What are the diagnostic criteria for meningitis (inflammation of the meninges)?

From the Guidelines

Meningitis diagnosis should be approached with a combination of clinical evaluation and laboratory tests, prioritizing immediate lumbar puncture and cerebrospinal fluid analysis to guide empiric antibiotic treatment, as recommended by the ESCMID guideline 1.

Key Considerations

• When meningitis is suspected based on symptoms like fever, headache, neck stiffness, and altered mental status, a lumbar puncture should be performed immediately to collect cerebrospinal fluid (CSF) for analysis 1.
• The CSF is examined for cell count, glucose and protein levels, and cultured to identify the causative organism, with bacterial meningitis typically showing elevated white blood cells, low glucose, and high protein in the CSF 1.
• Additional tests include Gram stain of the CSF, PCR testing for viral or bacterial DNA, and blood cultures, which can help guide targeted antibiotic therapy 1.
• Imaging studies like CT or MRI may be performed before lumbar puncture if there are concerns about increased intracranial pressure or other complications, but should not delay empiric antibiotic treatment 1.

Diagnostic Approach

• The diagnostic approach may be modified based on patient age, immune status, and local epidemiology of meningitis-causing pathogens, with the ESCMID guideline advising to start empiric treatment within one hour of arrival in all suspected meningitis cases 1.
• The choice of antibiotics needs to be differentiated according to the patient's age, risk factors, and local resistance rates of pneumococci, with dexamethasone being the only proven adjunctive treatment and should be started together with the antibiotics 1.
• Early recognition of symptoms and prompt medical attention are essential for improving outcomes in this potentially life-threatening condition, with the goal of reducing morbidity, mortality, and improving quality of life 1.

From the Research

Meningitis Diagnosis

• The diagnosis of meningitis relies on the examination of cerebrospinal fluid obtained from lumbar puncture, as clinical findings are unreliable 2, 3, 4.
• Examination maneuvers such as Kernig sign or Brudzinski sign may not be useful to differentiate bacterial from aseptic meningitis due to variable sensitivity and specificity 2.
• Delayed initiation of antibiotics can worsen mortality, and treatment should be started promptly in cases where transfer, imaging, or lumbar puncture may slow a definitive diagnosis 2, 3.

Types of Meningitis

• Aseptic meningitis is the most common form of meningitis, with an annual incidence of 7.6 per 100,000 adults, and most cases are viral and require supportive care 2.
• Bacterial meningitis is a medical emergency that requires prompt recognition and treatment, with a high mortality rate despite the introduction of vaccinations for common pathogens 2, 3.
• Viral meningitis is generally self-limited with a good prognosis 2.

Treatment and Prevention

• Empiric antibiotics should be directed toward the most likely pathogens and adjusted by patient age and risk factors 2, 3.
• Dexamethasone should be administered to children and adults with suspected bacterial meningitis before or at the time of initiation of antibiotics 2, 3.
• Vaccination against the most common pathogens that cause bacterial meningitis is recommended, and chemoprophylaxis of close contacts is helpful in preventing additional infections 2.
• Ceftriaxone is effective in the treatment of bacterial meningitis, and its rapid bactericidal activity is an advantage 5, 6.