CNS Infection

Question 1

intracranial bacterial infections

Answer 1

pyogenic abscess, tuberculoma, lyme disease

Question 2

pyogenic abscess cause, appearance

Answer 2

cause: hematogenous dissemination, direct spread from paranasal sinuses/mastoids, complication of bacterial meningitis
appearance: T2 hypointense rim, restricted diffusion

Question 3

stages of pyogenic infection

Answer 3

early cerebritis, late cerebritis, early abscess, late abscess; 2 weeks to develop

nonspecific T2 prolongation with eventual rim enhancing mass with thin/smooth rim

Question 4

tuberculoma

Answer 4

localized TB granuloma; central hypointensity

similar to pyogenic abscess

Question 5

lyme disease

Answer 5

spirochete Borrelia burgdorferi; T2 prolongation within the frontal subcortical white matter

enhancement of CN or meninges too

Question 6

cryptococcus

Answer 6

cryptococcus neoformans; fungal infection
most common CNS fungal infections in AIDS (CD4 < 100)

chronic basilar meningitis; hydrocephalus
spreads via basal ganglia perivascular spaces leaving behind gelatinous peudocysts; produce cryptococcomas within the ventricles via choroid plexus

treat with fluconazole/amp B

Question 7

most common CNS infectsions in AIDS

Answer 7

HIV encephalopathy, toxoplasmosis, cryptococcus

Question 8

parasitic CNS infections

Answer 8

neurocysticercosis, toxoplasmosis

Question 9

neurocysticercosis

Answer 9

Taenia solium tapeworm; common in immunocompetent patients; presents with seizures

Question 10

stages of neurocysticercosis

Answer 10

1) viable/vesciular: CSF intensity cysts, no enhancements; central dot (scolex)
2) colloidal: ring enhancing lesions; increased diffusivity
3) nodular/granlar: edema as cyst involutes, cyst wall thickens
4) calcified: parenchymal calcifications with small foci of susceptibility (GRE)

Question 11

racemose neurocystericercosis

Answer 11

variant without scolex

Question 12

intraventricular neurocysticercosis

Answer 12

typically aqueduct of Slyvius or 4th ventricle; obstructing cyst only visible on FLAIR

Question 13

toxoplasmosis

Answer 13

most common mass lesion in AIDS; CD4 < 100
parasite toxoplasma gondii

multiple ring enhancing lesions, typically basal ganglia with nodular enhancement

Question 14

ddx for toxoplasmosis

Answer 14

CNS lymphoma

toxo does not restrict diffusion and does not demonstrate increased CBV

toxo is hypometabolic on FDG PET and not avid on thallium

Question 15

viral CNS infections

Answer 15

herpes encephalitis, HIV encephalopathy, CMV encephalitis

Question 16

herpes encephalitis

Answer 16

HSV1; reactivation from trigeminal ganglion
fever, mesial temporal lobe signal abnormality, altered mental status

may have edema, hemorrhage, necrosis

PCR of HSV in CSF, lumbar puncture

Question 17

ddx for medial temporal lobe lesions

Answer 17

herpes encephalitis, MCA infarct, infiltrating glioma, limbic encephalitis, seizure-related changes

Question 18

HIV encephalopathy

Answer 18

most common CNS infection in AIDS; progressive neurodegenerative disease

diffuse cerebral atrophy and T2 prolongation in periventricular and deep white matter; spares subcortical U fibers

Question 19

CMV encephalitis

Answer 19

disease of immunosuppressed; CD4 < 50

ventriculitis or meningoencephalitis

subependymal FLAIR hyperintensity and enhancement throughout ventricular system

common TORCH infection in neonates&raquo_space; atrophy, encephalomalacia, ventricular enlargement, periventricular calcification

Question 20

creudtzfeldt jakob disease

Answer 20

neurodegenerative disease caused by prion

cortical ribonning with FLAIR hyperintensity and restricted diffusion of cortex; may also affect basal ganglia and thalami; motor cortex spared

Question 21

pulvinar sign

hockey stick sign

Answer 21

pulvinar: DWI and FLAIR signals in pulvinar nucleus of thalami

hockey stick: DWI/FLAIR signal in dorsomedial thalamus

Question 22

toxic/metabolic white matter changes

Answer 22

liver disease, hypoglycemia, hypoxic ischemic encephalopathy, methanol poisoning, carbon monoxide

Question 23

liver disease brain findings

Answer 23

hyperintense T1 signal in the globus pallidus/substantia nigra (manganese deposition?)

Question 24

hypoglycemia brain findings

Answer 24

bilateral T2 prolongation in gray matter (cortex, hippocampi, basal ganglia)

Question 25

hypoxic ischemic encephalopathy

Answer 25

circulatory/respiratory failure&raquo_space; global hypoxia/anoxia

gray matter (cerebral cortex/hppocampi, basal ganlia); worse prognosis if basal ganglia involved

white cerebellum sign (cerebellum hyperattenuating compared to supratentorial brain)

Question 26

methanol poisoning

Answer 26

optic neuritis; hemorrhagic necrosis of putamen/white matter edema

Question 27

carbon monoxid

Answer 27

T2 prolongation and restricted diffusion of globus pallidus