Lingual nerve

Topography and course of the nerve

• Origin: Begins near the foramen ovale, at the same level as the inferior alveolar nerve.
• Interpterygoid space: Runs inferiorly and medially, passing between the lateral and medial pterygoid muscles. It lies within or deep to the interpterygoid fascia, anterior to the inferior alveolar nerve.
• Perimandibular region: Passes between the inner surface of the mandibular ramus and the medial pterygoid muscle.
• Sublingual region: Runs superior to the submandibular salivary gland on the superficial surface of the hyoglossus muscle. It then hooks around the submandibular duct inferiorly and laterally, branching into the lateral surface of the tongue.

Clinical note: In the region of the sublingual sulcus, the nerve lies very superficially.

Connection with the chorda tympani and autonomic ganglia

At the upper border of the medial pterygoid muscle, the chorda tympani (chorda tympani), which passes through the petrotympanic fissure, joins the lingual nerve. It contains fibers of the facial nerve:

• Taste fibers — to the taste buds of the anterior 2/3 of the tongue.
• Secretory parasympathetic fibers — to the submandibular and sublingual ganglia.

The lingual nerve is connected with the submandibular ganglion (gangl. submandibulare), and its branch, the sublingual nerve, with the sublingual ganglion (gangl. sublinguale). Postganglionic parasympathetic secretory fibers pass from the ganglia to the salivary glands.

Branches and zones of innervation

In the oral cavity, the following branches arise from the trunk:

• Branches of the fauces — to the mucous membrane of the fauces.
• Sublingual nerve (n. sublingualis) — to the sublingual region and sublingual salivary gland.
• Lingual branches — to the anterior 2/3 of the tongue and the lingual side of the mandibular gingiva.

Pathway of taste sensation

Afferent impulses from the taste buds of the anterior part of the tongue follow this pathway:

1. Travel within the lingual nerve.
2. Pass into the chorda tympani.
3. The cell bodies of the first sensory neurons are located in the geniculate ganglion (ganglion geniculi).
4. Proceed as part of the nervus intermedius to the brainstem and terminate in the nucleus of the solitary tract (nucleus tractus solitarii).

The fibers then cross and ascend to the thalamus within the medial lemniscus. Axons of thalamic neurons terminate in the lower part of the postcentral gyrus and the insula.

Clinical significance and anesthesia

The lingual nerve is typically blocked during anesthesia at the mandibular foramen and the lingula of mandible.

• Isolated anesthesia: Performed in the sublingual sulcus. The tongue is retracted with a spatula, and the injection is made into the mucosa at the level of the middle of the crown of the third mandibular molar. 2 ml of anesthetic is administered.
• Approach from the submandibular region: To block the lingual nerve, the needle is advanced upward along the inner surface of the mandibular ramus for another 1 cm after blocking the inferior alveolar nerve.
• Bershe–Dubov subzygomatic approach: The needle is advanced horizontally beneath the zygomatic arch toward the midline by 3–3.5 cm. The target area is located between the heads of the lateral pterygoid muscle, where the inferior alveolar and lingual nerves lie close together.
• Ageusia: Total loss of taste due to cranial nerve lesions is extremely rare, as taste fibers travel within three pairs of cranial nerves: CN VII, IX, and X.

Class and exam questions

What else to study on this topic

• Mandibular nerve (n. mandibularis)
• Chorda tympani (chorda tympani)
• Inferior alveolar nerve (n. alveolaris inferior)
• Topography of the interpterygoid space

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.