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Nervous System > CM- Neuroradiology > Flashcards

CM- Neuroradiology Flashcards

1
Q

In a CT through the posterior fossa and middle cranial fossa, what is anterior to the forth ventricle?
What is posterolateral?

A

The pons is anterior to the fourth ventricle and the cerebellar hemispheres are posterolateral to the forth ventricle.

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2
Q

What cisterns surround the pons at the level of the posterior foss and middle cranial fossa?
What vessel can be visualized at this level?

A 
Anterior = prepontine cistern [with the basilar trunk in it] 
Laterally = perimesencephalic cistern
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3
Q

In a CT at the level of the midbrain, what is seen anterior to the midbrain?
What is posterior?
What vessels can be seen at this level?

A

Anterior to the midbrain is the suprasellar cistern[with the optic chiasm visible]

Posterior to the midbrain is the quadrigeminal plate and the quadrigeminal plate cistern.

At this level, the MCA can be visualized in the sylvian fissure

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4
Q

What does the interpeduncular cistern merge with anteriorly?

A

the suprasellar cistern

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5
Q

What does the most cephalad aspect of the quadrigeminal plate cistern merge with anteriorly? Laterally?
What is posterior to the quadrigeminal plate cistern?

A

Anteriorly- aqueduct of sylvius

Laterally- ambien cistern

Posterior - superior vermian cistern

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6
Q

In a CT image at the level of the third ventricle and the foramina of Monro. What lies on either side of the 3rd ventricle?
What darker grey is seen even further lateral?

A

The thalamus flanks the third ventricle

Further laterally lie the posterior limbs of the internal capsule

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7
Q

What is cupped in the concavity of the frontal horns of the lateral ventricles?

A

caudate heads

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8
Q

At the level of the third ventricle, what cistern can be seen posteriorly?

A

cistern of Galen

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9
Q

What cisterns are seen behind the pulvinars of the thalami at the level where the calcified pineal gland is visible?

A

retrothalamic cisterns

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10
Q

What cisterns are located laterally to the putamen and globus pallidus [lentiform nuclei] ?

A

insular cistern

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11
Q

What can be visualized in the ventricular trigones of CT?

A

calcified glomus of the choroid plexus

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12
Q

At the level of CT where calcified choroid plexus is visible, and the corpus callosum spans the midline, what is the white matter referred to as?

A

Corona radiata

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13
Q

What is anterosuperior to the 3rd ventricle?

What is inferior?

A

It receives CSF from the lateral ventricles via the foramen of Monro.

Inferiorly, it opens up to the fourth ventricle via the aqueduct of sylvius.

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14
Q

What does the fourth ventricle open up to inferiorly?

A

foramina of Luschka and Madendie

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15
Q

What are the components of the lateral ventricles?
Which parts make up the trigone?
Which parts are most frequently asymmetric?

A
  1. frontal horns
  2. bodies
  3. temporal horns
  4. occipital horns

Temporal + occipital = trigones (atria) with calcified choroid plexus

Most frequently asymmetric = temporal [followed by occipital]

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16
Q

What are cisterns?

A

counterpart of the sulci- they are located around the base of the brain rather than over the convexities. They are in continuitiy with each other

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17
Q

What cistern is at the level of the internal auditory canals?

A

cerebello-pontine angle cistern

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18
Q

What cistern is most important for the early detection of small amounts of subarachnoid blood?

A

interpeducular cistern

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19
Q

What are the forebrain components of the basal ganglia?

A
  1. lentiform nucleus [globus pallidus, putamen]

2. caudate nucleus

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20
Q

White is the white matter tract at the level of the the lateral ventricles?
What is the white matter above the lateral ventricles?

A

At lateral ventricles- corona radiata

Above = centrum semiovale

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21
Q

What is the 4 step approach to Cranial CT?

A
  1. Evaluate the CSF spaces [ventricles, sulci, cisterns]
  2. Are there areas of asymmetry? [increased white, diminished dark]
  3. Contrast enhancement?
  4. Describe lesion characteristics if discovered
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22
Q

What is increased size of ventricles at the expense of sulci and cisterns?

A

Hydrocephalus

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23
Q

What pathology is associated with increased size of ventricles, sulci and cistern?

A

atrophy [volume loss of parenchyma]

24
Q

What pathology is associated with decreased size of ventricles, sulci and cisterns?

A

Diffuse edema

25
Q

What pathology is associated with focal attenuation of sulci or ventricles?

A

focal mass or mass-like lesion

26
Q

What will happen to the brain if there is:

  1. volume loss in a given hemisphere
  2. volume increase in a given hemisphere
A
  1. Loss= ipsilateral shift of the midline [chronic infarct]

2. Gain = mass effect–>contralateral shift

27
Q

What 4 situations would increase density on a CT? [bright white]

A
  1. recent hemorrhage
  2. calcium
  3. bone
  4. contrast agent
28
Q

What 5 situations would decrease density on a CT?

A
  1. vasogenic edema - white matter w/masses
  2. cytotoxic edema- white and gray w/ ischemia
  3. encephalomalacia [atrophy of brain parenchyma]
  4. gliosis- fibrotic brain parenchyma
  5. chronic hematoma
29
Q

What 5 things will be positive for contrast enhancement on CT?

A
  1. neoplasm [primary benign, primary malignant, secondary]
  2. infections [absesses]
  3. vascular lesions [AVMs]
  4. Ischemia- subacute
  5. active demyelination
30
Q

What 4 things will be negative for contrast enhancement on CT?

