meningitis/encephalitis

• Bacterial meningitis


  Risk = colonization of nasopharynx with spread to blood then central nervous system (CNS); CNS invasion from bacteremia from body source (pneumonia, endocarditis abscess, pyelonephritis); direct entry from contagious infection
• Patients at risk for bacterial meningitis

  • Poor vaccination history
  • Spleen issues
  • Immunocompromised
  • Surgical history or trauma
• Pathogens causing bacterial meningitis

  • Streptococcus pneumoniae in US
  • Group B Streptococcus in infants
  • Neisseria meningitidis in college students
  • Listeria in very old/young population
• Epidemiology of bacterial meningitis

  1.2 million cases worldwide, 25% mortality, typically in winter months
• History of bacterial meningitis

  • Rapid progression < 24 hours
  • Fever
  • Neck pain
  • Headache
  • Altered mental status
• Physical exam findings in bacterial meningitis

  • Fever
  • Meningismus (Kernig's/Brudzinski's signs)
  • Nuchal rigidity
  • Accentuation of headache with joint movement
  • Seizures
  • Focal neurological deficits (cranial nerve deficits)
  • Papilledema
  • Skin rashes
• Laboratory tests for bacterial meningitis

  • CBC with differential
  • Comprehensive metabolic panel (hyponatremia, elevated anion gap)
  • CRP (elevated)
  • Procalcitonin (< 0.25-0.5 ng/mL)
  • PT/PTT, lactic acid (elevated/normal)
  • Blood cultures x2
  • Urine analysis and culture
  • CSF analysis
  • CXR (pneumonia)
• CSF/Gram stain findings in bacterial meningitis

  • Gram stain for early pathogen recognition
  • CSF: low WBC/RBC, protein 15-45, glucose 50-80, lactate < 3.5
• Aseptic meningitis


  Risk = viral, fungal, parasitic, spirochete, neoplasm, drugs
• Epidemiology of aseptic meningitis

  1. 10 per 100,000 in US
• History of aseptic meningitis

  • Self-limiting, improves without treatment
• CSF findings in aseptic meningitis

  Leukocytosis with mostly lymphocytes, normal glucose, elevated protein
• Viral meningitis


  Risk = enterovirus, HSV, HIV, West Nile virus, VZV, mumps, CMV, COVID-19
• Classic triad of meningitis

  Fever, nuchal rigidity, altered mental status
• Encephalitis


  • Etiology = viral, HSV-1/2/varicella zoster, Japanese encephalitis, autoimmune, tick-borne, CMV, EBV, adenovirus, influenza A, enteroviruses, MMR, rabies, arbovirus, bunyaviruses, reoviruses, arenaviruses
  • Pathology = acute inflammation of brain parenchyma
• History and exam findings in encephalitis

  • Abnormal brain function (focal neurologic signs) - altered mentation/behavior, motor/sensory deficits, speech/movement disorders, personality changes, seizure
  • Fever, headache, behavioral changes, altered level of consciousness, focal neurologic deficits, seizures
• Laboratory tests for encephalitis

  • AMS labs (blood, urine, CT head, X-ray, LP, viral studies)
  • CSF analysis
  • MRI without contrast with FLAIR
  • Brain biopsy