19th February 2024

A 43-year-old female with known cervical cancer was admitted to the hospital with a gradually worsening headache.

A 43-year-old female with known cervical cancer was admitted to the hospital with a gradually worsening headache. This was associated with occasional fevers. She developed double vision and photophobia this morning. She denies any neck stiffness. 

Examination reveals periorbital oedema and chemosis bilaterally. Reduced range of movement of her eye was noted in all directions, and she reports pain in eye movement. Her right pupil was normal, but her left pupil was constricted and unreactive to light. Her visual acuity remained intact. Her CT brain was unremarkable.

Given the likely diagnosis, which of the following structures has been affected?