Rapid Development and Rupture of an Infected Intracranial Aneurysm Caused by Streptococcus salivarius Meningitis: A...

The clinical manifestation of intracranial mycotic aneurysms (ICMAs), which are rare but carry high risks of rupture and early mortality, remains poorly understood. We present a case of an ICMA that rapidly developed and ruptured after the diagnosis of meningitis caused by Streptococcus salivarius (S. salivarius), which rarely causes bacterial meningitis. A 54-year-old man presented with a headache that worsened on coughing, without altered consciousness or vomiting. He was diagnosed with pneumocephalus due to a meningoencephalocele, which was detected on contrast-enhanced magnetic resonance imaging; no arterial abnormalities were identified. The day after admission, his headache worsened and the level of consciousness decreased. The cerebrospinal fluid analysis confirmed S. salivarius meningitis. On day 2, the patient suddenly became comatose. Head computed tomography revealed subarachnoid hemorrhage; the patient subsequently died. The autopsy revealed a ruptured 10 mm aneurysm in the right vertebral artery. ICMA is a rare but potentially fatal complication of bacterial meningitis. This case highlights the rapid progression of aneurysm formation during treatment, despite improvement of clinical symptoms and normal findings on initial imaging.