CNS Infections Flashcards
1
Q
Distribution of CNS infections
A
- hematogenous - frontal and parietal lobes; at grey-white junction
- sinus extension - frontal lobes
- otomastoiditis - temporal lobes
2
Q
Stages of pyogenic cerebritis and abscesses
A
- Early cerebritis
- Late Cerebritis
- Early Capsule
- Late Capsule
3
Q
Early Cerebritis
A
- CT - may be normal; may show an area of low density
- MR - T1 hypo, T2 hyper
- No rim enhancement
- Rx - Abx
4
Q
Late Cerebritis
A
- increased central necrosis
- fewer detectable organisms
- vascular proliferation at the periphery of the lesion
- thick, irregular contrast enhancement at the edges of the lesion
- NO discrete, hypointense capsule on T2
- Rx - Abx
5
Q
Early Capsule
A
- contrast enhanced CT and MR show a well-defined rim of enhancement
- the rim is hypointense on T2
- DWI - differentiate abscess from necrotic tumors
6
Q
Late Capsule
A
- even better defined rim of enhancement
- multiloculation is common
- capsule is iso/hyperintense on T1, hypo on T2
- the inner aspect of the enhancing capsule is often thinner than the peripheral aspect - refect decreased blood supply and fibroblast migration centrally compared to cortically!
- thin medial rim predisposes to intraventricular rupture - ependymitis/ventriculitis
- Rx - Sx
7
Q
Septic embolus
A
- infarct first
- then develop an abscess
- infarcted brain has poor blood supply - a typical capsule may not form
- complications - mycotic aneurysm of the vessel
8
Q
CNS TB infection manifestations
A
- TB meningitis (most common)
- tuberculoma
- TB abscess
9
Q
Tuberculoma
A
- hematogenous spread to the brain from lungs
- adults - most often supratentorial - frontal/pareital lobes
- pediatrics - most often posterior fossa
- most tuberculomas NOT associated with TB meningitis
10
Q
Imaging features of tuberculoma
A
- CT - multiple isodense or hyperdense nodules (due to caseous necrosis)
- target appearance - central calcfication and peripheral rim enhancement
- MR - may or may not be increased DWI, unlike pyogenic bacterial infection
- mild surrounding edema
- TB abscess - larger and multi-loculated, with more edema
11
Q
2 typs of fungal infections?
A
- endemic
- geographically restricted
- occur in both immunocompetent and immunosuppressed pts
- cosmopolitan
- occurs worldwide
- usually in immunocompromised pts
- except cryptococcus - can also occur in pts with normal immunity
12
Q
Endemic fungal infection
A
- coccidiodomycosis
- blastomycosis
- histoplasmosis
13
Q
coccidiodomycosis
A
- southwestern US
- spores inhaled - after groundbreaking for construction projects
- most pts are asymptomatic with mild resp sx
- 1% pts devellop disseminated infection and meningitis
- focal parenchymal granulomas are rare
14
Q
blastomycosis
A
- Ohio and Mississippi River valleys
- most often - meningitis
- parenchymal abscesses and granulomas often
- epidural granulomas and abscess in head and spine
15
Q
Histoplasmosis
A
- Midwest and southern US
- most often meningitis
16
Q
Fungal infection geogrphic distribution
A
- coccidiodomycosis - southwestern US
- blastomycosis - Ohio and Mississippi River valleys
- histoplasmosis - midwest and southern US
17
Q
Imaging features of fungal infections
A
- fungal granulomas - small, solid/thick rim enhancement
- fungal abscesses - seen with blastomycosis - similar to pyogenic abscesses
- fungal meningitis - leptomeningeal enhancement
- hydrocephalus - common - most often seen with coccidiodomycosis
18
Q
Cosmopolitan fungal infections
A
- cryptococcus
- aspergillosis
- mucormycosis
- candidiasis
–> most often present as meningitis
19
Q
Aspergillosis
A
- hematogenous or direct extension fr sinus
- meningitis, meningoencephalitis, abscess
- granulomas are unusual
- angioinvasion - cortical/subcortical infarcts with hemorrhage
20
Q
Mucormycosis
A
- direct extension from the sinuses, nose, or oral cavity
- diabetic and immunocompromised patients
- also angioinvasive
- the amount of peripheral edema depends on host’s ability to fight the infection
21
Q
Candidiasis
A
- meningitis, granuloma and small abscesses
- meningeal enhancement
- enhancing granulomas and microabscesses
22
Q
Cryptococcosis
A
- most frequently reported CNS fungal infection
- can occur in pts with normal immune fxn 50% of the time
- extremely common in AIDS pts
- usual manifestation - meningitis
- cryptococcomas - small multiple solid-enhancing peripheral parenchyal nodules
- gelantinous pseudocyst
23
Q
What is a characteristic cryptococcal lesion?
