Final answer:
The primary reason to have a patient letter 'e' during a CT exam of the larynx is to demonstrate vocal cord mobility.
Step-by-step explanation:
The primary reason to have a patient letter 'e' during a CT exam of the larynx is to demonstrate vocal cord mobility. The CT scan allows for detailed imaging of the larynx, including the movement of the vocal cords during speech and swallowing. This information is important for diagnosing disorders and evaluating the function of the larynx.