A 26-year-old woman is evaluated for increasing discomfort in the right posterior mandible. The patient has no prior medical conditions and takes no medications. Physical examination is unremarkable with the exception of a partially erupted right mandibular third molar tooth. Radiographs reveal impaction of the molar tooth. Surgical tooth extraction under general anesthesia is performed. During the surgery, the inferior alveolar nerve that is close to the tooth is inadvertently injured. Which of the following is the most likely to be observed on the injured side?

Question

A 26-year-old woman is evaluated for increasing discomfort in the right posterior mandible.  The patient has no prior medical conditions and takes no medications.  Physical examination is unremarkable with the exception of a partially erupted right mandibular third molar tooth.  Radiographs reveal impaction of the molar tooth.  Surgical tooth extraction under general anesthesia is performed.  During the surgery, the inferior alveolar nerve that is close to the tooth is inadvertently injured.  Which of the following is the most likely to be observed on the injured side?

Quizplus · Accepted Answer

11ec160b_35a8_a9eb_9249_9176ddfcb612_MD0001_00 The inferior alveolar nerve is a branch of the mandibular nerve (CN V3). After branching from CN V3, it enters the mandibular foramen to travel within the mandibular canal, where it can be vulnerable to iatrogenic injury during dental procedures. From inside the mandibular canal, it gives off small branches to provide sensory innervation to each of the lower teeth. The inferior alveolar nerve also gives off the mental nerve, which exits the mandibular canal through the mental foramen. The mental nerve conveys sensory information from the chin and lower lip (both skin and mucosal surfaces). Therefore, iatrogenic injury to the inferior alveolar nerve often results in unilateral numbness of the lower teeth, chin, and lower lip. Nerve blocks can be performed at the mandibular foramen to provide anesthesia for dental procedures or at the mental foramen to facilitate laceration repair of the chin and lower lip. (Choice A) General sensation in the anterior tongue is carried by the lingual nerve. It is also a branch of CN V3, but it arises proximal to the inferior alveolar nerve branch. It passes between the medial pterygoid muscle and the ramus of the mandible (not into it), then through the floor of mouth where it crosses (and can be injured in procedures involving) the submandibular gland duct. (Choices B and E) Both general and taste sensation in the posterior tongue are carried by the glossopharyngeal nerve (CN IX). (Choice D) Taste sensation in the anterior tongue is mediated by the chorda tympani nerve, a branch of the facial nerve (CN VII) that travels with the lingual nerve. (Choice F) The masseter muscle is innervated by the masseteric branch of the anterior division of the mandibular nerve (CN V3). This arises from CN V3 proximal to the branching of the inferior alveolar nerve. Educational objective: The inferior alveolar nerve travels within the mandibular canal to provide sensation to the lower teeth and can be injured during dental procedures. It gives off the mental nerve, which exits through the mental foramen to provide sensation to the chin and lower lip.

A 26-Year-Old Woman Is Evaluated for Increasing Discomfort in the Right