Meningitis: Causes, Symptoms, Treatment, and Prevention

Meningitis is inflammation of the meninges (pia, arachnoid, dura) surrounding the brain and spinal cord, usually due to infection of the cerebrospinal fluid (CSF).

Etiology

• Bacterial (Acute, Most Severe): S. pneumoniae (pneumococcus), N. meningitidis (meningococcus), H. influenzae type b (Hib), L. monocytogenes (neonates, elderly), E. coli/GBS (neonates).
• Viral (Aseptic, Usually Self-Limited): Enteroviruses (most common), HSV-2, VZV, mumps, arboviruses, LCMV.
• Fungal: Cryptococcus neoformans (HIV/AIDS), Coccidioides, Histoplasma.
• Parasitic: Naegleria fowleri (PAM), Acanthamoeba (GAE).
• Non-infectious: Drugs, autoimmune, neoplastic, chemical.

Classic Triad (Present in ~50–70%)

• Fever, severe headache, nuchal rigidity (neck stiffness).

Additional Symptoms

• Photophobia, phonophobia, nausea/vomiting, altered mental status, seizures, focal deficits.
• Infants: irritability, poor feeding, bulging fontanelle, high-pitched cry, hypothermia.
• Petechial/purpuric rash (meningococcemia).

Diagnosis

• Lumbar Puncture (LP): Opening pressure, cell count (neutrophils = bacterial; lymphocytes = viral), glucose (low in bacterial/fungal/TB), protein (high), Gram stain, culture, PCR panel (FilmArray), cryptococcal antigen.
• Blood cultures, CBC, CRP, PCT, coagulation.
• CT head before LP if: immunocompromised, history CNS disease, seizure, papilledema, focal neuro signs, GCS <12.

Treatment

• Bacterial: Empiric IV antibiotics immediately (Ceftriaxone + Vancomycin ± Ampicillin for Listeria risk) → narrow after culture. Dexamethasone 0.15 mg/kg q6h × 4 days (with/before antibiotics) for pneumococcal meningitis.
• Viral: Supportive; acyclovir for HSV/VZV; pleconaril (investigational) for enterovirus.
• Fungal: Amphotericin B + flucytosine → fluconazole consolidation.

Prevention

• Vaccines: MenACWY, MenB, PCV13/15/20, Hib, MMR, Varicella.
• Chemoprophylaxis for close contacts of meningococcal/Hib cases (rifampin, ceftriaxone, ciprofloxacin).

Meningitis is a medical emergency. Delay in antibiotics increases mortality and neurologic sequelae (hearing loss, cognitive deficits, seizures, hydrocephalus).