CNS infections

Question 1

what are three examples of primary infections of the CNS

Answer 1

meningitis, encephalitis and brain abscess

Question 2

why does meningitis need to be treated right away

Answer 2

can cause life threatening sepsis and result in percent brain or nerve damage

Question 3

what are the tree classifications of meningitis

Answer 3

acute pyogenic - usually bacterial - sudden and severe

aseptic - viral, lymphocytes in the CSF

chronic - weeks/months - tubercular meningitis or cyrptococcus neofromans

Question 4

what are the ways in which meningitis can enter the CNS

Answer 4

haematogenous spread - arterial but not retrograde

direct implantation - trauma related or congenital (meingomyelocele)

local extension - infect tooth, sinuses etc

along peripheral nerves

Question 5

what are the clinical features of meningitis

Answer 5

headache, irritable, neck stiffness, photophobia

non-specific presentation in elderly, neonates and immunocomp

Question 6

how do you diagnosis acute bacterial meningitis

Answer 6

blood culture, lumbar puncture CSF for microspcy, EDTA blood for PCR

Question 7

what is dexamethasone used for and what is it effective against

Answer 7

decrease morbidity for acute bacterial meningitis for s. pneumonia but not n. meningitides

Question 8

who is affected by viral meningitis more, diagnosis and prognosis

Answer 8

children and young adults
mild symps
CSF raised lymphocyte count
full recovery expected

Question 9

what is the difference in CSF concentration for tubercular vs viral meningitis

Answer 9

viral - protein and sugar normal

t - high protein, low / absent sugar

Question 10

what is encephalitis

Answer 10

acute inflammatory process affecting the brain parenchyma

Question 11

what is the most common infection cause of encephalitis

Answer 11

viral infection

herpes virus 1 , rabies, arboviruses

Question 12

what is the most common specific viral infection of encephalitis, symptoms and management

Answer 12

herpes virus
haemorrhage encephalitis affecting temporal lobe therefore focal and epilepsy features

need aciclovir

Question 13

which viral infection has the highest fatality of any infectious disease

Answer 13

rabies

Question 14

how does rabid infect the CNS

Answer 14

bite from animal - trauma allows enter of nerve endings, advances to ganglia, spinal cord and brain - replicates in salivary glands

Question 15

what are the phases of rabies

Answer 15

prodromal phase - fever nausea headache etc
furious phase - agitation, twitching, seizures, hydrophobia
dumb phase - paralysed, disorientated
coma phase - death

Question 16

what are the features of neurosyphilis

Answer 16

acute meningitis
general paresis
tabes dorsalis
CNS invasion in 30-40% syphillis patients

Question 17

what is the definition of a brian abscess

Answer 17

focal suppurative process within the brain parenchyma (pus in the substance of the brain)

Question 18

what are the types a brain abscess can spread

Answer 18

direct spread (ear, sinus, teeth), haematogenous spread, trauma, idiopathic

Question 19

what are the microorganisms that cause brain abscess

Answer 19

usually mix
60-70% strep eg milleri
staph aureus - most common after trauma or surgery causes

Question 20

what is the presentation and management of brain abscess

Answer 20

headache, focal defect, fever, nausea, seizures, neck stiffness, papillodema

drainage if large but antibiotics if small

Question 21

what is the risk of brain abscess

Answer 21

infection can enter blood stream and csf - sepsis and meningitis risk