Infectious Disease
CNS Infections
Infectious Disease

CNS Infections

Empiric meningitis abx by age; HSV/Lyme/cryptococcus/neurocysticercosis specifics.

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◆Bacterial meningitis — empiric therapy by age

  • •<1 month: ampicillin + cefotaxime (cover Listeria + GBS)
  • •1 mo – 50 yr: vancomycin + ceftriaxone
  • •>50 yr or immunosuppressed: vancomycin + ceftriaxone + AMPICILLIN (add Listeria)
  • •Give dexamethasone BEFORE/with first abx dose (adults)
  • •Get CT FIRST if papilledema, focal deficits, AMS, immunocompromised

◆Pathogen-specific clues

  • •S. pneumoniae: most common adult; high risk in asplenia/SCD
  • •N. meningitidis: dorms/barracks; purpuric/petechial rash → contacts get oral rifampin prophylaxis
  • •Listeria: neonates, elderly, immunosuppressed — ampicillin MANDATORY
  • •H. influenzae b: unvaccinated children; prevented by Hib vaccine
  • •M. tuberculosis: subacute fever + AMS + CN palsies; basilar meningeal enhancement on MRI

◆Viral / spirochetal

  • •HSV-1 encephalitis: fever + seizure + AMS; MRI bitemporal hyperintensities; CSF lymphocytic + RBCs. Start IV acyclovir IMMEDIATELY
  • •Lyme meningitis (Borrelia): bilateral CN VII palsy + lymphocytic aseptic meningitis; IV ceftriaxone

◆Fungal / parasitic

  • •Cryptococcal meningitis: HIV CD4 <100; ↑opening pressure + headache; CSF cryptococcal antigen; IV amphotericin B + flucytosine
  • •Neurocysticercosis (Taenia solium): immigrants from Latin America/Asia; multiple ring-enhancing/calcified lesions; albendazole + steroids

◆Other intracranial mass lesions

  • •AIDS + multiple ring-enhancing in basal ganglia → toxoplasmosis (pyrimethamine + sulfadiazine + leucovorin)
  • •AIDS + solitary periventricular ring-enhancing + EBV+ CSF → primary CNS lymphoma
  • •Cavernous sinus thrombosis: facial 'danger triangle' infection + ophthalmoplegia → MR venography + IV abx ± anticoagulation
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