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146 Cards in this Set

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CNS INFECTIONS - WILSON - FRIDAY JAN 26
what is the most common route for entry of infection into the nervous system?
hematogenous
what is the most common way for infectious material to be directly implanted?
secondary to trauma
what examples were given of direct extension of infectious material (2)?
1) infected tooth; 2) infected sinus
what other way can infections reach the CNS?
from the peripheral nervous system
what examples were given (2)?
1) herpes zoster (shingles); 2) rabies
ACUTE PYOGENIC (BACTERIAL) MENINGITIS
what is meningitis and in what area does it occur?
inflammation of the leptomeninges and CSF in the subarachnoid space
what visual symptoms often occur?
photophobia (abnormal visual intolerance of light)
what other symptoms often occur (4)?
1) mental changes; 2) neck stiffness; 3) fever; 4) headache
what is the most important diagnostic test for meningitis?
lumbar puncture
what happens to the pressure in the CSF?
it becomes elevated
what is the normal range?
70-180 m
what cells are found in the CSF?
PMNs (polymorphonuclear cells)
what is the normal level of mononuclear cells and PMNs?
<5 mononuclear cells; 0 PMNs - any number of granulocytes in the CSF is abnormal
what else is elevated in the CSF, and what is the normal range?
protein - normal range <40
what may be very low in the CSF in pyogenic meningitis and what is the normal range?
glucose - normal range 40-70 - glucose may be very low in pyogenic meningitis
what patients may have atypical clinical presentation or CSF findings?
immunosuppressed patients
what organisms are the most common causes of acute pyogenic meningitis in neonates (2)?
1) group B strep; 2) E. coli
what organism is the most common cause in infants?
Streptococcus pneumoniae
what is the most common cause in adolescents and young adults?
N. meningitidis
what are the most common causes in the elderly (2)?
1) Streptococcus pneumoniae; 2) L. monocytogenes
what are five main complications of acute pyogenic meningitis?
1) hydrocephalus; 2) infarcts; 3) sensory loss; 4) seizure disorder; 5) Waterhouse-Friderichsen syndrome
how is hydrocephalus caused?
leptomeningeal fibrosis obstructs CSF flow (obliterates subarachnoid space)
what might lead to cerebra/brain stem/spinal cord infarcts?
meningeal vasculitis leads to thrombosis
what types of sensory deficits may be caused (3)?
1) blindness; 2) deafness; 3) ocular palsies
what may cause these deficits?
inflammation/injury of cranial nerves
how does seizure disorder come about?
inflammatory injury of cerebral cortex results in epileptogenic foci
what organisms are particularly likely to cause Waterhouse-Friderichsen syndrome (2)?
1) meningococcus; 2) pneumococcus
what happens in WF syndrome (2) and what is the cause?
1) hemorrhagic adrenal infarction; 2) cutaneous petechiae - these result from septicemia
ASEPTIC (VIRAL) MENINGITIS
what is the difference in typical symptoms between bacterial and viral meningitis (2)?
viral meningitis is milder and self-limiting
what is the CSF pressure like?
elevated
what cells are present in CSF?
lymphocytes
what is the protein like in the CSF?
elevated
what is the glucose like in the CSF?
normal
what is the most common family of virus to cause meningitis?
enterovirus
what three specific viruses are 80% of cases due to?
1) echovirus; 2) cocksackie virus; 3) nonparalytic poliovirus
CHRONIC MENINGITIS
what does chronic meningitis frequently represent?
a meningoencephalitis
what are the most common groups of organisms to cause chronic meningitis (2)?
1) Mycobacterium (mainly tuberculosis - tuberculous meningitis) but other mycobacteria also; 2) fungi
what patients are normally affected by fungal meningitis?
immunocompromised
what are the most common organisms causing fungal meningitis (4)?
1) cryptococcus; 2) mucor; 3) aspergillus; 4) candida
which of these organisms causes meningitis frequently in AIDS patients?
cryptococcus
what other disease does a specific fungal organism have a tendency to cause meningitis on top of, and what organism is this?
mucor has a prediliction for diabetics with ketoacidosis
which fungal organisms have a major tendency to invade blood vessels (2) and produce overtly hemorrhagic lesions?
