Central Nervous System Flashcards
What is the CNS protected by?
- bone and membrane layers
brain is protected by the skull, spinal cord is protected by the vertebral column
If bacteria are crossing the BBB, they are likely to cause _____
encephalitis
If bacterial are crossing the CSF, they are likely to cause ____
meningitis
What are the three ways that microbes can cross the BBB?
- growing across, infecting the cells that compromise that barrier
- being passively transported across in intracellular vacuoles
- being carried across by infected white blood cells
What is the bodies response to being invaded in the CSF?
- and increase in lymphocytes and monocytes in the CSF
- a slight increase in protein also occurs, with the CSF remaining clear (this is termed aseptic meningitis)
- the response to pyogenic bacteria shows a more rapid increase in polymorphonuclear leukocytes and proteins, so that the CSF becomes visibly turbid (this is called septic meningitis)
____ meningitis is more severe but less common
Bacterial
What are the 3 key pathogens that are known to cause bacterial meningitis ? What do these three bacteria have in common?
- neisseria meningitidis and streptococcus pneumoniae
- haemophilis influenzae
- these three bacteria all possess a capsule, allowing them to be virulent
Neisseria meningitiditis is a gram ____ diplococci
negative
In meningococcal meningitis, the infection can be asymptomatic when the bacteria possess ____ and attach to the epithelium of the _____
pili
nasopharynx
About ___% of the population is a carrier of meningococcal meningitis, with higher carrier rates during epidemics
20
People that are possessing specific complement dependent bacterial ____ to capsular antigens are protected against invasion
antibodies
Individuals that have ____ complement deficiency are more susceptible to infection
C5-C9
Young children who have ______ and adolescents who have ______ are at the greatest risk of contracting meningococcal meningitis
- lost maternal Abs
- never encountered infecting serotypes
Person to person spread takes place via ______
droplet infection due to overcrowding and confinement (in prisons, college dorms, military barracks)
When in the year is the peak time for meningitis?
- winter/early spring - carrier rates here are between 60-80%
What is the incubation time for meningitis?
- 1-3 days
What are the symptoms of sudden onset meningitis?
- headache, sore throat, drowsiness, fever, stiff neck, hemorrhagic skin rash (indicates septicemia)
What is the mortality rates in treated meningitis individuals?
- treated is 10%
What serotypes do routine childhood vaccinations vaccinate for?
Serotypes A, C, Y and W135 (routine childhood vaccination)
What tests are used to diagnose meningitis?
- essentially a gram stain of CSF, culture or white blood cell counts
There are 6 different serotypes of _____, a-f, that are distinguishable serologically by their capsular polysaccharides
Haemophilus influenzae B
Haemophilus influenzae B leads to what disease?
- haemophilus meningitis
_______ is a resident of the respiratory tract of children. Maternal antibodies protect the child until they are about 3-4 months old, but then the antibodies wane and there is a _____ before the child develops their own antibodies
- H. influenzae B
- window of susceptibility
What is the incubation period of Haemophilus influenzae?
5-6 days
Haemophilus meningitis is ___ fatal than meningococcal and pneumonococcal meningitis
less
What are the most common effects of haemophilus meningitis?
- less fatal
- but will have symptoms of hearing loss, delayed language development, mental retardation and seizures
The vaccine for haemophilus meningitis is HiB and is suitable for patients over the age of ___
2 months
Pneumonococcal meningitis is carried in the ____ of many healthy people
throats
Pneumococcal meningitis is common in which 2 demographics?
children and the elderly
- can also be in those with sickle cell disease and those with head trauma
The susceptibility of a pneumonococcal meningitis is associated with what?
- low level of capsular antibodies in the blood
- the antibody opsonizes the organism and promotes phagocytosis
- this protects the host form invasion
The mortality rate of pneumonococcal meningitis is _____ than that of H influenzae and N meningitidis
higher
What is the main bacteria that is responsible for pneumonococcal meningitis?
Strep. pneumoniae
What is the vaccine that is most used for pneumonococcal meningitis?
- heptavalent protein-conjugate (2-23 months and immunocompromised)
- 23 valent for children
What is the most common type of meningitis?
- viral meningitis
What are the general symptoms of meningitis?
- mild symptoms
- headache, fever, light sensitivity (photophobia)
- complete recovery is typical here
What is a diagnosis of viral meningitis based on?
- viral genome detection (PCR)
What kind of viruses are often the cause of viral meningitis?
- enteroviruses
What is encephalitis?
- inflammation of the brain parenchyma
What is encephalitis usually caused by?
- typically a virus
What are the most common symptoms of encephalitis?
- cerebral dysfunction
- abnormal behaviour, seizures, nausea, fever, and vomiting
What is the virus that most often causes encephalitis?
- Herpes Simplex Virus
How do neonates most often contract encephalitis?
- passage down the birth canal of a female that is shedding HSV-2
How do older children and adults most often contract encephalitis?
- HSV-1 viral replication in nerves in the skull (trigeminal ganglia) and the infection spreading back to temporal lobe of the brain
There is a __% fatality rate of encephalitis if it is not treated
70
What is the general treatment for encephalitis?
- antiviral treatment for 21 days
What are the most common symptoms of poliovirus encephalitis?
- 1-4 days of fever, sore throat, malaise, followed by signs of meningitis
- can lead to paralysis due to the effect on motor neurons
What are the two main carriers of west nile virus? What are the two incidental hosts?
- birds and culicine mosquitoes are the carriers
- humans and horses are the incidental hosts
What caused the spread of west nile virus to NA?
- migrating birds (previously only in the middle east and africa)
What are the main ways of diagnosing a west nile virus infection?
- RNA detection of IgM Ab in sera/CSF
What is the only way to control a west nile virus infection?
mosquito control
