Intracranial microbial aneurysm (infectious aneurysm): current options for diagnosis and management

The histopathological characteristic of intracranial microbial aneurysm (MA)-infectious aneurysm is the presence of infection and destruction of the walls of the vessels. It can occur in the setting of predisposing infections that spread by endovascular mechanism (e.g., infective endocarditis) or extravascular mechanism (e.g., meningitis). MA is probably a better term than mycotic, infectious, or infective aneurysm as a wide variety of bacteria, fungi, mycobacteria, and virus can cause MA. Typically MAs are multiple, distal, and fusiform aneurysms, but the angiographic and clinical presentations can vary widely. The most common presentation of MA is intracranial bleed. CT angiography, MR angiography, or Digital subtraction angiography can be deployed to detect MA. By combining the clinical findings, imaging, and angiographic findings, it is possible to arrive at a correct diagnosis in most instances. MAs carry higher risk of rupture and fatal bleed when compared to other aneurysms. The treatment options include antimicrobial therapy, surgery, and endovascular therapy. The management strategy is based on large case series rather than controlled trials. All MA should receive appropriate antibiotic therapy. Ruptured MA with mass effect would require surgery in most situations, while those without mass effect and in non-eloquent locations could also be managed by endovascular therapy. Unruptured MA could be managed according to the size, location, and risk of bleeding-by antibiotic therapy, surgery, or endovascular therapy. Monitoring the resolution of the MA under antibiotic therapy by serial CT angiography is another option, but it carries higher risk of bleeding. Treatment of the underlying predisposing infection is an important component of therapy.