1) aspergillus; 2) mucor
how do typical symptoms of chronic meningitis compare to pyogenic meningitis?
similar, but less fulminating
what happens to CSF pressure?
elevated
what cells are found in the CSF?
mononuclear or mixed
what happens to protein in tuberculous/fungal meningitis?
elevated - may be very high
what is glucose like in CSF in chronic meningitis?
normal or moderately low
what area does chronic meningitis have a predeliction for?
basal meninges
what type of inflammatory reaction occurs?
granulomatous rather than pyogenic
what are two main problems with chronic meningitis?
1) hard to eradicate; 2) high complication rate
what complications were said to occur in chronic meningitis (4) and what does each result from?
1) hydrocephalus (from meningeal fibrosis); 2) infarcts (from vasculitis); 3) blindness/deafness/ocular palsies; 4) seizures (secondary to cortical damage)
BRAIN ABSCESS
what are the most common bacteria causing abscesses (2)?
1) streptococci; 2) staphylococci
formation of what structure is most often induced by pyogenic organisms?
fibrous capsule
what other groups of organisms cause brain abscesses in immunodeficient individuals?
1) protozoa; 2) fungi
what is the most common organism to cause abscess in immunocompromised individuals, and who does it cause it in?
toxoplasma - common cause of focal brain lesion in AIDS
what is the other most common cause of focal brain lesions in AIDS?
primary CNS lymphoma
what conditions predispose someone to brain abscesses (5)?
1) acute bacterial endocarditis; 2) cyanotic congenital heart disease; 3) chronic lung infections; 4) ear or sinus infections; 5) diseased teeth/tooth extraction
what are grave complications of brain abscess (2)?
1) herniation due to mass effect; 2) rupture into ventricles
VIRAL ENCEPHALITIS
what is encephalitis?
infection of brain parenchyma
what is viral parenchymal infection typically accompanied by?
viral meningeal inflammation (it is usually a meningoencephalitis)
what are the most characteristic histologic features of viral encephalitis (4)?
1) mononuclear cell infiltrates; 2) glial reactions; 3) neuronphagia; 4) viral inclusion bodies (intranuclear or cytoplasmic or both)
what is neuronophagia?
phagocytosis of necrotic neurons in the setting of a single-cell neuronal necrosis
what are four infective trains common to certain encephalitogenic viruses and various systemic viruses (4)?
1) tropism; 2) latency; 3) slow infection (slow-virus infection); 4) triggering factor for immune-mediated disease
what is tropism?
preferential involvement of specific types of cells or particular regions of the nervous system
what is slow infection, and what does it follow?
development of severe progressive disease after a long latency period
what is arboviral encephalitis?
arthropod born
what are the most important arboviruses in the Western Hemisphere (2 classes)?
1) Eastern/Western equine / Venezuelan / St. Louis / La Crosse; 2) West Nile
what is the most common cause of sporadic acute encephalitis in temperate areas (including US)?
type 1 HSV encephalitis
what trait does HSV-1 exemplify?
tropism
what does HSV-1 encephalitis exhibit tropism for (2)?
1) inferior temporal lobes; 2) frontal lobes
how much does labial herpes affect the level of risk?
it is not a significant risk factor
how is HSV-1 encephalitis treated?
acyclovir
who does HSV-2 mainly cause encephalitis in (2)?
1) neonates; 2) immunocompromised
what usually occurs as far as CNS infection with HSV-2 in immunocompetent individuals?
aseptic viral meningitis
who is at high risk for HSV-2 encephalitis?
neonates born vaginally to women with active primary genital herpes - indication for Caesarian section
where is encephalitis generally located in neonates?
generalized (panencephalitis) rather than tropic for inferior temporal and frontal lobes
what type of CNS infection does herpes zoster (shingles, VZV) typically cause?
a posterior ganglionitis (inflammation of a sensory ganglion)
what trait does VZV exemplify?
latency - reactivation in adulthood of chicken-pox virus
where does it remain latent, and what does it cause when released?
sensory ganglion - causes pain and vesicular skin eruption in corresponding dermatome when released
what does rabies encephalitis exemplify?
peripheral nervous system as route of entry of CNS infection
how long does it take the virus to ascend along peripheral nerves to the CNS from the bite site?
1 to 3 months
what type of disease does rabies cause (main feature)?
severe encephalitis with CNS hyperexcitability
what are two examples of CNS hyperexcitability?
