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Emergency and Acute Medicine – Meningitis
Basics description
Meningitis is an infection of the central nervous system characterized by inflammation of the leptomeninges and an increased white blood cell count in the cerebrospinal fluid (CSF). It commonly presents with fever, headache, neck stiffness, and altered mental status, although manifestations vary by age and immune status.
Etiology
Meningitis may be bacterial, viral, fungal, or noninfectious in origin. In neonates, common bacterial causes include group B Streptococcus, Escherichia coli, other enteric bacilli, and Listeria monocytogenes. In children and adults, Streptococcus pneumoniae and Neisseria meningitidis predominate, while elderly patients and those with alcoholism are at increased risk for pneumococcal infection, gram-negative bacilli, and Listeria. Neurosurgical patients are more likely to develop infections due to staphylococcal or gram-negative organisms. Immunocompromised patients, including those with AIDS, may develop tuberculosis, fungal, or syphilitic meningitis in addition to typical pathogens. Viral meningitis is common and often less severe, while chemical, drug-induced, or toxin-related meningitis is rare.
Clinical presentation
Typical symptoms include fever, headache, photophobia, and neck stiffness. Kernig and Brudzinski signs may be present but are neither sensitive nor specific. Patients may also develop altered mental status, seizures, focal neurologic deficits, papilledema, or a petechial or purpuric rash suggestive of meningococcal disease. Associated infections such as sinusitis, otitis media, or pneumonia may provide clues to the source.
Infants and young children often present atypically, with fever or hypothermia, lethargy, poor feeding, vomiting, respiratory distress, apnea, cyanosis, hypotonia, or a bulging fontanelle. Classic meningeal signs are frequently absent in children under one year of age. Elderly or immunocompromised patients may present primarily with confusion and fewer classic symptoms.
Essential workup
Management should begin immediately when meningitis is suspected. Blood cultures should be obtained promptly, followed by empiric antimicrobial therapy without delay, especially if the patient is unstable. Lumbar puncture is recommended for all patients with suspected meningitis unless contraindicated. Neuroimaging prior to lumbar puncture is reserved for patients at risk for herniation, including those with immunodeficiency, recent seizures, focal neurologic deficits, altered consciousness, papilledema, a history of central nervous system disease, or age over 60 years.
CSF analysis includes cell count and differential, glucose, protein, Gram stain, and culture, with additional studies added as clinically indicated. Elevated opening pressure may be present. Typical bacterial meningitis is associated with low CSF glucose, elevated protein, and a high white blood cell count with neutrophil predominance, although early disease may show fewer abnormalities.
Diagnostic tests and interpretation
Laboratory evaluation includes blood cultures, complete blood count, electrolytes, renal function tests, coagulation studies, and serum glucose for comparison with CSF glucose. Imaging such as head CT is used selectively to assess for contraindications to lumbar puncture or complications. Chest radiography may identify pneumonia or tuberculosis when suspected. Polymerase chain reaction testing and antigen detection may assist in identifying viral or bacterial pathogens when cultures are nondiagnostic.
Differential diagnosis
Conditions that may mimic meningitis include encephalitis, intracranial abscess, epidural or spinal abscess, febrile seizures, intracranial hemorrhage, stroke, systemic or central nervous system lupus, malignancy, venous sinus thrombosis, trauma, and metabolic or toxic encephalopathies.
Treatment and emergency management
Initial management focuses on airway, breathing, and circulation, seizure control, and isolation when appropriate. Empiric intravenous antibiotics should be administered as soon as possible, ideally after blood cultures but without delaying treatment for imaging or lumbar puncture. Antimicrobial regimens are selected based on patient age, immune status, and risk factors, with coverage for likely organisms. Vancomycin is added when resistant pneumococcal infection is a concern, and ampicillin is included in older adults and immunocompromised patients for Listeria coverage. Acyclovir should be started when herpes simplex encephalitis is suspected.
Adjunctive corticosteroids may reduce neurologic complications in selected patients, particularly those with pneumococcal meningitis, and should be given before or with the first dose of antibiotics when indicated.
Disposition and follow-up
Hospital admission is required for all patients with known or suspected bacterial meningitis, immunocompromised patients, and any toxic-appearing individual. Discharge from the emergency department is reserved for carefully selected patients with confirmed viral meningitis, stable clinical status, reliable follow-up, and clear discharge instructions coordinated with primary care.
Pearls and pitfalls
Meningitis rarely presents as a simple febrile seizure in children. Delayed recognition or treatment can lead to severe neurologic injury or death, making early empiric therapy essential. When clinical suspicion is high, treatment should never be postponed while awaiting diagnostic confirmation.
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