CNS infections and meningitis Flashcards
What are the four routes of entry?
Haematogenous spread
Direct implantation
Local extension
PNS into CNS
What are the signs and symptoms of meningitis?
Fever
Headache
Stiff neck
Disturbance of brain function
What are the causative organisms in meningitis?
N. meningitidis S. pneumoniae H. influenzae TB Viruses Fungus- cryptococcus neoformans
What does encephalitis cause?
Disturbance of brain function
What organisms are implicated in encephalitis?
Rabies Arboviruses Trypanosoma species Prions Amoeba
What is myelitis?
Disturbance of nerve transmission
What causes myelitis?
Poliovirus (poliomyelitis)
What do neurotoxins cause?
Paralysis both rigid (tetanus) and flaccid (botulism)
What organism causes neurotoxin related paralysis?
Clostridium tetani
Clostridium botulinum
What is affected in meningitis?
inflammatory process of meninges and CSF
What is affected in meningoencephalitis?
inflammation of meninges and
brain parenchyma
What causes neurological damage in meningitis?
Direct bacterial toxicity.
Indirect inflammatory process and cytokine release and oedema.
Shock, seizures, and cerebral hypoperfusion.
What is the mortality of meningitis?
Mortality rate around 10%
In the UK, (Morbidity) ~ 5% of meningitis survivors have neurological sequelae, mainly sensorineural deafness.
How do you class meningitis?
Acute - bacterial
Chronic - TB, syphilis, cryptococcal (Immunodef)
Aseptic - Viral
What most commonly causes acute meningitis?
- Neisseria meningitidis
- Streptococcus pneumoniae
- Haemophilus influenzae
Less common:
Listeria monocytogenes
Group B Streptococcus
Escherichia coli
What is the aetiology/ pathological sequelae of meningitis through 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.
Through nasopharyngeal mucosa in a susceptible individual.
Cause infections in less than 10 days.
What type of rash is associated with meningococcal septicaemia?
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%.
How many people get septicaemia with N meningitidis?
50% of cases have meningitis
7-10% have septicemia
40% have septicemia AND meningitis
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 4 processes lead to the clinical spectrum associated with 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 failure -> multi-organ failure.
What is the: Epidemiology Aetiology Histopathology of TB 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 is the: Epidemiology Aetiology Histopathology of 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.
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 most important viral causes of CNS infection?
Enteroviruses (all ages- summer to autumn)
HSV 1/2 (adults summer - autumn)
Coxsackie Virus B
Which viruses cause CNS infections in children/ YA?
Mumps Measles Varicella-zoster Epstein-Barr virus/ cytomegaloviruses Other (myxoviruses, paramyxoviruses, adenoviruses)
What is the typical mode of transmission in encephalitis?
Person to person or vector (lice, mosquito, ticks)
What are the viral causes of encephalitis?
Arboviruses Western equine encephalitis St. Louis encephalitis California encephalitis Eastern equine encephalitis Rabies
What is most likely to cause bacterial encephalitis?
Listeria monocytogenes
What organisms cause amoebic encephalitis?
Naegleria fowleri
Habitat – warm water
Acanthamoeba species, and Balamuthia mandrillaris,
brain abscess, aseptic or chronic meningitis.
What is 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
What may cause a brain abscess?
otitis media/mastoiditis/paranasal sinuses
endocarditis/haematogenously
Which organisms are associated with brain abscesses?
Streptococci (both aerobic and anaerobic)
Staphylococci,
Gram-negative organisms. (particularly in neonates)
Mycobacterium tuberculosis
fungi
parasites
Actinomyces and Nocardia species
Why are spinal infections bad?
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 for spinal infections?
Advanced age Intravenous drug use Long-term systemic steroids Diabetes mellitus Organ transplantation Malnutrition Cancer
Which diagnostic modality would be useful in diagnosis?
MRI > CT if soft tissue issue (like abscesses and infarctions)
CNS infection = CSF sampling and biopsy
What can you order with CSF?
Color/Clarity Cell counts Chemistry (Protein/ Glucose) Stains (Gram/ Auramine/ India Ink) Cultures \+/- Antigen screens PCR
Describe the 1. appearance 2. cells present 3. gram stain/ Ag test 4. protein 5. glucose in a normal CSF sample
- Clear
- 0-5 leukocytes
- negative staining/Ag
- 0.15-0.4 g/L
- 2.2 -3.3 mmol/l (60% blood glucose level)
Describe the 1. appearance 2. cells present 3. gram stain/ Ag test 4. protein 5. glucose in purulent meningitis (e.g. bacterial)
- Turbid
- 100 - 200 polymorphs
- positive
- 0.5-3.0 g/l
- 0-2.2
Describe the 1. appearance 2. cells present 3. gram stain/ Ag test 4. protein 5. glucose in Aseptic meningitis
- clear or slightly turbid
- 15 - 500 lymphocytes
- Negative
- 0.5-1.0 g/l
- normal
Describe the 1. appearance 2. cells present 3. gram stain/ Ag test 4. protein 5. glucose in TB meningitis
- clear or slightly turbid
- 30 - 500 lymphocytes / polymorphs
- Negative - scantly AF bacilli
- 1.0-6.0 g/l
- 0-2.2
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.
What drugs do you give meningitis pts?
Ceftriaxone 2g iv bd
If >50yrs or immunocompromised add:
Amoxicillin 2g iv 4hourly
What drugs do you give meningoencephalitis pts (generically)?
Aciclovir 10mg/kg iv tds
Ceftriaxone 2g iv bd
If >50yrs or immunocompromised add:
Amoxicillin 2g iv 4hourly
What is the recommended therapy for S pneumoniae or N meningitidis meningitis?
Pen G 18-24 mu/d or Ampicillin 12 g/d or Ceftriaxone 4 g/d or Chloro 75-100 mg/kg/d
What is the treatment for H influenzae and G-ve bacilli?
Cefotaxime 12 g/d or Ceftriaxone 4g/d
What is the treatment for listeria meningitis?
Ampicillin 12 g/d or Pen G 18-24 mu/d
[plus aminoglycoside]
What is the treatment for Gp B strep meningitis?
Pen G 18-24 mu/d or Ampicillin 12 g/d
[plus aminoglycoside]
What is the treatment for pseudomonas meningitis?
Meropenem 6g/d or Ceftazidime 6g/d
What adjunct therapy is available?
Level of care
Corticosteroids
? Repeat lumbar puncture
Public health
What class of meningitis is meningococcal meningitis?
Acute
Which pathogen is revealed by india ink?
Cryptococcus (neoformans)
