Diagnosing Meningitis

Clinical Presentation

The American Academy of Pediatrics and other medical societies note that in adults, the most common symptoms of meningitis include fever (77-97%), headache (58-87%), neck stiffness (65-83%), and altered mental status (30-69%) 2, 3
The Infectious Diseases Society of America guidelines state that in children beyond neonatal age, common symptoms of meningitis include fever (92-93%), headache (78%), neck stiffness (40-82%), and vomiting (58-67%) 3
The Centers for Disease Control and Prevention report that a petechial or hemorrhagic rash is present in 20-52% of adults with meningitis and is highly indicative of meningococcal infection (>90% of cases) 2, 3
Clinical signs alone have poor sensitivity for diagnosing meningitis, with neck stiffness having a sensitivity of 31-51%, Kernig sign 11-53%, and Brudzinski sign 9-66%, and their absence cannot rule out meningitis 2, 3

The American College of Emergency Physicians recommends stabilizing airway, breathing, and circulation, and documenting the Glasgow Coma Scale (GCS) score 1
The Society for Healthcare Epidemiology of America guidelines state that blood cultures should be obtained within the first hour of hospital arrival, before antibiotic administration 1, 4
The Infectious Diseases Society of America notes that contraindications for lumbar puncture (LP) include focal neurological signs, papilledema, continuous or uncontrolled seizures, GCS ≤12, immunocompromised state, history of CNS disease, and new onset seizure within 1 week 1
If contraindications exist, neuroimaging should be performed before LP, as recommended by the American College of Radiology 5

The American Academy of Neurology states that CSF culture is positive in 60-90% of bacterial meningitis cases, and CSF Gram stain has excellent specificity but varying sensitivity depending on the organism 5
The Infectious Diseases Society of America guidelines report that blood cultures have varying positivity rates: 75% for pneumococcal meningitis, 50-90% for H. influenzae meningitis, and 40-60% for meningococcal meningitis 7, 6
The Society for Healthcare Epidemiology of America notes that serum inflammatory markers (CRP, procalcitonin) may help differentiate bacterial from viral meningitis, with procalcitonin threshold between 1-2 ng/ml having good discriminatory value 7

The American College of Emergency Physicians recommends starting antibiotics as soon as possible after bacterial meningitis is suspected, ideally within 1 hour of hospital arrival 4
The Infectious Diseases Society of America guidelines state that for adults, the recommended empiric regimen is cefotaxime or ceftriaxone plus vancomycin or rifampicin 4
The American Academy of Pediatrics notes that dexamethasone should be administered before or at the time of first antibiotic dose 4