Meningitis, encephalitis
1. Big picture
Meningitis and encephalitis are medical emergencies. The key exam skill is to recognize the syndrome quickly, take cultures and cerebrospinal fluid (CSF) safely, and start empirical treatment without dangerous delay.
Core distinction:
| Syndrome | Main site of inflammation | Dominant clinical clue |
|---|---|---|
| Meningitis | Meninges and subarachnoid space | Fever + headache + neck stiffness ± altered mental status |
| Encephalitis | Brain parenchyma | Fever + altered consciousness/personality change + seizures/focal neurological signs |
| Meningoencephalitis | Both meninges and brain | Meningeal signs plus encephalitic features |
The most dangerous exam pattern is:
Fever + headache + neck stiffness or confusion → take blood cultures, perform lumbar puncture if safe, start empiric antibiotics immediately; add acyclovir if encephalitis is possible.
WHO recommends lumbar puncture as soon as possible in suspected acute meningitis, preferably before antimicrobials if safe, because CSF examination identifies the pathogen and guides treatment. Blood cultures should also be obtained early, preferably before antibiotics. ([NCBI][1])
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