Correct Answer: C. Lingual nerve
The lingual nerve is the most frequently injured nerve during submandibular gland resection due to its intimate anatomical relationship with the gland. The lingual nerve runs medial to the submandibular gland, passing through the hilum and lying in close proximity to the gland's capsule and ducts. During surgical dissection and removal of the gland, the nerve is at highest risk of injury because it cannot be easily separated from the gland tissue without careful identification and retraction. Injury to the lingual nerve results in loss of taste sensation (anterior two-thirds of tongue via chorda tympani fibres) and sensory loss over the anterior two-thirds of the tongue on the affected side. This is a well-recognized complication of submandibular gland surgery, occurring in 20–70% of cases depending on surgical technique. The hypoglossal nerve, while nearby, runs more superficially and laterally, making it less vulnerable. The inferior alveolar nerve and nerve to mylohyoid are branches of the mandibular division of the trigeminal nerve and lie deeper in the surgical field, away from the direct dissection plane of the gland.
Why the other options are wrong
A. Hypoglossal nerve — The hypoglossal nerve runs more superficially and laterally to the submandibular gland, passing over the external carotid artery. While it is in the operative field, it is not intimately related to the gland itself and can be identified and preserved more easily during standard surgical dissection. Injury is less common than lingual nerve injury. B. Inferior alveolar nerve — The inferior alveolar nerve is a branch of the mandibular division of V3 and runs deeper in the surgical field, passing through the mandibular foramen. It is not directly related to the submandibular gland dissection plane and lies outside the typical surgical exposure for gland resection. Injury to this nerve is rare during submandibular gland surgery. D. Nerve to mylohyoid — The nerve to mylohyoid is a small branch of the inferior alveolar nerve that supplies the mylohyoid muscle and anterior belly of the digastric. It lies deep to the mandible and is not in the direct dissection plane of the submandibular gland. It is rarely injured during standard submandibular gland resection.
High-Yield Facts
- Lingual nerve injury is the most common nerve complication of submandibular gland resection (20–70% incidence), causing loss of taste and sensation over anterior two-thirds of tongue.
- The lingual nerve runs medial to the submandibular gland, passing through the hilum and lying in the gland's capsule, making it vulnerable during dissection.
- Chorda tympani fibres (taste to anterior two-thirds of tongue) travel with the lingual nerve and are lost with lingual nerve injury.
- Hypoglossal nerve injury causes ipsilateral tongue paralysis and atrophy but is less common than lingual nerve injury because it runs more superficially and laterally.
- Inferior alveolar and mylohyoid nerves lie deeper in the surgical field away from the submandibular gland dissection plane and are rarely injured.
Mnemonics
LINGUAL = Lateral to gland hilum (medial in anatomy, but lateral to main dissection) Remember: Lingual nerve is Lost most often in submandibular gland surgery because it runs Medial to gland and through the Hilum — closest to dissection plane. Use when recalling which nerve is at risk in submandibular surgery. HIM nerves (Hypoglossal, Inferior alveolar, Mylohyoid) — safer in submandibular surgery Hypoglossal runs superficially/laterally, Inferior alveolar runs deep through mandible, Mylohyoid is a small deep branch. None are intimately related to gland hilum like lingual nerve. Use to eliminate wrong options quickly.
NBE Trap
NBE may pair submandibular gland surgery with hypoglossal nerve injury (a common misconception because hypoglossal nerve is nearby and controls tongue motor function), but lingual nerve is actually the most frequently injured because of its intimate relationship with the gland hilum and capsule.
Clinical Pearl
In Indian tertiary centres, submandibular gland resection for malignancy (often squamous cell carcinoma in tobacco users) is a common procedure. Postoperative lingual nerve injury manifests as loss of taste sensation and numbness of the anterior tongue — patients often complain of altered taste perception and difficulty with food sensation, which impacts quality of life. Careful nerve identification and gentle retraction during surgery are critical to minimize this complication.
_Reference: Bailey & Love's Short Practice of Surgery, Ch. 38 (Salivary Glands); Robbins & Cotran Pathologic Basis of Disease, Ch. 16 (Head and Neck)_