CNS infections 061021

Question 1

what is the most common route of entry of pathogens into the CNS

Answer 1

Haematogenous

Question 2

causes of aseptic meningitis

Answer 2

enterovirus and herpes

Question 3

causes of non viral encephalitis

Answer 3

• Non-viral encephalitis:
o Bacterial – Listeria monocytogenes
o Amoeba (spread by direct extension through cribriform plates):
 Naegleria fowleri Habitat – warm water
 Acanthamoeba spp. & Balamuthia mandrillaris Brain abscess, aseptic & chronic meningitis
o Toxoplasmosis (obligate intracellular protozoal parasite – Toxoplasma gondii):
 Spread via the faeco-oral, transplacental or organ transplant route
 Causes severe infection in immunocompromised patients
 Affected organs = grey & white matter of brain, retinas, alveolar lining of lungs, heart, skeletal muscle

Question 4

myelitis causes

Answer 4

polio

Question 5

what is the neuro damage in meningitis caused by

Answer 5

• Neurological damage (10% mortality, 5% have neurological sequelae; sensorineural deafness) is caused by:
o Direct bacterial toxicity
o Indirect inflammatory process and cytokine release and oedema (n.b. tight space, oedema = bad)
o Shock, seizures and cerebral hypoperfusion
ho

Question 6

how is meningitis classified

Answer 6

o	Acute (hours to days) 
o	Chronic (days to weeks) 
o	Aseptic (caused by viruses so there is no pus)

Question 7

what serotypes of meningitis are vaccinated against

Answer 7

A, B, C, W and Y are vaccinated against

Question 8

what are the causes of acute meningitis

Answer 8

neisseria meningitidis, streptococcus pneumoniae, haemophilus influenzae

Question 9

how many serotypes of neisseria meningitidis are there

Answer 9

at least 12

Question 10

cause of meningoencephalitis in immunocompromised

Answer 10

ilisteria

Question 11

clinical features of septicaemia

Answer 11

• Capillary Leak – albumin and other plasma proteins leads to hypovolaemia
• Coagulopathy – leads to bleeding and thrombosis (endothelial injury results in platelet release reactions, the protein C pathway and plasma anticoagulants are affected)
• Metabolic Derangement – particularly acidosis
• Myocardial failure – and multi-organ failure

Question 12

chronic meningitis

Answer 12

(e.g. Tuberculous chronic meningitis) – may take weeks to develop:
o Similar presentation to acute meningitis (fever, headache, neck stiffness) but lower mortality (0.000055%)
o More common in immunosuppressed patients
o Involves the meninges and basal cisterns of the brain and spinal cord with dilatation of ventricles
o Complications:
 Tuberculous granulomas
 Tuberculous abscesses (i.e. enhancing thick-walled abscesses)
 Cerebritis

Question 13

aseptic meningitis

Answer 13

most common infection of the CNS:
o Presentation: headache, stiff neck, photophobia
o A non-specific rash may accompany these symptoms
o Organisms (80-90% of organisms) – VIRAL:
 Coxsackie group B
 Echoviruses
o Usually occurs in children <1 year
o Self-limiting disease that resolves in 1-2 weeks

Question 14

causes of focal cns infections

Answer 14

o Causative Organisms (Strep > Staph > gram -ve > other):
 Streptococci (anaerobic and aerobic)
 Staphylococci
 Gram-negative organisms (mainly in neonates)
 TB, fungi, parasites, actinomyces and Nocardia species

may be a direct extension e.g. otitis
occasionally spread through blood e.g. endocarditis

Question 15

spinal infections

Answer 15

o Pyogenic vertebral osteomyelitis is a common form of vertebral infection (e.g. staph and strep)
o Spread via… direct open spinal trauma or it can spread haematogenously

o If untreated, it can lead to:
 Permanent neurological deficits
 Significant spinal deformity
 Death

Question 16

imaging in cns infections which is better MRI or CT

Answer 16

MRI

Question 17

A 20 year old woman presents with headache and neck stiffness, what is the pathogen (gram positive cocci)

Answer 17

strep pneumoniae

Question 18

an 18 year old man presents with headache and neck stiffness, gram neg cocci

Answer 18

neisseria meningitidis

Question 19

a 65 year old man presents with headache and neck stiffness, gram positive rod

Answer 19

listeria monoctogenes

Question 20

a 45 year old man presents with headache and neck stiffness, ziehl neelsen stain positive

Answer 20

tuberculosis

Question 21

high opening pressure and indian ink stains is pathogenomic of

Answer 21

cryoptococcus neoformans

Question 22

how does encephalitis present

Answer 22

• Sx: confusion, fluctuating consciousness
• Most commonly caused by HSV1
• Rx: IV acyclovir

Question 23

risk factors for strep pneumoniae

Answer 23

Complement deficiency, hyposplenism, immunosuppressed

(alcoholic), infection (pneumonia), entry #, previous head trauma w/ CSF leak

Question 24

risk factors for neisseria meningitidis

Answer 24

Complement deficiency, hyposplenism (susceptible to encapsulated organisms), hypogammaglobulinaemia

Question 25

treatment for bacterial meninigits

Answer 25

Resuscitate! IV ceftriaxone and corticosteroids (cover Listeria with ampicillin) o If consciousness affected, consider IV acyclovir to cover encephalitis