Viral Meningitis: An Overview
Viruses enter the brain by two major routes: hematogenous (carried by blood) or neural (carried by nerves). Most EV infections start in the intestine, after the individual swallows the initial inoculum, and spread to other tissues and the blood. Brain penetration is mediated by the hematogenous pathway. HSVs (HSV-1, HSV-2, VZV) enter the brain mainly via the peripheral and cranial nerves. Once inside the brain, the virus spreads through the subarachnoid space in cerebrospinal fluid (CSF), and its rapid replication can overcome the host defenses. Inflammatory WBCs such as lymphocytes accumulate and target the virus. Consequently, inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α are released. Inflammatory responses can increase the permeability of the blood-brain barrier, allowing the entrance of circulating immunoglobulins.
Pathogenesis
Viruses enter the brain by two major routes: hematogenous (carried by blood) or neural (carried by nerves). Most EV infections start in the intestine, after the individual swallows the initial inoculum, and spread to other tissues and the blood. Brain penetration is mediated by the hematogenous pathway. HSVs (HSV-1, HSV-2, VZV) enter the brain mainly via the peripheral and cranial nerves. Once inside the brain, the virus spreads through the subarachnoid space in cerebrospinal fluid (CSF), and its rapid replication can overcome the host defenses. Inflammatory WBCs such as lymphocytes accumulate and target the virus. Consequently, inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α are released. Inflammatory responses can increase the permeability of the blood-brain barrier, allowing the entrance of circulating immunoglobulins.
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