system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 60-year-old man comes to the physician because his wife has noticed that his left eye looks smaller than his right. He has had worsening left shoulder and arm pain for 3 months. He has smoked two packs of cigarettes daily for 35 years. Examination shows left-sided ptosis. The pupils are unequal but reactive to light; when measured in dim light, the left pupil is 3 mm and the right pupil is 5 mm. Which of the following is the most likely cause of this patient's ophthalmologic symptoms?
assistant
Compression of the stellate ganglion