CNS infections

Question 1

what is meningitis? what is it caused by?

Answer 1

inflammation of the pia and arachnoid mater. (meninges)

microorganisms (bacterial/viral/fungal)
infect the CSF

Question 2

what is encephalitis?

what is it caused by?

Answer 2

inflammation of the cerebral cortex

usually viral infections

Question 3

what is meningism?

Answer 3

term referring to the collection of symptoms experienced in meningitis

photophobia,
stiffness of neck,
severe headache

Question 4

if it is bacterial meningitis, what other symptoms normally accompany meningism?

Answer 4

fever, malaise,

rash in meningococcal sepsis !!!- characteristically hemorrhagic

Question 5

what are the 2 main causative organism of meningitis? and describe them

Answer 5

Neisseria meningitidis
gram negative diplococci

strep pneumoniae (gram pos, alpha hemolytic, optochin sensitive)

Question 6

what abx should be given in suspected bacterial meningitis (after bloods etc have been taken)

Answer 6

IV cefotaxime

Question 7

other bacteria causing meningitis in certain circumstance include

Answer 7

group B strep (beta haemolytic)- in babies, as asymptomatic carriage in 1/4 of pregnant women in the birthing canal

listeria monocytogenes- esp in immunosuppressed

H. influenza

Question 8

what adjunctive therapy can be given with IV abx to treat bacterial meningitis?

Answer 8

steroids- IV dexamethasone

reduces inflammation quickly, therefore reduced morbidity (i.e. hearing loss)

Question 9

what tests/steps would you take in suspected bacterial meningitis?

Answer 9

blood culture
abx
FBC etc other blood tests +(serology)
LP 
CT head (sometimes before LP)
throat and nose swabs

Question 10

when would you not do an LP in suspected meningitis?

Answer 10

when the clinic picture is v v suspicious of meningococcal sepsis with meninigitis (i.e. there is a rash, fever etc along with meningism symptoms)

LP is not done as danger of coagulopathy secondary to sepsis is too high and blood culture can confirm diagnosis

Question 11

A Meningitis case (neisseria meninigitidis) with meningococcal sepsis has been found. Apart from treating the px, what two things should be done?

Answer 11

inform public health England

treat close contacts with prophylactic abx

Question 12

what are the adverse effects/risks of a LP?

Answer 12

headache!!!

paraethesia
CSK leak

damage to spinal cord 
cerebral herniation (and death)(due to rapid drop in pressure)

Question 13

when obtaining a CSF sample one needs?

Answer 13

written consent from the px
manometer (to measure opening pressure)
min 5mls of CSF (more if TB suspected)

Question 14

what tests are done on the CSF sample obtained?

Answer 14

cell count
protein assay 
glucose assay 
MCS (microbio, culture, sensitivities) 
serology (for something suspected)

Question 15

what rash is very suggestive of meningococcal sepsis?

Answer 15

non blanching (when pressed with glass tumbler) 
petechial (small spots from small blood vessels hemorrhaging near the surface - purpura spots

Question 16

causes of viral meningitis?

Answer 16

enteroviruses- like echo/coxsackie
Herpes Simplex
Mumps
Measles

Question 17

Treatment of viral meningitis?

Answer 17

most are self limiting and will recover without medical treatment

but if herpes simplex virus treat with acyclovir

Question 18

how does viral meningitis appear?

Answer 18

presentation similar to bacterial
less likely to have a rash
milder symptoms

Question 19

what is encephalitis and how does it present?

Answer 19

inflammation of the cerebral cortex, caused by viral infections

presents with: 
confusion 
decreased level of consciousness (encephalopathy) 
lethargy 
fatigue

Question 20

what are the causes of encephalitis?

Answer 20

viral infections: 
herpes simplex 
varicella zoster 
parvoviruses
HIV
measels and mumps

Question 21

what is papilledma? and why might it occur in meningitis?

Answer 21

papilledma- swelling of the optic disc, as a result of raised ICP
can be caused by anything that raises ICP, but also in meningitis,

the optic nerve has a meninges sheath surrounding it, so this can cause forward pressure,
it will be bilateral

Question 22

what is botulism and what does it cause?

Answer 22

botulism is the disease caused by infection with the clostridium botulinum bacterium which produces a powerful neurotoxin called botulinum toxin, which causes flaccid paralysis

Question 23

how does botulinum toxin cause flaccid paralysis and how has it been used to treat disease?

Answer 23

botulinum toxin enters neurone axon terminal.
acts as a protease and cleaves the SNARE proteins
these proteins normally allow for the fusion of vesicles and therefore the release of ACh into the NMJ
the the toxin prevents this from occurring due to the proteins being cleaved therefore
no ACh- no signalling- no contraction of muscle (therefore flaccid paralysis)

used to treat spasms/overactive muscle diseases
also used cosmetically to reduce wrinkles by relaxing the muscle below therefore smoothing the skin