CNS Infections Flashcards
What is special about CNS infections?
- Mode of presentation varies widely•
- Life-threatening diseases•
- Time to presentation & speed of progression varies widely•
- Prompt diagnosis with appropriate therapy is essential.
What are the 4 routes of entry into CNS?
a) haematogenous spread
b) direct implantation - via instrumentation
c) local extension - secondary to established infections
- otitis externa/media
- mastoiditis
d) PNS into CNS
- rabies
What is the most frequent route of entry in CNS infection?
Haematogenous spread
What are the CNS clinical syndromes. What region do they affect? What are the sign and symptoms? What are the causative agents?
Define meningitis
inflammatory process of meninges and CSF
Define meningoencephalitis.
inflammation of meninges and brain parenchyma
How does meningitis cause neurological damage? What is the mortality and morbidity?
Neurological damage by:
- •Direct bacterial toxicity.•
- Indirect inflammatory process and cytokine release and oedema.•
- Shock, seizures, and cerebral hypoperfusion.
Mortality ~ 10%
Morbidity ~ 5%
How do we classify meningitis?
- Acute - usually bacterial meningitis - hours
- Chronic - usually TB, spirochetes, cryptococcus - months
- Aseptic - usually acute viral
Which classification would meningococcal meningitis be?
Acute
What are the clinical features of meningitis?
What are the causes of acute meningitis?
First 3 - most common
Second 3 - less common
Listeria - important in pregnancy and immunocompromise
GBS - vaginal colonisation
E.coli - in the gut. Important in neonatal population
Describe N.meningitides.
- 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.
Meningococcus drops platelet count therefore non blanching rash.
Apart from meningitis, what can N.meningitides cause?
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).
What is the clinical presentation of septicaemia?
Describe.
CT scan - tuberculous meningitis –
enhancement in the basal cistern and
meninges, with dilatation
of the ventricles.
Describe Chronic Tuberculoud 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
Describe.
Tuberculous abscess in the left
parietal region. Note the enhancing
thick-walled abscess.
Describe aseptic meningitis.
Aseptic meningitis is the most common infection of the CNS.
Patients with aseptic meningitis have headache, stiff neck, and photophobia.
A nonspecific rash can accompany these symptoms.
Enteroviruses (e.g. Coxsackievirus group B and echoviruses) are responsible for 80-90% cases in which a causative organism of aseptic meningitis is identified.
It most frequently occurs in children younger than 1 year.
The clinical course of aseptic meningitis is self-limited and resolves in 1-2 weeks
What are the viral causes of CNS infections? What age groups do they affect? When do they occur?
What is the most common cause of encephalitis?
VIRUSES
What is the most common transmission in encephalitis?
Transmission is commonly either person to person, or through vectors:
Mosquitoes
Lice
Ticks
Various viridae from Togavirus, Flavivirus, and Bunyavirus families.
But, West Nile Virus is becoming a leading cause of encephalitis internationally…..
What are other infectious causes of encephalitis?
Bacterial encephalitis
•Listeria monocytogenes - blue cheese and mayo
Amoebic encephalitis
- •Naegleria fowleri•
- Habitat – warm water•
- Acanthamoeba species, and Balamuthiamandrillaris,
- brain abscess, aseptic or chronic meningitis.
Toxoplasmosis
- An obligate intracellular protozoal parasite, Toxoplasma gondii.•
- Via the oral, transplacental route or organ transplantation.•
- Severe infection in immunocompromised patients.
- •Affected organs include the gray and
white matter of the brain, retinas,
alveolar lining of the lungs, heart,
and skeletal muscle.
Describe the picture
Brain abscess
What is the most common route of infection in brain abscesses?
Local invasion: otitis media/mastoiditis/paranasal sinuses endocarditis/haematogenously
What causes brain abscesses?
- Streptococci* (both aerobic and anaerobic)
- Staphylococci*,
Gram-negative organisms. (particularly in neonates)
Mycobacterium tuberculosis
fungi
parasites
Actinomyces and Nocardia species
Describe spinal infections.
Pyogenic vertebral osteomyelitis common form of vertebral infection.
Direct open spinal trauma, from infections in adjacent structures, from hematogenous spread of bacteria to a vertebra.
Left untreated, it can lead to permanent neurologic deficits, significant spinal deformity, or death.
What are the RFs of spinal infections?
- Advanced age
- Intravenous drug use
- Long-term systemic steroids
- Diabetes mellitus
- Organ transplantation
- Malnutrition
- Cancer
What Ix do we use for CNS infections?
- MRI is superior to CT scanning in detecting parenchymal abnormalities such as abscesses and infarctions.•
- Central nervous system infections:
- CSF sample
- brain tissue
Describe the CSF studies?
In addition to CSF, what microbiological investigations would you do?
Blood culture,
Throat swab
Blood PCR
Fill out.
Purple = Gram +ve
Pink = Gram -ve
Cocci - spherical
Rod - Cuboidal
Gram positive cocci- pneumococcus
Gram negative cocci- meningococcus
Gram positive rod- Listeria
older immunocompromised
Ziehl-Neelsen stain- TB
Immunocompromised, high pressure chronic meningitis.
Indian ink stains- cryptococcus
What are the limitations of diagnostics
MRI oedema pattern and moderate mass effect cannot be differentiated from tumor or stroke or vasculitis in some patients.
Infections in early stages and serological tests.
Amount of CSF.
PCR techniques.
Methods to detect amoebic infections.
Availability of good laboratory technique.
How do you approach pt with possible CNS infections
Abx immediately.
What is the generic therapy
What adjunctive therapy is used in CNS infections?
- Level of care•
- Corticosteroids•
- ? Repeat lumbar puncture•
- Public health
