A patient undergoes a right total thyroidectomy. Postoperatively, the voice is hoarse and the right vocal cord is fixed in the paramedian position. The left vocal cord is normal. The most likely damaged nerve is the:

• A Right external branch of the superior laryngeal nerve
• B Right recurrent laryngeal nerve ✓
• C Right internal branch of the superior laryngeal nerve
• D Right vagus nerve (high cervical lesion)

Explanation

The recurrent laryngeal nerve (RLN) supplies all intrinsic laryngeal muscles except the cricothyroid and carries sensory fibres below the vocal cords. Unilateral RLN palsy causes the ipsilateral vocal cord to be fixed in the paramedian (adducted) position due to loss of abductor function (posterior cricoarytenoid) and adductor synergy, resulting in a weak, breathy, or hoarse voice. The external branch of the superior laryngeal nerve supplies only the cricothyroid muscle (pitch control); its damage causes a flat, monotonous voice without cord immobility. Internal branch SLN palsy causes laryngeal anaesthesia and aspiration but no cord palsy. High vagal lesion would also cause pharyngeal and palatal deficits.

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

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Written and medically reviewed by the StethoPrep medical team.