A
Gelatinous pseudocyst
- cystic lesion in the basal ganglia
- Virchow-Robin spaces filled with the organism
- only found in immunocompromised pts
- CT - gelantinous pseudocysts are smooth, round, low-density, no contrast enhancement
- MR - follows CSF density, no enhancement
24
Q
Parasitic infections
A
common infections encountered in the US
- cysticercosis
- echinococcosis
- toxoplasmosis
- amebiasis
25
Cysticercosis
* caused by larvae of pork tapeworm
* taenia solium
* fecal-oral route
* cysticerci (secondary larvae) cannot develop in humans and eventually die
* cysticerci that reach the CNS - parenchyma, meninges, ventricles, spine
* most common presentation - seizures
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Most common cause of seizures in Latin America?
Cysticercosis
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Types of cysticercosis
* parenchymal cysticercosis
* intraventricular cysticercosis
* meningeal infestation
* spinal cysticercosis
28
Parenchhymal cysticercosis
* most common type
* edema/nodular enhancement
* later, cysts appear - low density on CT and isointense to CSF on MR
* peripheally located, at grey-white matter junction
* scolex
* vesicular stage - no enhancement or edema
* when the cyst dies - fluid leaks into the surrounding brain - inflammation - acute encephalitis; rim enhancement
29
Intraventricular cysticercosis
* early stage - no edema, no enhancement
* late stage - when cyst dies - edema and enhancement
* obstruct foramen of Monro, 3rd ventricle, or cerebral aqueduct - hydrocephalus
* if acute hydrocephalus occurs - rapid death
* if ruptures - acute ventriculitis
30
Meningeal infestation - meningobasal cysticercosis
* often involves meninges and basal ciserns
* racemose ("clusters0 cysticercosis
* lacks a scolex but may grow - grapelike clusters
* CSF density/intensity
* hydrocephalus
31
Spinal cysticercosis
* most often intradural, can intramedullary or extramedullary
* intramedullary - ring-enhancing cord lesions
* extramedullary - racemose cysticercosis
32
Echinoccocosis
* hydatid disease
* South America, Africa, Central Europe, Middle East
* dog tapeworm
* lung and liver
* CSF density/intensity
* no edema or enhancement, unless ruptured
33
Toxoplasmosis
* congenital - women/cats - baby
* diffuse encephalitis of the fetal brain
* microcephaly
* chorioretinitis
* mental retardation
* acquired - immunocompromised pts
34
Imaging features of toxoplasmosis
* cerebral atrophy
* hydrocephalus
* calcifications in periventricular white matter, basal ganglia, and cerebral hemispheres
* congenital CMV - calcifications only periventricular in location
35
Toxoplasmosis vs CMV
* Toxoplasmosis - calcifications in the periventricular white matter, basal ganglia, and cerebral hemispheres
* CMV - calcifications only in periventricular white matter
36
Amebic meningoencephalitis
* southern US
* pts swimming in infested freshwater ponds
* nasal cavity --\> cribriform plate --\> brain
* usuall fatal
37
Imaging features of amebic meningoencephalitis
* underestimates the severity of the disease
* early - meningeal and gray matter enhancement
* late - diffuse cerebral edema
* amebic abscess - rim enhancing lesions with surrounding edema in immunocompromised patients
38
Neurosyphilis
* usually asymptomatic
* aseptic meningitis
* tabes dorsalis - posterior column degeneraqtion
* general paresis
* meningovascular disease
39
Imaging features of neurosyphilis
* usually normal
