CNS infections Flashcards
what are the main causative organisms in viral encephalitis ?
HSV
chicken pox measles
Enterovirus
bacterial meningitis can be classified into?
acute pyogenic meningitis
chronic meningitis
localized bacterial infections can be classified into
abscess
empyema
what are the main causative organisms of acute pyogenic meningitis ?
E.coli or group B streptococci ( in infants)
Neisseria meningitides ( young adults)
streptococcus pneumonia ( older patients)
what is the main causative organism in chronic meningitis ?
mycobacterium tuberculosis
what are the CNS infections caused by viruses ?
acute aseptic meningitis
encephalitis
brain stem and spinal cord syndrome
what is meningitis ?
an acute inflammatory process involving the leptomeninges ( arachnoid and pia mater)
what is the degree of exudate extension in meningitis ?
it may extend into the perivascular virchow robin spaces
however direct extension into the brain is rare
what are the types of infectious meningitis ?
acute pyogenic
aseptic
chronic
how can you differentiate between the various subtypes of infectious meningitis ?
CSF examination
what are the bacteria most commonly causing bacterial meningitis?
Children under 10 years:
streptococcus pneumoniae
neisseria meningitides
Newborn period:
Group B streptococci
E.coli and listeria
Adults:
streptococcus pneumonia
what is the gross picture in acute pyogenic meningitis ?
evident purulent exudate within leptomeninges on the surface of the brain , sulci are obscured by the exudate
what are the typical CSF findings in in acute bacterial meningitis?
low glucose
high protein
high cell count with many PMN
Lactate dehydrogenase is also increased with bacterial meningitis
how do we obtain a CSF sample ?
through a lumbar puncture
what do we have to check before proceeding with a lumbar puncture ?
we have to check for papiloedema ( increased intraocular pressure) this means that intracranial pressure is too high to safely perform a lumbar puncture
what are the typical CSF findings in viral infections?
low white blood cell count
predominance of lymphocytes
normal to elevated protein levels
CSF to glucose ratio is usually normal
what are the CSF findings in fungal infections ?
predominance of lymphocytes
elevated protein levels
low glucose levels
what are the CSF findings in tubercular infections?
predominance in lymphocytes
elevated protein levels
low glucose levels
what are the classifications of CNS tuberculosis ?
Intracranial
spinal
chronic meningitis?
TB
what is tuberculous encephalitis ?
a syndrome exclusively present in infants and children
what is the presentation of tuberculous encephalitis ?
comes in the form of stupor, convulsions , coma but without meningeal irritation or focal neurological deficit
gross picture of a tuberculoma?
well circumscribes greyish white lesion with some fibrous encapsulation
what would you find microscopically in a tuberculoma ?
giant cells
caseous necrosis
epitheliod cells
what stain is used to identify TB
Zeihl neilson acid fast stain
what kind of necrosis occurs with brain abscess ?
liquefactive necrosis
what is a tuberculous brain abscess ?
an encapsulated collection of pus containing viable tubercular bacilli without a definite tubercular granuloma
what would the microbiology of the tuberculous brain abscess show ?
TB bacilli
what is the gross presentation of cryptococcal meningitis ?
Cerebral cortex shows multiple small cyst-like structures throughout the gray and white matter (soap bubble lesions)
what do the cyst like structures in cryptococcal meningitis correspond to ?
corresponding to dilated perivascular (Virchow-Robin) spaces
what do the ‘soap bubble lesions’ contain ?
contain mucoid material characteristic of Cryptococcal meningitis
inflammatory response in cryptococcal meningitis ?
barley
what are the characteristic location involvement in HSV encephalitis ?
inferior and medial temporal lobes
what damage does HSV produce in the cerebral cortex?
hemorrhagic meningoencephalitis , The virus directly infects cells in the cerebral cortex, causing necrosis and a glial reaction
what are the layers surrounding BV in HSV encephalitis ?
BV surrounded by lymphocytic infiltration which surrounded by haemorrhage causing necrosis
how do CNS infections reach intracranial structures?
through hematogenous spread
direct extension from nearby structures
direct source ; trauma injury
if we want to give empirical ab what to give ?
3rd generation cephalosporins ( cetriaxone)
what ab to give with a confirmed case of meningococci meningitis ?
Penicillin G
what are the antimicrobial prophylaxis required for close contact patients
single dose ciprofloxacin
or
rifampicin
what are the preventative measures of bacterial meningitis ?
vaccination against strep pneumonia and
N.meningitidis C and
H.influenza
how do we treat the complications of bacterial meningitis ?
for the dehydration ( IV fluids)
give dexamethasone to decrease oedema
give anticonvulsants
what antibiotic to use with anaerobic bacteria ?
metradinazole
what is the surgical treatment for brain abscess ?
stereotactic aspiration of the brain abscess , excision
what to give for raised intracranial pressure ?
mannitol IV
how to treat and manage a case of viral encephalitis?
control fever
give antivirals - acyclovir for 2 weeks
proper anti epileptic drugs
treatment for fungal meningitis ?
symptomatic treatment
what would confirm a diagnosis of Rabies ?
saliva testing , ab in CSF
what is the treatment for rabies ?
human rabies vaccine
locked jaw and gave birth recently ?
ask about tetanus shot (clostridium tetani)
