Neurologic Infections Flashcards
What are the cranial meninges?
Three membranes surrounding the brain.
What are the three cranial meninges?
1) dura mater (outermost)
2) arachnoid mater
3) pia mater (innermost)
Where does the blood-brain-barrier NOT exist?
- vomiting centre in the medulla oblongata (to sample toxins)
- hypothalamus to detect water balance and regulate pH
What cell reinforces the blood-brain-barrier?
Astrocytes provide biochemical support to the blood vessels, ensuring they remain very impermeable.
What molecules can pass through the BBB?
lipid soluble molecules
The different type of neurologic infections are based on ____.
anatomic location and microbe, for example:
- whether it is within the brain or spinal cord
- in the meninges
- viral
- bacterial
How do pathogens gain entry to the cranium?
- fracture
- compromised BBB
- extension (ex. infection in middle ear or nostril spreads)
- along an axon
What three bacteria usually cause bacterial meningitis and what age groups are they related to?
1) Streptococcus pneumonia - adults
2) Haemophilus influenzae - kids under 5
3) Neisseria meningitidis - youth
What predisposes an individual to bacterial meningitis?
- head trauma
- neurological surgery
- congruent infection (ex. sinusitis)
- decreased immunity
What happens in bacterial meningitis? What is the pathophysiology?
- bacteria enter
- there is bacterial proliferation
- lysis of bacteria and defense cells
- this triggers inflammation
- inflammation causes purulent exudate, which moves to other tissues (brain surface, into CSF, into spinal cord)
- vasculature, ventricles and subarachnoid space also affected
What is the worry with bacterial meningitis?
Inflammation can cause swelling inside a limited space (the cranium) which can increase intracranial pressure and this is life-threatening.
What are the manifestations of bacterial meningitis?
- fever
- headache
- nausea and vomiting
- nuchal rigidity, back pain
- positive Brudzinski’s sign
- positive Kernig’s sign
How is bacterial meningitis diagnosed?
- history and presentation
- culture and sensitivity
- analyze the CSF (would find increased proteins, neutrophils, pus, decreased glucose)
How is bacterial meningitis treated?
- antibiotics
- steroids for the inflammation
What else is viral meningitis called?
aseptic meningitis
Is viral meningitis more or less severe than bacterial meningitis?
It is usually less severe because it is self-limiting. However there is still a risk of increased ICP.
What kind of exudate does viral meningitis produce?
Usually serous exudate.
If you do a CSF analysis for viral meningitis what will you find?
- increased lymphocytes
- moderate increase in proteins
- normal blood glucose
What are the signs and symptoms of viral meningitis?
- fever
- headache
- nausea and vomiting
- nuchal rigidity, back pain
- positive Brudzinski’s sign
- positive Kernig’s sign
How is viral meningitis usually treated?
- treat the symptoms, since it is self-limiting
What is encephalitis?
inflammation of the parenchyma in the brain or spinal cord
What usually causes encephalitis?
usually caused by one of the following two viruses:
1) herpes simplex type 1
2) arbovirus
What is the pathophysiology of encephalitis?
- viral particles enter
- cause localized necrosis (lysis of cells) and hemorrhage
- this causes viral particles to spread, the infection becomes generalized
- this results in edema
- the cell bodies degenerate
- unpredictable course
What are the manifestations of encephalitis?
- lethargy (general sign of infection)
- fever, headache, nuchal rigidity
- neural disturbances (seizures, coma… depends on area affected)
- severe neurologic impairment is possible… dementia or epilepsy
How long will encephalitis usually last?
2 weeks if the infection is caused by arbovirus
How is encephalitis treated?
If it is caused by arbovirus, usually just monitor and avoid complications.
If it is caused by herpes simplex it is more serious and will need aggressive treatment = IV medications, for example acyclovir (an antiviral).
What is the mortality rate for encephalitis?
30%
