Meningitis pathophysiology and symptoms

Show Notes

Core EM Modular CME Course

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Patient Presentation & Workup

• Patient: 36-year-old male, currently shelter-domiciled, presenting with 3 weeks of generalized weakness, fevers, weight loss, and headaches.
• Vitals (Initial): BP 147/98, HR 150s, Temp 100.2°F, RR 18, O2 99% RA.
• Clinical Evolution: Initial assessment noted cachexia and a large ventral hernia. Following initial workup, the patient became acutely altered (A&O x0) and febrile to 102.9°F.
• Physical Exam Findings:
  • Brudzinski Sign: Positive (knees flexed upward upon passive neck flexion).
  • Kernig Sign: Discussed as highly specific (resistance/pain during knee extension with hip flexed at 90°).
  • Meningeal Triad: Fever, nuchal rigidity, and AMS (present in 40% of cases; 95% of patients have at least two of the four cardinal symptoms including headache).
• Imaging:
  • Chest X-ray: Scattered opacities (pneumonia) and a small pneumothorax.
  • CT Abdomen/Pelvis: Confirmed asplenia (secondary to 2011 GSW/exploratory laparotomy).
  • Head CT: Ventricle enlargement concerning for obstructive hydrocephalus and diffuse sulcal effacement.

CSF Analysis & Microbiology

• Bacterial Meningitis
  • Opening Pressure: Elevated (Normal is $<170$ mm H2​O).
  • Color: Cloudy or turbid.
  • Gram Stain: Positive in 60%–80% of cases before antibiotics; drops to 7%–41% after antibiotics.
  • Cell Count: Very high ($>1000$–2000/mm3 WBC); dominated by neutrophils ($>80\%$ PMN).
  • Glucose: Low ($<40$ mg/dL); CSF/blood glucose ratio is $<0.3$–$0.4$.
  • Protein: High ($>200$ mg/dL).
  • Cytology: Negative.
• Viral Meningitis
  • Opening Pressure: Normal.
  • Color: Clear or bloody.
  • Gram Stain: Negative.
  • Cell Count: Slightly elevated (<300/mm3 WBC); dominated by lymphocytes ($<20\%$ PMN).
  • Glucose: Normal.
  • Protein: Moderately elevated ($<200$ mg/dL).
  • Cytology: Negative.
• Fungal Meningitis
  • Opening Pressure: Normal to elevated.
  • Color: Clear or cloudy.
  • Gram Stain: Negative.
  • Cell Count: Elevated (<500/mm3 WBC).
  • Glucose: Normal to slightly low.
  • Protein: High ($>200$ mg/dL).
  • Cytology: Negative.
• Neoplastic (Cancer-related) Meningitis
  • Opening Pressure: Normal.
  • Color: Clear or cloudy.
  • Gram Stain: Negative.
  • Cell Count: Elevated (<300/mm3 WBC).
  • Glucose: Normal to slightly low.
  • Protein: High ($>200$ mg/dL).
  • Cytology: Positive (this is the key differentiator).

Management Protocol

• Immediate Treatment: Early administration of antibiotics/antivirals is critical to reduce mortality.
  • Antibiotics: Ceftriaxone 2g IV q12h + Vancomycin (or Rifampin in cephalosporin-resistant areas).
  • Listeria Coverage: Add Ampicillin for patients > 50 years old.
  • Antivirals: Acyclovir 10 mg/kg q8h.
  • Steroids: Dexamethasone 10 mg IV q6h for 4 days (proven to reduce mortality and improve outcomes).
• Surgical Intervention: Neurosurgery performed an emergent EVD in the ED to relieve pressure from obstructive hydrocephalus.
• Post-Exposure Prophylaxis: Indicated only for N. meningitidis (not S. pneumoniae) for contacts < 24 hours from diagnosis.
  • Regimens: Rifampin for 2 days, single-dose Ciprofloxacin, or IM Ceftriaxone (if pregnant).

Stats & Clinical Pearls: Austrian Syndrome

• The Triad: Concurrent pneumonia, endocarditis, and meningitis caused by Streptococcus pneumoniae.
• Risk Factors: Asplenia (due to the spleen’s role in filtering encapsulated bacteria), alcohol use disorder, and immunosuppression.
• Mortality Rate: Extremely high at 28%; mortality is highest when there is CNS involvement.
• Incidence: Worldwide, S. pneumoniae is the leading cause of bacterial meningitis, accounting for 3,000–6,000 cases annually.