What cranial nerve is responsible for sensation and taste on the lateral tongue?

Cranial Nerve Innervation of the Lateral Tongue

The facial nerve (CN VII) provides taste sensation to the anterior two-thirds of the tongue, while the trigeminal nerve (CN V) via its lingual branch provides general sensation to the lateral tongue.

Sensory Innervation of the Lateral Tongue

General Sensation

• The lingual nerve, a branch of the mandibular division (V3) of the trigeminal nerve (CN V), provides general sensory innervation (touch, pain, temperature) to the lateral tongue 1, 2
• This includes sensation to the anterior two-thirds of the tongue, lingual gingiva, and mucous membranes of the floor of the mouth 2

Taste Sensation

• The facial nerve (CN VII) carries special sensory fibers for taste sensation to the anterior two-thirds of the tongue 1, 3
• These taste fibers travel via the chorda tympani nerve (a branch of CN VII) which joins the lingual nerve to reach the tongue 3

Anatomical Pathway

1. Trigeminal Nerve (General Sensation)

   • Originates from the trigeminal ganglion
   • The mandibular division (V3) exits the cranium through the foramen ovale
   • The lingual branch travels to the tongue providing general sensation 4

2. Facial Nerve (Taste)

   • Taste fibers originate from the geniculate ganglion
   • Travel via the chorda tympani nerve
   • "Hitch-hike" with the lingual nerve to reach the tongue 3

Clinical Significance

• Damage to the lingual nerve can result in loss of general sensation to the lateral tongue 2, 3
• Injury to the chorda tympani branch of the facial nerve can cause loss of taste sensation to the anterior two-thirds of the tongue 1, 3
• Iatrogenic lingual nerve injury during mandibular third molar extraction is a significant risk due to the nerve's close proximity to the roots 3
• Posttraumatic neuropathy of the lingual nerve can be chronic and debilitating 5

Diagnostic Considerations

• MRI is the preferred imaging modality for evaluating the trigeminal nerve and its branches 1, 6
• High-resolution 3T MRI provides better anatomic resolution for visualizing these small nerve structures 6
• CT is useful for evaluating bony neurovascular foramina and canals through which these nerves pass 7

Important Distinctions

• The posterior third of the tongue receives both general sensation and taste from the glossopharyngeal nerve (CN IX) 1, 3
• The circumvallate papillae, located at the junction of the anterior two-thirds and posterior third of the tongue, are supplied by the glossopharyngeal nerve 3

Understanding this dual innervation pattern is essential for proper diagnosis and management of conditions affecting sensation and taste on the lateral tongue.