Review Question - QID 214691

A 47-year-old man presents to the emergency department complaining of “something stuck in his throat.” He states that shortly after eating a steak dinner, he felt a lump in the mid-sternal region that is worse with swallowing. He is able to swallow his secretions and tolerate solid and oral intake without issues. He took his father’s nitroglycerin without any symptomatic improvement. He denies any shortness of breath, weight loss, change in voice, or other neck masses. The patient reports many similar episodes in the past, but previous workup including an endoscopy 5 months ago did not yield any gross or pathological abnormalities. The patient has no other significant past medical history and takes no daily medications. His temperature is 98.6°F (37.0°C), blood pressure is 125/80 mmHg, pulse is 80/min, and respirations are 12/min. A physical examination is largely unremarkable and does not show any visible food bolus at the oropharynx. An electrocardiogram shows normal sinus rhythm without any ST-segment deviations. A subsequent barium swallow is obtained and is shown in Figure A. Which of the following is the most likely explanation for this patient’s symptoms?