Inferior Alveolar Nerve Injury — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Inferior Alveolar Nerve InjuryMFDS Part 1

A 25-year-old patient develops unilateral numbness of the lower lip and chin, together with reduced sensation in the mandibular teeth, following a bilateral sagittal split osteotomy. Sensation and taste in the tongue are normal. Which nerve was most likely injured?

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Correct answer: B — Inferior alveolar nerve

The inferior alveolar nerve is most likely injured. It traverses the mandibular canal and is vulnerable during sagittal split osteotomy. A proximal injury affects sensation from the mandibular teeth and, through its terminal mental branch, the lower lip and chin. An isolated mental nerve injury could produce lower-lip and chin numbness but would not account for altered sensation in the mandibular teeth. Lingual nerve injury causes altered general sensation and potentially taste in the anterior tongue. The buccal nerve supplies the cheek and buccal gingiva, while the mylohyoid nerve is predominantly motor to mylohyoid and the anterior belly of digastric.

Reference: Royal College of Surgeons of England. Commissioning guide: Orthognathic procedures, section 4(a), 2013. https://www.rcseng.ac.uk/-/media/files/rcs/standards-and-research/commissioning/orthognathic-procedures_published.pdf