CNS infections and meningitis Flashcards
- What are the routes of entry into the CNS?
Haematogenous (MOST COMMON)
Direct implantation
Local extension
PNS into CNS
- What is aseptic meningitis?
Meningitis that is caused by viruses and is not purulent
- What can neurological damage be caused by in meningitis?
Direct bacterial toxicity
Indirect inflammatory response, cytokine release and oedema
Shock, seizures and cerebral hypoperfusion
- What are the three types of meningitis?
Acute (hours to days)
Chronic (days to weeks)
Aseptic (caused by viruses so there is no pus)
- Name three organisms that cause acute meningitis.
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
- How many serotypes of N. meningitidis are there?
3 – A, B and C
NOTE: the meningitis vaccine is for meningitis C (although there is one available for meningitis B)
- List some other, rarer bacterial causes of acute meningitis.
Listeria monocytogenes
Group B Streptococcus
Escherichia coli
- How long does N. meningitidis take to cause infection?
< 10 days
- What are the four processes that occur in septicaemia?
Capillary leak – albumin and other plasma proteins lead to hypovolaemia
Coagulopathy – leads to bleeding and thrombosis, endothelial injury results in platelet release reactions, the protein C pathway and plasma anticoagulants are affected
Metabolic derangement – particularly acidosis
Myocardial failure – and multi-organ failure
- List some complications of TB meningitis.
Tuberculous granulomas
Tuberculous abscesses
Cerebritis
- What is a typical MRI feature of TB meningitis?
Leptomeningeal enhancement
- What are the most common causative organisms in aseptic meningitis?
Coxsackie group B viruses
Echoviruses
- Which age group is susceptible to aseptic meningitis?
< 1 year
NOTE: normally self-resolving after 1-2 weeks
- How is encephalitis transmitted?
Haematogenous (either person-to-person or through vectors such as mosquitoes)
- List some viruses that cause encephalitis.
Mumps
Measles
Enteroviruses
Herpes viruses
- What is becoming a leading cause of encephalitis worldwide?
West Nile virus
- Which bacterium is associated with causing encephalitis?
Listeria monocytogenes
- Name two types of amoeba that cause encephalitis.
Naegleria fowleri
Acanthamoeba species and Balamuthia mandrillaris
- What is toxoplasmosis and how is it spread?
Obligate intracellular parasite
Spread via oral, transplacental or organ transplant route
- List some organisms that can cause brain abscesses.
Staphylococci Streptococci Gram-negative organisms (mainly in neonates) TB Actinomyces and Nocardia species
- Name a common spinal infection and how does it spread?
Pyogenic vertebral osteomyelitis
direct spinal trauma
- What are some long-term consequences of pyogenic vertebral osteomyelitis?
Permanent neurologic defects
Significant spinal deformity
Death
- List some risk factors for pyogenic vertebral osteomyelitis.
Age IVDU Long-term systemic steroids Diabetes mellitus Organ transplantation Cancer Malnutrition
- List some other useful tests for suspected meningitis.
Blood culture Throat swab Blood PCR Sputum culture Urine culture
- What studies can be done with CSF?
Colour/clarity Cell counts Chemistry (protein and glucose) Stains (Gram, auramine, India Ink etc.) Cultures PCR
- Describe the typical CSF analysis results of:
a. Bacterial meningitis
b. Aseptic meningitis
c. Tuberculous meningitis
a. Bacterial meningitis Turbid High polymorphs High protein Low glucose b. Aseptic meningitis Clear High lymphocytes High protein Normal glucose c. Tuberculous meningitis Clear High lymphocytes High protein Low glucose
- Describe the Gram-stain and microscopic appearance of:
a. S. pneumoniae
b. N. meningitidis
c. L. monocytogenes
d. TB
e. Cryptococcus
a. S. pneumoniae
Gram-positive alpha-haemolytic diplococci
b. N. meningitidis
Gram-negative non-haemolytic diplococci
c. L. monocytogenes
Gram-positive rods
d. TB
Stains positively with Ziehl-Neelsen (red and blue)
e. Cryptococcus
Stains positively with India ink (appears like an orbit – yeast in the middle with a capsule around the outside)
- What is another key clinical feature of Cryptococcal meningitis?
High opening pressure
- What is the generic therapy used in meningitis?
Ceftriaxone 2 g IV BD
If > 50 years or immunocompromised = amoxicillin 2 g IV 4 hourly
NOTE: this is because ceftriaxone does NOT cover Listeria
- What is the generic therapy used in meningo-encephalitis?
Aciclovir 10 mg/kg IV TDS
Ceftriaxone 2 g IV BD
If > 50 years or immunocompromised = amoxicillin 2 g IV 4 hourly
- Name the specific therapy for meningitis caused by:
a. S. pneumoniae
b. N. meningitidis
c. H. influenzae
d. Group B Streptococcus
e. Listeria
f. Gram-negative bacilli
g. Pseudomonas
a. S. pneumoniae Pen G 18-24 mu/day b. N. meningitidis Ceftriaxone 4 g/day c. H. influenzae Cefotaxime 12 g/day d. Group B Streptococcus Pen G 18-24 mu/day e. Listeria Ampicillin 12 g/day f. Gram-negative bacilli Cefotaxime 12 g/day g. Pseudomonas Meropenem 6 g/day
