Neuroinfectious disease and neuroimmunology
Neuroinfectious disease and neuroimmunology
The exam tests CSF interpretation, empiric treatment, and overlap between infection and autoimmunity. Bacterial meningitis requires urgent antibiotics and dexamethasone; do not delay antibiotics for lumbar puncture if signs of raised ICP are present. Viral encephalitis, especially HSV, causes fever, headache, seizures, and temporal lobe changes; start acyclovir early because PCR can be negative initially. TB meningitis shows lymphocytic CSF, low glucose, and high protein; treat empirically when suspicion is high. HIV and neurosyphilis remain important causes of meningitis, stroke, and cognitive change. Autoimmune encephalitis can follow HSV and may require immunotherapy.
Worked example
A 40-year-old has fever, confusion, and a temporal lobe seizure. Reasoning: HSV encephalitis until proven otherwise. Start IV acyclovir and antibiotics after blood cultures, obtain CSF when safe, and add immunotherapy only after infection is addressed.
Traps
Do not delay antibiotics for CT or LP in suspected bacterial meningitis; do not rely on an early negative HSV PCR; do not miss neurosyphilis; do not attribute all encephalitis to autoimmunity without excluding infection; remember that TB meningitis needs prolonged treatment.