Structure and Origin of the Lingual Nerve
- The lingual nerve arises from the posterior trunk of the mandibular nerve (CN V) within the infratemporal fossa.
- It courses deep to the lateral pterygoid muscle and superior to the tensor veli palatini muscle.
- The lingual nerve is joined by the chorda tympani and often by a communicating branch from the inferior alveolar nerve.
- It passes inferoanteriorly upon the medial pterygoid muscle towards the medial aspect of the ramus of the mandible.
- The lingual nerve crosses obliquely to the side of the tongue beneath the constrictor pharyngis superior and styloglossus.
- The lingual nerve runs from laterally to medially inferiorly, crossing the duct of the submandibular gland, and along the tongue to its tip becoming the sublingual nerve.

Course of the Lingual Nerve
- The lingual nerve courses deep to the lateral pterygoid muscle and superior to the tensor veli palatini muscle.
- It is joined by the chorda tympani and often by a communicating branch from the inferior alveolar nerve.
- The nerve passes inferoanteriorly upon the medial pterygoid muscle towards the medial aspect of the ramus of the mandible.
- It crosses obliquely to the side of the tongue beneath the constrictor pharyngis superior and styloglossus.

Distribution of the Lingual Nerve
General sensory:
- The lingual nerve supplies general somatic afferent (i.e. general sensory) innervation to the mucous membrane of the anterior two-thirds of the tongue.
- The posterior one-third of the tongue is innervated via the glossopharyngeal nerve (CN IX).
- The lingual nerve also supplies sensation to the floor of the oral cavity and the mandibular/inferior lingual gingiva.

Special sensory and parasympathetic autonomic:
- The lingual nerve conveys fibers of the chorda tympani, providing special sensation (taste) to the anterior two-thirds of the tongue.
- The chorda tympani fibers are derived from the facial nerve (CN VII).
- The lingual nerve also provides parasympathetic and sympathetic innervation.

Clinical Significance of Lingual Nerve Injuries
- The most common cause of lingual nerve injuries is third molar (wisdom tooth) surgery.
- Local anesthetic dental injections, particularly inferior dental block injections, can also injure the lingual nerve.
- Lingual nerve injuries can occur during sublingual or submandibular surgery.
- Sensory nerve injuries can result in pain, altered sensation, and/or numbness.
- Patients should be warned about the risk of lingual nerve injuries prior to surgery, such as wisdom tooth and floor of mouth surgery.

Additional Details about the Lingual Nerve
- The lingual nerve originates within the infratemporal fossa.
- It runs from laterally to medially inferiorly, crossing the duct of the submandibular gland, and along the tongue to its tip becoming the sublingual nerve.