19th February 2024

A 67-year-old smoker presented to the acute medical unit with ptosis.

A 67-year-old smoker presented to the acute medical unit with ptosis. Miosis is noted on examination, and she has not noticed any sweat along the right side of her face, only while in a hot environment. She also notes pain along her right arm and a persistent cough and haemoptysis over the past six months. A CXR shows the presence of an apical lung tumour. 

Given the clinical findings, what is the likely cause for the patient’s Horner’s syndrome?