Infections of the Central Nervous system Flashcards
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)
How long should antibiotic treatment for pneumococcal meningitis be?
2 weeks
Increase if there are infection related complications
How long should antibiotic treatment for Listeria meningitis be?
3 weeks
Increase if there are complications
Amoxicillin, +/- gentamicin +/- Cotrimoxazole +/- Rifampicin
What is the antibiotic of choice for Listeria infections?
Amoxicillin
How long should antibiotic treatment for meningococcal meningitis be?
Usually for 5-7 days
- penicillin or ceftriaxone
What are the problems with use of Corticosteriods?
May close the BBB and prevent antibiotic absorption Neurotoxocity Bleeding Infection Hypoglycaemia in diabetics
Which patients with bacterial meningitis should get corticosteroids?
The patient has pneumococcal disease, and they are from a developed country
- dexamethasone for 4 days
- all patients are given this until it is proven not to be pneumococcal in cause
When are the benefits of corticosteriod treatment of bacterial meningitis reduced?
When presentation is delayed
The patient has untreated HIV
The patient has other life-threatening CNS infections
When should a person be given meningococcal prophylaxis?
When someone they have come into close contact with has been diagnosed with it
What is the chemoprophylaxis treatment for meningococcal prevention?
Single dose ciprofloxacin
OR
Single dose rifampicin
What is the most prominent differentiating feature of TB CNS infections?
Often causes lesions of the cranial nerves
- occulomotor
- trochlear
- abducens
- glossopharyngeal
Why can paradoxical worsening occur when treating someone for pulmonary TB?
The treatment of the pulmonary TB unmasks the TB that has disseminated into the brain.
This causes it to start to show signs and symptoms
What is the treatment for intra-cerebral TB?
Antibiotics for 1 year - Rifampicin - Isoniazid - Pyrazinamide - Ethambutamol Steriods
What is the key clinical signs to differentiate encephalitis from meningitis?
Confusion
Abnormal affect
Seizures
What do you expect to see in the CSF in viral encephalitis?
Lymphocytes
Normal glucose
What is the treatment for viral encephalitis?
IV Aciclovir for 2-3 weeks
- HSV, VSV commonly the cause
What is the treatment for viral meningitis?
Nothing, unless they are immunocompromised
What is the diagnostic test for viral encephalitis?
Viral PCR on CSF
- tested again in the second week to see if the treatment is working
What is progressive focal multifocal leucoencephalopathy?
Progressive motor dysfunction
- causes muscular weakness and death
In which patients is PMLE most common in?
Complication in renal transplants
In the immunocompromised
HIV patients
- when they start therapy
What is the cause of PMLE?
JC virus
How is PMLE treated?
No treatment
If the patient is HIV positive, it sometimes disappears with treatment of the HIV
What is intra-cerebral toxoplasmosis?
Protazoal infection of the CNS with Toxoplasma gondii
- causes multiple enhancing lesions
Who is most at risk of intra-cerebral toxoplasmosis?
Immunocompromised
HIV patients
What are the signs and symptoms of intra-cerebral toxoplasmosis?
Headaches
Seizures
Focal CNS signs
How is intra-cerebral toxoplasmosis treated?
Antibiotic
- Sulphadiazine
- Pyramethamine
Restore the immune function
What is the treatment for cryptococcal meningitis?
Amphotericin B
Flucytosine
