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.