Oral and maxillofacial surgery and facial fractures: marginal mandibular nerve injury: practice question

A Dentistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Dentistry · Oral and maxillofacial surgery and facial fractures: marginal mandibular nerve injury

Sample item

After excision of the submandibular gland through an incision 2 cm below the angle of the mandible, the patient's lower lip corner droops when he smiles. Taste and tongue movements are normal. Which nerve was injured?

ALingual nerveBHypoglossal nerveCMarginal mandibular branch of the facial nerveDBuccal branch of the facial nerve

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Marginal mandibular branch of the facial nerve

The marginal mandibular branch runs just below the angle of the mandible and supplies the depressors of the lower lip. Injury leaves the lower lip unable to depress on that side, so the smile looks lopsided. The incision is placed low and the platysma and fascia are raised to protect it.

Option by option

A. Lingual nerve
Lingual nerve injury causes tongue numbness and taste loss, not lip droop.
B. Hypoglossal nerve
Hypoglossal injury causes tongue deviation and atrophy.
C. Marginal mandibular branch of the facial nerve (correct)
Correct. This branch controls depression of the lower lip and lies in the surgical field.
D. Buccal branch of the facial nerve
The buccal branch supplies the muscles of the cheek and upper lip.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Dentistry question

What is the answer to this Dentistry question?

The best answer is C, Marginal mandibular branch of the facial nerve. The marginal mandibular branch runs just below the angle of the mandible and supplies the depressors of the lower lip.

Why is "Lingual nerve" not the answer?

Lingual nerve injury causes tongue numbness and taste loss, not lip droop.

Why is "Hypoglossal nerve" not the answer?

Hypoglossal injury causes tongue deviation and atrophy.

Why is "Buccal branch of the facial nerve" not the answer?

The buccal branch supplies the muscles of the cheek and upper lip.

What concept does this question test?

It tests Oral and maxillofacial surgery and facial fractures: marginal mandibular nerve injury in Dentistry. Injury leaves the lower lip unable to depress on that side, so the smile looks lopsided. The incision is placed low and the platysma and fascia are raised to protect it.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Oral and maxillofacial surgery and facial fractures: marginal mandibular nerve injury?

Learn the dental formula, eruption ages and tooth structure once, as tables. Then use the flashcards and the other Dentistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.