Meningococcal meningitis
Meningococcal meningitis is an acute bacterial infection of the meninges caused by Neisseria meningitidis, an encapsulated gram-negative diplococcus that spreads by respiratory droplets and classically causes a petechial rash. It is an infectious disease emergency treated with empiric ceftriaxone and vancomycin plus dexamethasone, followed by penicillin or ceftriaxone once confirmed, with chemoprophylaxis for close contacts.
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What this article covers
- Overview
Acute bacterial meningitis caused by Neisseria meningitidis, an encapsulated gram-negative diplococcus carried asymptomatically in the nasopharynx of many healthy people and spread by respiratory droplets.
- Epidemiology
N meningitidis accounts for about 14% of community-acquired bacterial meningitis in adults, behind Streptococcus pneumoniae (about 38%).
- Risk factors
Close-contact living environments: dormitories, military barracks, and other crowded settings facilitate respiratory droplet spread.
- Pathophysiology
Nasopharyngeal colonization precedes invasive disease: N meningitidis first colonizes the nasopharyngeal mucosa in asymptomatic carriers before a susceptible host develops mucosal invasion and bacteremia.
- Clinical features
Prodrome of a mild upper respiratory illness, which can precede dissemination into the bloodstream and meninges.
- Differential diagnosis
Streptococcus pneumoniae meningitis: the most common bacterial cause overall in adults; typically no petechial rash, and often associated with a contiguous focus (otitis media, sinusitis) or pneumonia.
- Diagnosis
The diagnosis is established by visualizing gram-negative diplococci on CSF Gram stain and/or growth of N meningitidis on CSF or blood culture, in a patient with a compatible clinical picture…
- Management
First, give empiric intravenous antibiotics immediately without waiting for imaging or lumbar puncture results: ceftriaxone 2 g IV every 12 hours (or cefotaxime 2 g IV every 4-6 hours as an…
- Complications
Septic shock and disseminated intravascular coagulation, reflecting severe meningococcemia.
- Prognosis
Prompt recognition and treatment substantially improve survival, while delayed antibiotic administration is strongly associated with worse outcomes.
- Prevention
Vaccination is the primary preventive measure.
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- Encephalitis
Encephalitis is inflammation of the brain parenchyma, most often viral (herpes simplex virus 1 being the classic treatable cause), presenting with fever, headache, altered mental status, and seizures; empiric IV acyclovir is started immediately whenever it is in the differential, pending confirmatory CSF PCR.
- Viral meningitis
Viral meningitis is an acute lymphocytic-predominant meningeal infection, most often caused by enteroviruses, that presents with fever, headache, and neck stiffness milder than bacterial meningitis; diagnosis rests on CSF analysis and PCR, and management is supportive care after empiric antibacterial and, when HSV cannot be excluded, IV acyclovir coverage is stopped.
- Increased intracranial pressure
Sustained intracranial pressure above 20-22 mmHg from mass effect, edema, hydrocephalus, or venous outflow obstruction, diagnosed by clinical signs plus invasive monitoring and treated stepwise with head elevation, hyperosmolar therapy (mannitol or hypertonic saline), CSF diversion, and decompressive surgery when refractory.