* gummas - small enhancing nodules on the surface of the brain with adjacent meningeal enhancement
40
Meningovascular syphilis
* may present as an acute stroke syndrome or a subacute illness
* thickening of the meninges
* medium and large vessel arteritis
* small infarcts in the basal ganglia, whiet matter, cerebral cortex, and cerebellum
* MR - infarcts with patchy or gyriform enhancement
* Angiography - segmental constrictions and/or occlusions of large and medium vessels
41
42
Lyme disease
* also a spirochete infection
* east coast
* cardiac, arthritis
* neurologic involvement
* peripheral and cranial neuropathy - thick, enhancign cranial nerves on MR - III to VIII; most often CN VII
* radiculopathy
* myelopathy
* encephalitis
* meningitis
* pain syndromes
* cognitive d/o
43
CNS viral infections
* CMV
* herpes simplex
* varicella zoster
* HIV
44
CMV
* primarily congenital transmission
* extent based upon the time of infection
* 1st trimester - necrosis in the germinal matrix - migrational anoamlies
* agryia
* polymicrogyria
* focal cortical dysplasia
* delayed myelination and cerebellar hypoplasia
* later - normal gyral pattern
* delayed myelination
* periventricular white matter calcifications
45
Imaging features of congenital CMV infection
* parenchymal atrophy
* ventriculomegaly
* periventricular white matter calcifications
46
Herpes simplex
* HSV encephalitis most often occurs neonates as descending the birth canal
* congenital HSV infection often leads to SA
* CT - bilateral patchy areas of low density --\> areas of necrosis --\> multicystic encephalomalacia
* in adults - reactivation of HSV-1
* hypodensity involving one or both temporal lobes
* temporal predilection due to latent virus in the gasserian ganglion
47
Gasserian ganglion
trigeminal nerve ganglion (sensory)
48
Varicella zoster
* herpes zoster ophthalmicus
* delayed contralateral hemiparesis caused by cerebral angiitis
* areas of narrowing and/or beading of the arteries
* Ramsay Hunt syndrome - facial nerve involvement
* ear pain
* facial paralysis
* vesicular eruption of the ear
49
Acute disseminated encephalomyelitis
(ADEM)
* acute demyelinating disease following viral infection or vaccination - autoimmune
* fever, headache, meningeal sx, sz
* Rx - steroids
* increased signal intensity in white matter on T2/FLAIR
* optic neuritis is common
* severe variant - acute hemorrhagic leukoencephalitis, often fatal
* acute hemorrhage leukoencephalitis in the perivascular centrum semiovale
50
Subacute sclerosing panencephalitis
* measles virus
* latent for 6 - 10 asymptomatic period
* dementia, seizures, paralysis, death
* no Rx
* imaging - periventricular white matter lesions that may enhance
51
Progressive multifocal leukoencephalopathy
PML
* JC virus
* immunosuppressed patients - AIDS
52
Encephalitis
* Rickettsia (Rocky Mountain spotted fever)
* mycoplasma pneumoniae
* Japanese encephalitis
* bilateral thalamic and basal ganglia lesions
* West Nile fever
* also increased T2 signal in the thalami and basal ganglia
* Rasmussen encephalitis
* viral childhood dz
* intractable sz
* progressive neurologic deficits
* affects one cerebral hemisphere/atrophy
53
ADEM
Appearance
54
Creutzfeldt-Jakob disease
* prion dz - transmissible proton
* rapidly progressive dementia, ataxia, myoclonus, and death
* MR - restricted difusion on DWI in cerebral cortex basal ganglia
* types
* sCJD - sporadic mutation
* vCJD - spongiform encephalopathy
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