During which of the following procedures is the nerve supply to the muscles shown in the image most likely to be damaged?
A. Biopsy of a paratracheal lymph node
B. Dissection of the parathyroid glands
C. Excision of the superior pole of the thyroid gland
D. During surgical excision of a thyroglossal duct cyst
E. Tracheostomy
F. Excision of the lower parathyroid glands
Answer C
1. The cricothyroid muscles are innervated by the superior laryngeal branch of the vagus nerve. (it gives off the external branch of the superior laryngeal nerve)
2. The cricothyroid muscles tense the larynx during phonation. The muscles are attached to the anterolateral aspect of the cricoid and the inferior cornu and lower lamina of the thyroid cartilage. Their action causes the thyroid to tilt forward and tense the vocal cords.
3. The external branch of the superior laryngeal nerve is at risk for injury when undertaking surgery on the superior pole of the thyroid. It is here that the superior thyroid vessel is ligated and the nerve is very close by
4. Injury to the superior laryngeal nerve can result in voice fatigue, lowered voice fundamental frequency, lowered voice projection, and inability to achieve high-frequency sounds.
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