Anatomy & Histology · patient case question
Which nerve carries TASTE from the posterior one-third of the tongue?
Patient case: A lesion on the side of the tongue
Patient: Male, 63 years old
Chief Complaint: “There is a rough patch on the side of my tongue.”
Background: Forty pack-year smoking history, daily alcohol. No prior oral lesions.
Findings: A 1.5 cm indurated white and red lesion on the posterior lateral border of the tongue on the left. Incisional biopsy performed under local anaesthesia. At review the patient reports altered taste and reduced sensation over the area.
Show answer and explanation
Correct answer: B. Glossopharyngeal nerve (CN IX)
- A. The chorda tympani carries taste from the ANTERIOR two-thirds. It is a branch of CN VII that hitches a ride with the lingual nerve.
- B. CORRECT. The GLOSSOPHARYNGEAL nerve carries BOTH taste and general sensation from the posterior one-third of the tongue — it is the one region where a single nerve does both jobs. This matters for a posterior lateral lesion: infiltration at its base can produce taste loss as well as numbness.
- C. The hypoglossal nerve is purely motor to the intrinsic and most extrinsic tongue muscles, with no sensory or gustatory function.
- D. The lingual nerve carries GENERAL sensation — touch, temperature, pain — from the anterior two-thirds, but not taste from that region; it merely conveys the chorda tympani fibres.
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