Fungal aneurysms of intracranial vessels.

Intracranial fungal aneurysms arise from major cerebral arteries. Fungi directly invade vessel walls from the luminal surface (fungal emboli) or from the adventitia (fungal meningitis). The vasa vasorum are free of fungi. Aneurysmal rupture is common with extensive hemorrhagic necrosis of the surrounding brain. Aspergillus is the usual causative agent; its sources are nasal sinusitis or endocarditis.