13th August 2020

An 18-month-old previously well boy, Jimmy, is brought to the GP surgery by his mother

An 18-month-old previously well boy, Jimmy, is brought to the GP surgery by his mother. She is concerned as Jimmy has dark rings around his eyes that look like bruising and have become more apparent over the past week. He also has a right drooping eyelid. She also reports that Jimmy doesn’t seem to recognise her face or her husband’s face. Jimmy has also been less active over the past month, seemingly too tired. His mother attributed this to having picked up a cold at nursery, as he had a runny nose recently. Jimmy was delivered vaginally at term with no complications. On examination, you confirm bilateral periorbital ecchymosis and right-sided ptosis. Jimmy blinks in response to light, but there is notable and persistent miosis of the right pupil, whereas the left pupil is responsive to light. A new onset Horner’s syndrome is suspected. 

What is the most likely cause of the Horner’s syndrome?

Select the SINGLE most appropriate option from the list below. Select ONE option only.