- Clinical science
Meningitis is a serious infection of the meninges in the brain or spinal cord that is most commonly viral or bacterial in origin, although fungal, parasitic, and noninfectious causes are also possible. Enteroviruses and herpes simplex virus are the leading causes of viral meningitis, while Neisseria meningitidis and Streptococcus pneumoniae are the pathogens most commonly responsible for bacterial meningitis. Rarer forms of bacterial meningitis include tuberculous meningitis and Lyme-associated meningitis. The classic triad of meningitis is fever, headache, and neck stiffness. In infants and young children, the presentation is often nonspecific. Patients may also present with neurological deficits, altered mental status, and seizures, indicating increased intracranial pressure (ICP). Diagnostics include physical examination followed by blood cultures and lumbar puncture. If increased ICP is suspected, a CT of the head should be performed first. Bacterial meningitis requires rapid initiation of empiric treatment. A life-threatening complication of bacterial meningitis (especially meningococcal meningitis) is Waterhouse-Friderichsen syndrome, which is characterized by disseminated intravascular coagulation and acute adrenal gland insufficiency. Viral meningitis typically resolves on its own and has a far less severe course than bacterial meningitis, which is generally fatal if left untreated.
- CSF leak after head trauma or neurosurgery
- Maternal group B streptococcal infection during birth
- Immunocompromise (e.g., due to AIDS, asplenia, heavy alcohol use disorder, chronic illness, cancer, sickle cell anemia, old age, pregnancy)
- Crowded living conditions (e.g., college dormitories, military barracks, retirement homes (listeriosis), kindergartens)
- Close contact with an infected person
Common pathogens by patient group
|Children and teenagers|
|Adults 20–60 years|
|Adults ≥ 60 years|
Less common pathogens
- Bacterial meningitis
- Viral meningitis: often associated with encephalitis (meningoencephalitis)
- Fungal meningitis
- Parasitic meningitis: helminths such as Echinococcus spp.
- Noninfectious meningitis
Pathways of infection
Most pathogens that cause meningitis colonize the nasopharynx or the upper airways before entering the CNS via:
- Hematogenous dissemination . 
- Contiguous spread of infections in nose, eyes, and ears
- Retrograde transport along or within peripheral or cranial nerves
- Direct infection (e.g., due to trauma or head surgery) 
- Bacterial meningitis: usually 3–7 days 
- Viral meningitis: usually 2–14 day, depending on the type of virus
Clinical features of bacterial and viral meningitis are similar, although viral meningitis is less acute and usually self-limiting within 7–10 days.
Often nonspecific and without the classic triad of meningitis
- Early symptoms
- Late symptoms
Children and adults
- Classic triad of meningitis: fever, headache, and neck stiffness (this triad is often not present in neonates and infants)
- Altered mental status
- Nausea, vomiting
- Possibly cranial nerve palsies
- In the case of N. meningitidis
- Common symptoms of viral meningitis
Physical examination 
Signs of meningeal irritation
Systemic signs of inflammation
- Signs of increased intracranial pressure: : e.g., (< 5% of cases) 
- Signs of underlying infections
Subarachnoid hemorrhage can manifest with the classic triad of meningitis but has a more sudden onset and patients often lose consciousness.
- Blood cultures should be performed before antibiotic therapy is started
- Blood glucose to assess CSF glucose; (see table on cerebrospinal fluid analysis in meningitis below)
- Serum studies
Lumbar puncture (LP)
- Approach: essential in all patients with suspected meningitis, unless there are signs of increased intracranial pressure (ICP), which include: 
- If LP is contraindicated: initiate empiric antibiotic: treatment immediately and conduct CT before LP to rule out ↑ ICP 
CSF studies: Gram stain and culture, PCR, and CSF analysis should all be conducted. LAT is not routinely recommended but may be considered if antibiotics were given before the LP.
- Gram stain and culture to differentiate pathogens 
- PCR: for bacterial (e.g., meningococcus) and/or viral meningitis (e.g., HSV)
Latex agglutination test (LAT; for bacterial antigen detection): enables rapid detection of meningococci, pneumococci, Haemophilus influenzae, and Escherichia coli
- No longer recommended as a routine test.
- Highly specific but sensitivity ranges from 50–90%.
- Indicated if a patient has received antibiotics prior to the LP (which could cause a culture to be falsely negative)
- Cerebrospinal fluid analysis in meningitis
|Normal||Bacterial meningitis||Viral meningitisa||Tuberculous meningitisb||Lyme meningitis ||Cryptococcal meningitis |
|Appearance|| || || || || || |
|Cell type|| |
|Cell count|| || || || || || |
|Opening pressure || || || || || || |
|Lactate|| || || || || || |
|Protein|| || || || || || |
|Glucose|| || || || || || |
a) Distinguishing tuberculous meningitis from viral meningitis based on the CSF analysis is often challenging because cell type and count in both forms of meningitis are very similar. However, lactate and glucose levels usually differ, as well as protein levels in some cases.
