10A. Acute meningitis
Acute meningitis is most commonly bacterial in origin, but it can also be viral, also called aseptic meningitis. Infectious meningitides are neurological emergencies/urgencies which must be treated quickly.
Etiology
- Bacteria
- Streptococcus pneumoniae
- Neisseria meningitidis
- Streptococci
- Virus
- HSV-2
- Adenovirus
- +++
- Non-infectious
- Autoimmune disorders
- Malignant infiltration of meninges
In adults, pneumococcus and meningococcus are the most common causes.
Clinical features
The hallmark features of any meningitis are headache, fever, neck stiffness, and reduced level of consciousness, and 95% of patients have at least 2 of these at presentation. Photophobia is another possible symptom. In case of bacterial meningitis, the patient also has general signs of infection. If meningococcus is the causative agent, the patient may develop petechial rash.
In case of viral meningitis, the symptoms are usually less severe but otherwise similar as with bacterial.
Diagnosis and evaluation
Lumbar puncture and CSF analysis is essential and is performed first. The findings depend on the etiology:
| Normal | Bacterial | Viral | |
|---|---|---|---|
| Colour | Clear fluid | Cloudy, purulent fluid | Clear fluid |
| Pressure | 6 – 20 cmH2O | ↑↑ | ↑ |
| WBC | <5 cells/µL | ↑↑
Mostly granulocytes |
↑
Mostly lymphocytes |
| Protein | <0,5 g/L | ↑ | Normal |
| Glucose | 60% of blood glucose | ↓ | Normal or ↓ |
| Culture | Negative | Positive | Negative |
| CRP (in blood) | < 5 | Elevated | Normal/slightly elevated |
If there is clinical suspicion of high ICP, head CT is performed before LP, as performing LP in case of high ICP could cause tonsillar herniation. Signs which indicate a need for head imaging include seizures, papilloedema, GCS <8, focal neurological deficits, etc.
Bruzinski and Kernig sign may be positive.
Treatment
Bacterial meningitis patients should be isolated and treated with antibiotics (3rd gen cephalosporin + ampi/vanco) as soon as the lumbar puncture is taken. If CT must be taken before LP, antibiotics are given before the CT. Dexamethasone improves the outcome in pneumococcal meningitis, so it should be given as well and discontinued if another causative microbe is found.
For viral meningitis, the treatment is supportive. If HSV is likely, aciclovir can be initiated.