Key Concepts
Introduction
Bacterial meningitis is a life-threatening infection of the meninges (pia mater and arachnoid mater) and subarachnoid space, causing a robust inflammatory response that can lead to cerebral edema, increased intracranial pressure, cerebral infarction, and death within hours if untreated. Understanding the pathophysiology of blood-brain barrier (BBB) disruption and the inflammatory cascade is essential for nurses because it explains the urgency of antibiotic administration, the rationale for dexamethasone, and the expected CSF findings. The blood-brain barrier (BBB) is formed by specialized cerebral endothelial cells connected by tight junctions (occludin, claudin, ZO-1 proteins), surrounded by pericytes, and ensheathed by astrocyte end-feet. This barrier normally prevents circulating pathogens, immune cells, and large molecules from entering the CNS. Bacterial meningitis begins when pathogens breach this barrier through several mechanisms: (1) Hematogenous spread: bacteria in the bloodstream (bacteremia) attach to cerebral endothelial cells via surface adhesins, cross the endothelial layer via transcytosis or paracellular invasion, and enter the CSF. (2) Contiguous spread: from adjacent infected structures (sinusitis, otitis media, mastoiditis). (3) Direct inoculation: through skull fractures, neurosurgical procedures, or CSF shunts. Once bacteria enter the...