Infections of the CNS ✅ Flashcards
What is the peak age of bacterial meningitis?
2 years
What has produced a decrease in cases of bacterial meningitis?
Vaccines
What bacteria causing meningitis can be vaccinated against?
- N. meningitidis
- S. pneumoniae
- H. influenzae
What % of cases of meningitis are aseptic in countries with routine use of vaccines?
90%
What is the most common pathogen causing meningitis?
Enteroviruses
What are the most important organisms causing meningitis in neonates?
- GBS
- E. coli
How does the incidence of encephalitis compare to meningitis?
Encephalitis is less common
What pathogens cause encephalitis?
Viruses, most commonly HSV
Where does infection usually start in bacterial meningitis?
The nasopharynx
How can infection in the nasopharynx lead to bacterial meningitis?
Nasopharyngeal infection is followed by bacteraemia and subsequent penetration of the blood brain barrier
What happens once bacteria have entered the CSF?
They continue to proliferate
What does the proliferation of bacteria in the CSF stimulate?
A pro-inflammatory cascade
Other than the CSF, where can the proliferation of bacteria cause a pro-inflammatory cascade in meningitis?
In the blood
What is produced when a pro-inflammatory cascade is stimulated in the blood due to the proliferation of bacteria?
Septicaemia
What does the pro-inflammatory cascade stimulated by proliferation of bacteria lead to in the CSF?
Upregulation of specific adhesion molecules and recruitment of leukocytes into the CSF
How does CNS damage occur in bacterial meningitis?
- Directly due to meningeal irritation
- Indirectly due to circulatory collapse
What is the result of meningeal damage in bacterial meningitis?
High rates of neurological sequelae
How can death occur in bacterial meningitis?
Cerebral oedema
How can cerebral oedema lead to death in bacterial meningitis?
- Raised intracranial pressure
- Cerebral or cerebellar herniation
How does the inflammatory response to viral meningitis compare to bacterial?
It is much less severe in viral meningitis
How can organisms reach the brain in encephalitis?
- Via the blood
- Via neuronal tract
What is produced when organisms reach the brain via the blood in encephalitis?
Diffuse infection
What is produced when organisms reach the brain via neuronal tracts in encephalitis?
Localised disease
What produces immune mediated encephalitis?
Inflammatory lesions
What produces inflammatory lesions in immune mediated encephalitis?
- Host response to infection
- Presence of auto-antibodies
What are the early complications of bacterial meningitis?
- Seizures
- SIADH
- Subdural effusions
- Focal neurological abnormalities
- Hydrocephalus
- Abscesses
- Venous sinus thrombosis
What % of children with bacterial meningitis can long-term sequelae?
20-30%
What are the potential long-term sequelae of bacterial meningitis?
- Sensorineural hearing loss
- Epilepsy
- Motor and cognitive impairment
- Blindness
- Learning/behavioural problems
What is the fatality rate of meningitis in developed countries?
5-10%
What is the prognosis of viral meningitis?
Full recovery is usual, although neuropsychological sequelae can occur
What is the fatality rate of viral encephalitis?
3-4%
What is the fatality rate of viral encephalitis neonates?
40-50%