- CT: possible signs of ↑ ICP (e.g., effacement of the ventricles, herniation)
- MRT: gelatinous pseudocysts in cryptococcal meningitis (soap bubble appearance)
- Fundoscopic examination: papilledema if ↑ ICP
- Pathogen: Mycobacterium tuberculosis
- Incubation period: approximately 2–8 weeks
- Subacute course over several weeks or months
- Gradual manifestation with intermittent fever
- Clinical features
- Treatment: see “Treatment” in
- Pathogen: Cryptococcus neoformans (a type of encapsulated yeast)
- Exposure to pigeon droppings
- Clinical course: subacute onset with (low) fever, fatigue, and headaches
- See section on “Clinical features” above
- Meningeal symptoms are often absent
- Intrathecally amphotericin B with or without flucytosine (induction therapy lasting 10–14 days)
- Followed by fluconazole (consolidation therapy lasting 8–10 weeks and maintenance therapy lasting at least 12 months)
- 2 weeks after initiation of antifungal therapy. therapy should be delayed for at least
- See Lyme disease.
Tick-borne meningoencephalitis (primarily in Eurasia)
- Pathogen: tick-borne encephalitis virus (TBEV)
Route of infection: tick-borne
- Ixodid tick acts as a vector → transmission predominantly in June/July and September/October
- Occasional transmission via unpasteurized dairy products from infected livestock
- Incubation period: usually 7–14 days
- Clinical features:
- Treatment: symptomatic
- Full recovery is common (particularly in children and adolescents).
- In symptomatic disease, residual symptoms may occur.
Prevention: A vaccine is not available in the US.
- Active immunization with an inactivated TBEV (inactivated vaccination): Large-scale implementation of this vaccination is not generally recommended.
- The CDC's Advisory Committee on Immunization Practices (ACIP) recommends the vaccination only for individuals living, traveling, or working in high-risk areas (laboratory staff exposed to TBEV, foresters, etc.).
- Pathogen: Naegleria fowleri, an amoeba found in warm, still standing freshwater (e.g., ponds, hot springs)
- Route of infection: via contaminated water entering the nose (e.g., while swimming) → invades the CNS directly via the cribriform plate
- Clinical features: causes fulminant meningoencephalitis with rapid onset (brain-eating amoeba)
- Diagnosis: microscopy of CSF shows amoebas
- Treatment: amphotericin B
- Prognosis: nearly always fatal
Acute bacterial meningitis
- IV antibiotics for different patient groups
- < 1 month: ampicillin PLUS aminoglycoside (e.g., gentamicin) PLUS third-generation cephalosporin (e.g., cefotaxime or ceftriaxone )
- > 1 month to < 50 years: vancomycin PLUS third-generation cephalosporin (e.g., cefotaxime or ceftriaxone)
- > 50 years: vancomycin PLUS ampicillin PLUS third-generation cephalosporin (e.g., cefotaxime or ceftriaxone)
- Immunocompromised: vancomycin PLUS ampicillin PLUS cefepime OR meropenem
- Hospital-acquired: vancomycin PLUS ceftazidime OR cefepime OR meropenem
- Possibly dexamethasone: only beneficial in some cases
- In adults: when pneumococcal meningitis is strongly suspected or confirmed
- In children: for suspected or confirmed HiB meningitis
- Doxycycline (during tick-bite season in endemic areas only!)
Acute viral meningitis
- Symptomatic therapy only
- For severe cases of HSV, EBV, and VZV meningitis, consider antiviral therapy with acyclovir (IV or PO).
- Identify and treat sepsis, if present.
- Obtain blood cultures (two sets).
- Check labs: CBC, coagulation studies, CRP, procalcitonin.
- Consider indications and timing for CT head without contrast. 
- Perform lumbar puncture and order CSF analysis (if no contraindications are present).
- Begin empiric antibiotics and steroids as soon as possible (see empiric antibiotic therapy for bacterial meningitis). 
- Consider empiric viral coverage.
- 24 hours of droplet isolation for all patients suspected of having bacterial meningitis
- Consider indications for prophylactic treatment:
- Admit to medicine or neurology service.
- Consult infectious diseases.
- Consult ICU, neurology, neurosurgery departments if there are signs of altered mental status.
- Pain management
- Most common: sensorineural hearing loss (transient or permanent)
- Focal neurological deficits 
- Cognitive impairment
- Spasticity or paresis
- Cerebral edema and elevated ICP
- Communicating hydrocephalus
- Cerebrovascular disease
- Rare: brain abscess, subdural empyema, arteritis (risk of cerebral infarction and cerebral venous sinus thrombosis), ventriculitis, cerebritis
- Epidemiology: : predominantly affects small children and asplenic individuals
- Description: acute primary insufficiency of the adrenal gland most commonly caused by adrenal hemorrhage
- Pathophysiology: coagulopathy triggered by endotoxins, which often leads to hemorrhagic necrosis of the adrenal glands
- Clinical features
- Empiric antibiotic treatment (see section on “Treatment” above)
- and management of
- Prognosis: fatal without treatment and often fatal even with treatment, particularly if associated with meningococcal infection (> 40% mortality rate) 
We list the most important complications. The selection is not exhaustive.
- Fatal if left untreated
- Prognosis in treated patients depends on age, overall condition, immune status and the pathogen(s) involved.
- Viral meningitis
- Associated with neurological sequelae and a high mortality rate
- Treatment adherence is very important to avoid relapse.
- Preexposure prophylaxis: For meningococcal vaccination (a polysaccharide conjugate vaccine), see
Postexposure measures in bacterial meningitis 
- Postexposure vaccination: may be considered if the particular serogroup is known and available as a vaccine
- Postexposure chemoprophylaxis
|Postexposure prophylaxis||Drugs of choice (monotherapy)|
|Infants, children, and adolescents|