Transection of the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery produces which specific deficit?

• A Loss of tension in the vocal cord (cricothyroid paralysis) with inability to produce high-pitched sounds ✓
• B Unilateral cord paralysis in the paramedian position causing hoarseness and aspiration
• C Loss of sensation above the vocal folds with risk of aspiration
• D Bilateral cord paralysis causing stridor requiring tracheostomy

Explanation

The external branch of the superior laryngeal nerve innervates the cricothyroid muscle, which elongates and tenses the vocal cord, producing high-frequency (high-pitched) sounds. This is the 'high note' muscle. Injury during thyroid or parathyroid surgery (it runs close to the superior thyroid artery) causes loss of voice pitch modulation — patients cannot sing high notes and have a weak, monotonous voice. Option B describes recurrent laryngeal nerve injury (which causes the typical unilateral cord palsy). Option C describes internal branch SLN injury (sensory above cords). Option D describes bilateral RLN injury.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.