CNS Infections and Meningitis Flashcards
What are the 4 modes to entry for CNS infections?
- Haematogenous spread
- Direct implantation - via instrumentation
- Local extension - secondary to established infections
- PNS into CNS
What is meningitis?
Region: Meninges
Signs and symptoms: Fever, headache, stiff neck, usually some disturbance of brain function.
Causative agents: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, TB, Various viruses, Cryptococcus neoformans
What is encephalitis?
Region: Brain
Signs and symptoms: Disturbance of brain function
Causative agents: Rabies virus, arboviruses, Trypanosoma species, Prions, Amoeba.
What is myelitis?
Region: Spinal cord
Signs and symptoms: Disturbance of nerve transmission
Causative agents: Poliovirus
What is neurotoxin?
Region: CNS and PNS
Signs and symptoms: Paralysis, rigid (tetanus) or flaccid (botulism)
Causative agents: Clostridium tetani, Clostridium botulinum
What is meningoencephalitis?
Inflammation of meninges and brain parenchyma
How does meningitis cause neurological damage?
- Direct bacterial toxicity.
- Indirect inflammatory process and cytokine release and oedema.
- Shock, seizures, and cerebral hypoperfusion.
What is the prognosis of meningitis?
Mortality ~ 10%
Morbidity ~ 5%
What are the three classifications of meningitis?
- Acute
- Chronic
- Aseptic
What are signs and symptoms of meningitis?
- Vomiting
- Fever
- Headache
- Stiff neck
- Light aversion
- Drowsiness
- Joint pain
- Fitting
What are causes of acute meningitis?
Mostly bacterial causes
- Neisseria meningitidis
- Streptococcus pneumoniae
- Haemophilus influenzae
- Listeria monocytogenes
- Group B Streptococcus
- Escherichia coli
- Staphylococcus aureus
- Mycobacterium tuberculosis
- Treponema pallidum
- Cryptococcus neoformans
- Candida
- Coccidioides immitis
- Histoplasma capsulatum
- Blastomyces dermatitidis
What are features of infection with N. Meningitidis?
Infectious cause of childhood death in all countries.
Transmission is person-to-person, from asymptomatic carriers.
Pathogenic strains are found in only 1% of carriers.
Cause infections in less than 10 days.
What is a classical feature of meningococcal meningitis?
A nonblanching rash (petechial or purpuric) develops in 80% of children.
A maculopapular rash remains in 13% of children, and no rash occurs in 7%.
What are links between meningitis and septicaemia?
- 50% of cases have meningitis
- 7-10% have septicemia
- 40% have septicemia AND meningitis
Why is the clinical difference between meningitis and septicaemia important?
The clinical difference between septicemia and meningitis is important because patients who present with shock are treated differently than patients who present primarily with increased intracranial pressure (ICP).
Which 4 processes produce the clinical spectrum of septicaemia?
Capillary leak: Albumin and other plasma proteins leads to hypovolemia.
Coagulopathy: Leads to bleeding and thrombosis.
- Endothelial injury results in platelet-release reactions
- The protein C pathway.
- Plasma anticoagulants.
Metabolic derangement: Particularly acidosis
Myocardial failue: And multi-organ failure.
What is present on the CT scan of a patient with TB meningitis?
Enhancement in the basal cistern and meninges, with dilatation of the ventricles.
What is chronic tuberculosis meningitis?
Incidence: 544 per 100,000 population in Africa.
More common in patients who are immunosuppressed.
Mortality was 5.5 deaths per 100,000 persons.
Involves the meninges and basal cisterns of the brain and spinal cord.
Can result in tuberculous granulomas, tuberculous abscesses, or cerebritis.
What does a tuberculosis abscess look like on a CT head?
Enhancing thick-walled abscess.