Fatal pneumocephalus caused by Clostridium perfringens bacteremia originating from emphysematous cystitis after stroke-related blood-brain barrier disruption.

Infectious pneumocephalus is rare and usually associated with meningitis or neurosurgical procedures. We report a fatal case of diffuse pneumocephalus caused by Clostridium perfringens bacteremia originating from emphysematous cystitis in a patient recently admitted for a large right middle cerebral artery infarction. Imaging demonstrated subarachnoid gas strictly confined to the infarcted hemisphere, followed by subdural air accumulation and fatal mass effect. We hypothesize that stroke-related blood-brain barrier disruption permitted hematogenous bacterial and gas diffusion into the subarachnoid space. This case highlights the distinction between negative-pressure postoperative pneumocephalus and positive-pressure infectious pneumocephalus in a closed skull.