A 76-year-old woman presented to hospital by ambulance 45 min after developing sudden onset left face and arm weakness. She was taking methotrexate and prednisolone for rheumatoid arthritis. She had been unwell with fever and malaise for 3 days. On examination, her temperature was 39.1°C, pulse rate was 90 per minute and blood pressure 150/90 mm Hg. She was alert with no signs of meningism. There was a left-sided facial droop and left arm weakness. Chest and abdomen examinations were normal.

We assessed her on a treatment pathway for suspected stroke with a view to intravenous thrombolysis; her National Institute of Health stroke score was 5. Following CT scan of the head, we arranged a CT perfusion scan, which showed a small area of ‘mismatch’ in the right hemisphere adjacent to the lateral ventricle, consistent with an ischaemic penumbra (figure 1).

Our initial diagnosis was ischaemic stroke complicating systemic sepsis; the radiology seemed to support this. However, upon review, we felt that meningoencephalitis was more likely, given the prominent septic symptoms and the unusual location of the imaging abnormality. We, therefore, withheld intravenous thrombolysis …