30th April 2024

A 45-year-old woman presents with a two-day history of high fever, severe headache, photophobia, and neck stiffness.

A 45-year-old woman presents with a two-day history of high fever, severe headache, photophobia, and neck stiffness. She has no significant past medical history and is not on any medications. On examination, she is febrile, has nuchal rigidity, and exhibits a positive Brudzinski’s sign.

Which investigation is most likely to confirm the diagnosis?