tongue, passes BENEATH the submandibular duct as it crosses from lateral to medial, and carries the parasympathetic secretomotor fibres to the gland via the submandibular ganglion, which is suspended from it. Injury produces loss of general sensation and TASTE (through the chorda tympani fibres travelling with it) over the anterior two-thirds of the ipsilateral tongue.
• D. The buccal (long buccal) nerve supplies the buccal mucosa and skin of the cheek and lies well anterior and superficial to the submandibular region.

Note: Memory hook for the duct–nerve relationship: the lingual nerve takes a DOUBLE CURVE around Wharton's duct, passing lateral, then inferior, then medial to it. The old aphorism is that the lingual nerve, like a lover, 'goes under the duct twice'.