Clinical Reasoning: A teenager with persistent headache

A previously healthy 15-year-old boy with no relevant medical history presented with 3 weeks of severe, persistent, holocephalic pain associated with nausea and vomiting, without fever or alteration of consciousness. A brain MRI including magnetic resonance angiography and magnetic resonance venography (MRV) at a local hospital was normal. A lumbar puncture revealed a CSF pressure of 240 mm H2O. An intracranial infection was suspected based on clinical symptoms and signs. He received empiric antiviral therapy and rehydration for 1 week, but there was no relief of symptoms. He was subsequently transferred to our hospital.