The exact cause of meningitis is often confirmed, but in many situations, bacteriologic diagnosis can be imperfect. Viral meningitis is usually uncomplicated and self-limited, so specific diagnosis is rarely necessary. The space between the pia and arachnoid is the subarachnoid space , in which CSF flows and medium-sized arteries supply the brain. Most CSF is produced in the choroid plexus of the ventricles, exits through foramina into the subarachnoid space, and is resorbed at the arachnoid granulations. Separate barriers are found between the circulation and the brain parenchyma, between the circulation and CSF, and between CSF and brain parenchyma.
Further protection occurs by the meningeal layers and skull.
Due to tight blood-brain barriers, CSF has little intrinsic defensive properties against infection. Tuberculous meningitis most commonly occurs from breakdown of subependymal or submeningeal granulomata , the result of previous seeding. Medical interventions such as placement of CSF shunts, neurosurgery, or lumbar puncture can cause meningitis by direct inoculation of external organisms. Antibiotic treatment leads to bacterial lysis, increased release of cell wall constituents, and increased cytokine levels. Bactericidal antibiotics in CSF to maximize sterilization and patient survival.