Infections of the Central Nervous system Flashcards
(50 cards)
In what ways can infection affect the CNS?
Primary CNS infection
- bacterial, viral, fungal or protozoal
- present with CNS symptoms/signs and/or systemic features of illness
Secondary CNS infection
- systemic infection with secondary CNS infection
- (e.g. endocarditis and meningitis)
Systemic infection with secondary (non-infectious CNS complications
- acute confusion with sepsis or CAP
- meningism in urosepsis
When someone presents with a CNS infection, what investigations help differentiate aetiology?
LP
Blood cultures
CT/MRI
EEG
Name some bacterial infections of the CNS.
Meningitis (-encephalitis)
- community acquired (meningo, pneumo, TB or Listeria)
- healthcare associated (post-neurosurgery or shunt related)
Brain abscess
- seeded as a result of a bloodstream infection
Neurosyphilis
Neuroborreliosis
Name some viral infections of the CNS.
HSV - herpes encephalitis is getting more common Varicella Zoster Virus Enterovirus (D-68) - causes viral meningitis/encephalitis in very young children HIV - as a presenting feature Mumps CMV West Nile JBE JCV These viruses cause encephalitis or meningitis
Name some fungal infections of the CNS.
CRYPTOCOCCUS - common in immunocomromised groups Coccidiomycosis Aspergilloma The infections cause meningo-encephalitis or mass lesions
Name some protozoal infections of the CNS.
TOXOPLASMOSIS Helminths - angiostrongylus - gnathostoma Mainly causes mass lesions - sometimes eosinophilic meningitis
What is the most important CNS infection?
Bacterial meningitis
Why is bacterial meningitis so common in Sub-saharan countries?
As this is a preventable disease, these countries probably have poor uptake of the vaccine
What are the main causes of bacterial meningitis?
Streptococcus penumoniae Neisseria meningitidus (meningococcal disease) Haemophilus influenzae Listeria Strep suis Beta-haemolytic streptoccoal meningitis
In what special cases are people immunised against bacterial meningitis other than Haemophilus, strep pneumoniae or meningococcal?
Travel to Sub-Saharan Africa and other high prevalence areas
- ACWY recommended
Asplenic and people with complement deficiency
- meningococcal boosters with Men B and ACWY
- HIB
- Penumococcal
Patients with cochlear implants
- pneumo booster every 5 years
What do you expect to see on clinical examination if the patient has meningitis?
50% of patient have neck stiffness 95% of patients have 2 of - headache - neck stiffness - fever - reduced consciousness Non-blanching rash
What are the risk factors for pneumococcal meningitis?
Middle ear disease Head injury (CSF leakage) Neurosurgery Alcohol Immunosuppression (HIV) - 100x increased risk
What are the risk factors for Listeria meningitis?
Immunocompromised
Pregnancy
- assume Listeria unless can be excluded
What are the distinguishing clinical features of a pneumococcal meningitis?
Neurology
- 65% focal signs
- 24% seizures
- 22% VIII palsy
What are the two main manifestations of meningococcal disease?
Sepsis
Meningitis
What predicts a poor outcome in pneumococcal meningitis?
Reduced GCS CN palsy CSF WCC <1000mm3 ESR elevation Age >60 with systemic complcations Age <60 with neurologic complications
What predicts a poor outcome in meningococcal meningitis?
Age >60
- more likely to present with neurologic complications
Bleeding diathesis
CNS signs
If a person has suspected meningitis, should you do a CT scan before the LP?
Not as a rule Yes if they have one of the following risk factors - Age >60 - Immunocompromised - Pre-exisiting CNS disease - Seizure - Loss of consciousness/other CNS signs - Suspected pneumococcal bacteria
If you choose to do a CT scan before the LP in suspected meningitis, what must you give the patient?
Blood cultures
Antibiotics
What would the results of the LP show in bacterial meningitis?
Neutrophils Lymphocytes Very raised protein LP glucose <50% of blood glucose Bacteria on culture and PCR - compare to blood
What would the results of the LP show in viral meningitis?
Mainly lymphocytes
Neutrophils if early
Slightly raised protein
Normal glucose
What would the results of the LP show in fungal meningitis?
Lymphocytes Raised protein LP glucose <50% of blood glucose India Ink stain shows encapsulated organisms CrAG antigen test positive
What would the results of the LP show in TB meningitis?
Lymphocytes
Raised protein
LP glucose <50% of blood glucose
Mycobacterium TB found on culture and PCR
What is the empirical antibiotic therapy for bacterial meningitis?
Age <50
- 3rd generation cephalosporin (ceftriaxone)
- maybe IVI Vancomycin if they have come from an area with high rates of resistance
Age >50 or immunocompromised
- 3rd generation cephalosporin (ceftriaxone)
- amoxicillin (increased risk of Listeria)