1) slight touch --> pain / violent motor responses / convulsions; 2) swallowing --> pharyngospasm (hydrophobia)
what is pathognomonic for rabies?
a cytoplasmic inclusion body called a Negri body
what viruses can encephalitis arise secondary to (2)?
1) CMV; 2) PML (progressive multifocal leukoencephalopathy)
who is susceptible to CMV (2)?
1) fetuses; 2) immunocompromised
what type of lesions are seen secondary to CMV, and where are they located?
periventricular localization of necrotizing lesions (ventriculoencephalitis)
what type of virus causes PML (family) and what is it called?
JC virus - polyoma virus
who is susceptible to PML / JC virus?
immunodeficient patients
what trait does PML / JC virus exemplify?
tropism
what does it have tropism for?
oligodendrocytes
what damage does it cause in the brain?
demyelination
how susceptible is the nervous system to the effects of HIV?
it is a major target for HIV, in addition to the lymphoid system - brain, spinal cord, and peripheral nerves all susceptible
what are the predominant cells infected by HIV in the CNS (3)?
1) macrophages; 2) multinucleate giant cells; 3) microglial cells
what cells were mentioned not to appear to be infected by HIV-1?
neurons
what are the clinical symptoms of HIV infection in the CNS (5)?
1) dementia; 2) motor abnormalities; 3) ataxia; 4) incontinence; 5) seizures
what are the main pathologic changes from HIV (2)?
1) cerebral atrophy/ventriculomegaly; 2) chronic inflammation
what is seen in chronic inflammation from HIV (cells) and how are they distributed?
widely distributed microglial nodules that include multinucleate giant cells
what are two main indirect CNS consequences of HIV infection?
1) opportunistic infections; 2) primary CNS lymphoma
what opportunistic infections were mentioned to affect the CNS after AIDS (4)?
1) toxoplasmic cerebritis; 2) CMV encephalitis; 3) cryptococcal meningitis; 4) PML
what are the two most common causes of focal brain lesions in AIDS?
1) toxoplasmic cerebritis; 2) primary CNS lymphoma
what are the CNS effects of congenital AIDS (2)?
1) mental retardation; 2) motor debility
SPIROCHETAL INFECTIONS
what spirochetal infections of the CNS must we know (2)?
1) neuroborreliosis (Lyme disease); 2) neurosyphilis
is Lyme disease common, what is happening to is incidence, and why?
it is a common arthropod-borne disease, and its incidence is increasing secondary to reforestation
how many stages does Lyme disease evolve through?
three - affects multiple organ system
what is the causative organism of Lyme disease?
Borrelia burgdorferi
in what % of untreated individuals does neurosyphilis develop?
10%
what stage of syphilis is neurosyphilis?
tertiary stage
what is the causative organism of neurosyphilis?
Treponema pallidum
TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES
what are these the only known infectious agents that are devoid of?
nucleic acid
what types of etiologies can prion diseases be due to (3) and what is the mechanism of each?
1) sporadic (spontaneous alteration of conformation of PrPc); 2) genetic (mutation of gene encoding PrPc); 3) infectious (inoculation of PrPSc into host)
what does disease result from?
accumulation of PrPSc
what is the fundamental event underlying prion diseases (specific change)?
structural transition from alpha-helices to beta sheet in PrP (transition from PrPc to PrPSc)
what are prion diseases a localized form of?
amyloidosis
what do particular diseases appear to be associated with?
particular isoforms of PrPSc (which can have a variety of conformations)
what is the spectrum of symptoms like (list)?
dementia, ataxia, insomnia, paraplegia, parasthesias, deviant behavior
what pathologic change was mentioned, and how does it vary?
vacuolation - spongiform degeneration of the tissue - varies from sparse to widespread
what accounts for 85% of prion disease in humans?
sporadic Creutzfeld-Jakob disease (CJD)
what % of prion diseases are infectious?
<1%
how can patients acquire CJD from infectious method (2)?
1) contaminated grafts, hormone preparations, corneal transplants, EEG electrodes, etc. 2) contaminated beef
what are inherited forms of CJD (3)?
1) familial CJD; 2) Gerstmann-Straussler-Scheinker disease; 3) fatal familial insomnia
what are the typical manifestations of CJD (2)?
1) myoclonus; 2) dementia
what is the course of CJD?
progressive and rapidly fatal (1 year)