A 78-year-old man comes to the physician because of a change in his voice. His wife says his voice has progressively become higher pitched, and he has had a 5.4-kg (11.9-lb) weight loss over the past 4 months. He has smoked half a pack of cigarettes daily for the past 40 years. Direct laryngoscopy shows an irregular, nodular glottic mass. A biopsy specimen of the mass shows poorly differentiated squamous cells with nuclear atypia, hyperkeratosis, and disruption of the basement membrane. Involvement of a muscle derived from which of the following branchial arches is the most likely cause of his symptoms?
Answer D) 4th arch
Laryngeal carcinoma has caused this patient’s voice to become high-pitched. The pitch of the voice is heightened by contraction of the vocal cords. This function is carried out by the cricothyroid muscle.
The 4th branchial arch gives rise to the cricothyroid muscle as well as most muscles responsible for pharyngeal constriction.
Contraction of the cricothyroid muscle causes vocal cord contraction, which controls pitch elevation.
Involvement of the cricothyroid muscle should be suspected in any patient with changes in vocal pitch.