Last updated:
January 17, 2026
Table Of Contents
Meningitis
Meningitis is an infection and inflammation of the meningeal linings. It is important to start IV empiric therapy (ideally, treatment should be started as soon as CSF analysis results are back). The #1 cause of meningitis is Streptococcus pneumoniae. Viral meningitis is usually self-limited.
The majority of patients present within a few days of symptom onset for acute bacterial meningitis since the infection is more aggressive
Causes of meningitis according to the population
| Population | Organism |
|---|---|
| Young individuals with a petechial rash | Neisseria meningitidis |
| Neonates | Streptococcus agalactiae (GBS; due to vertical transmission) |
| Children < 2 years and adults > 60 years old | Listeria monocytogenes |
| Post-operative | Staphylococcus aureus (due to contamination) |
| HIV positive (AIDS , 100 CD4 cells/ul) | Cryptococcus spp. |
| Pulmonary Tuberculosis | Mycobacterium tuberculosis |
| Rare causes | Treponema pallidum (neurosyphillis), Rickettsia (RMSF), Borrelia (Lyme Disease), *Naegleria fowleri (*primary anaerobic meningoencephalitis) |
- Risk factors for community acquired meningitis
- Homelessness
- Living in group settings e.g. dorms, barracks
- Asplenia
- Diabetes
- Other risk factors for meningitis
- Sinusitis
- Mastoiditis
- Otitis
- Endocarditis
- Penetrating head trauma
- Basilar skull fracture
- Recent neurosurgical procedure
- Alcoholism
- HIV
- Signs and symptoms
- Fever
- Headache
- “Stiff neck”/ Nuchal rigidity
- Vomiting (non-specific)
- Photophobia
- Kernig sign (pain on hip flex/knee extension)
- Brudzinski sign (involuntary leg lifting on neck flexion)
- Rash (Particularly in young people. Does not fade when a glass is pressed against it. Do a thorough dermatological exam → if present start 3rd gen cephalosporin)
- Investigations
- Head CT: best first step before lumbar puncture; especially in patients with elevated intracranial pressure or risk of intracranial pressure (immunocompromised)
- LP with CSF analysis: Technically the best first step in patients without signs of elevated intracranial pressure
- CSF culture: most accurate test, does not play a role in treatment
- Treatment
- IV empiric therapy
- IV Vancomycin AND 3rd gen cephalosporin (Cefotaxime, Ceftriaxone): to cover Strep and Neisseria. Vancomycin has better meningeal penetration
- Meropenem and Vancomycin for resistant hospital acquired infection
- Vancomycin, moxifloxacin or trimethroprim-sulfamethoxaxole for B-lactam allergy
- Other options
- IV Ampicillin: if patient is <2y, >60y, or immunocompromised to cover for Listeria
- Amphotericin B: Cryptococcal meningitis
- Quadruple therapy (INH, Rifampin, Pyrimethamine, Ethambutol): TB meningitis
- High dose Penicillin – Syphilitic meningitis
- Seizure precaution (if the patient is severely symptomatic)
- Follow up for possible neurological sequelae (Seizure disorders, SNHL) particularly in children
- No role for steroids in acute bacterial meningitis
- IV empiric therapy
- Complications
- Permanent neurological deficit (commonly sensorineural hearing loss)
- Seizures
- Cognitive impairment
- Secondary intracranial infection e.g. empyema
- Waterhouse-Freidrischen syndrome
CSF analysis: 3 major parameters are read in a CSF analysis – Protein, glucose, and cell count
| Parameters | Normal | Bacterial | Viral | Cryptococcal | TB | Aseptic |
|---|---|---|---|---|---|---|
| WBC (cells/uL) | 0-5; lymphocytes | 100-5000; >80% PMNs | 10-300; lymphocytes | 100-200; lymphocytes | 100-500; Lymphocytes | 10-300; lymphocytes |
| Glucose (mg/dL) | 50-75 | Reduced | Normal | Reduced | Reduced | Normal |
| Protein (mg/dL) | 15-40 | Elevated | Normal, may be slightly elevated | Elevated | Elevated | Normal, may be slightly elevated |
| Microbiology | Negative findings on workup | Specific pathogen | PCR analysis | India ink, CRAG, culture | AFB stain, PCR, Culture | Negative findings on workup |
| Parameter | Interpretation |
|---|---|
| Elevated protein | All causes of meningitis |
| Normal glucose | Non-bacterial meningitis. Glucose could also be low in cryptococcal meningitis |
| Elevated Polymorphonuclear cells | Bacterial meningitis |
| Elevated lymphocytes | Viral meningitis, Cryptococcal meningitis, TB meningitis, Aseptic meningitis |
Waterhouse-Friedrichsen syndrome
Waterhouse-Friedrischen syndrome is a very feared complication of meningococcemia that results in bilateral haemorrhage into the adrenal glands, causing severe acute adrenal insufficiency
- Signs and symptoms
- Hypotension
- Hyponatremia
- Hyperkalemia
- Thrombocytopenia
- Other symptoms of sepsis
- Treatment
- 3rd gen cephalosporin (Cefotaxime, Ceftriaxone)