A
  1. chronic ischemia
  2. low grade neoplasm
  3. quiescent demyelination
  4. progressive multifocal leukoencephalopathy
31
Q

You have discovered a lesion on CT. What 5 characteristics should be evaluated?

A
  1. parenchymal vs. extraparenchymal
  2. margination [well circumscribed = benign]
  3. density
  4. contrast enhancement, nodular [lymphoma], ring-like [abscess] , patchy [ischemia]
  5. effect on adjacent structures
32
Q

What are the 4 types of intracranial hematomas?

A
  1. parenchymal
  2. subarachnoid
  3. subdural
  4. epidural
33
Q

Describe the effect of acute hematomas on midline.
Are they hyper or hypodense?
What can they be surrounded by?

A

They have mass effect and shift the midline to the contralateral direction [or focally attenuate the CSF space]

They are hyperdense [Bright white] and gradually progress to hypodense [black] over the course of several weeks.

They can sometimes be surrounded by a zone of hypodense edema

34
Q

A hyperdense lesion is caused by what 4 things?

What could give you clues that it is an acute bleed?

A
  1. acute bleed= irregular smooth border, edema surrounding it, asymmetry, loss of CSF space
  2. calcium
  3. bone
  4. contrast
35
Q

How does subarachnoid hemorrhage appear on CT?
How does the midline shift?
Where is it best appreciated?

A

high density fluid occupying a normally low dense CSF space.
The midline does NOT shift with subarachnoid hemorrhage.

It is best appreciated in the basal cisterns [esp. interpeducular cistern and lamina terminalis]

36
Q

Subarachnoid hemorrhage often presents with what 2 accompanying phenomenon?

A
  1. intraventricular blood

2. hydrocephalus [due to meningitis obstruction of extraventricular CSF or intraventricular obstruction by blood clot]

37
Q

What are the 2 most common causes of subarachnoid hemorrhage?

A
  1. aneurysm- in circle of willis [ant comm artery, posterior comm artery, MCA bifurcation, ICA bifurcation, basilar apex, PICA]
  2. trauma
38
Q

Describe a subarachnoid lesion of the MCA region.

A

Hyperdense round lesion
Surrounding edema
Hyperdense material tracking into multiple cisterns

39
Q

Describe the CSF spaces, asymmetry, and lesion associated with a giant basilar apex aneurysm.

A

CSF: dilated lateral ventricles at the expense of sulci

Assymetry: because the lesion is in the center, the overall picure is symmetric

Lesion: round density in the prepontine cistern [sellar region] displacing the pons posteriorly

40
Q

You are examining a CT and note that a lesion extends across suture lines and occupy a large surface area. The lesion is not able to cross the midline.
There is blood of varying density within the collection. The contralateral lateral ventricle is dilated.
What does this presentation make you suspicious of?

A

Subdural hematoma:

-crosses midline not center because of double reflection of the dura [falx cerebri]

41
Q

What is a reliable factor for distinguishing subdural from epidural collections of blood?

A

Subdural extends across the coronal suture

42
Q

When examining a CT, you note an elliptoid lesion exerting mass effect with attenuation of sulci and ventricles, and a contra-lateral midline shift. The lesion does NOT extend across suture lines.
What type of hemorrhage is this likely to be?

A

Epidural

43
Q

What brain bleed is most associated with skull fractures?

A

Epidural has a closer correlation than subdurals

44
Q

What are the 3 “mechanisms” of infarct?

A
  1. thrombosis
  2. embolism
  3. hypoperfusion
45
Q

Describe the effects of an acute infarct on the brain.

A
  1. mass effect - effacement of sulci and ventricles with contralateral midline shift
  2. density mildly decreased [darker]
  3. cytotoxic edema is present
  4. contrast enhancement is absent
46
Q

Describe a subacute infarct on CT.

A

Vascular, leptomeningeal, parenchymal enhancement seen 3 days to 3 wks from the event

47
Q

How can you differentiate an acute and subacute infarction?

A

subacute infarcts will enhance

Acute will not

48
Q

Describe a chronic infarct on CT.

A
  1. marked hypodensity
  2. volume loss –> ipsilateral midline shift
  3. NO contrast enhancement
  4. enlargement of ipsilateral lateral ventricle
49
Q

What is an example of a benign extra-parenchymal mass?

Where will it be localized on a CT?

A

Meningioma -localized to the periphery on a CT exerting mass effect on adjacent sulci.
Increased density, areas of calcification

50
Q

You are examining a CT and see a well-circumscribed hyperdense mass with a focus of globular calcification. It is right near the surface of the skull. The patient history is that of gradual neurological decline. What is the likely diagnosis?

A

Meningioma - abutting the surface of the skull is a clue that the lesion is extra-parenchymal

51
Q

On CT you note mass effect with attenuation of adjacent sulci and ventricles. There are patchy areas of increased density surrounded by zones of hypodense edema. Contrast enhancement is nodular and peripheral.
What is the likely diagnosis?

A

Mets or primary CNS cancer

52
Q

A ring-enhancing lesion on CT suggests what 2 things?

A
  1. abscess

2. neoplasm

53
Q

What 2 things cause hydrocephalus?

A
  1. obstruction to CSF pathways

2. overproduction of CSF

54
Q

What is the difference between communicating and non-communicating hydrocephalus?

A

Communicating = obstruction is distal to the fourth ventricle outlets [luschka and magendie]

Non-communicating = proximal to the foramina of luschka and magendie

55
Q

On CT you note a lesion that is exerting mass effect with attenuation of sulci and ventricles with a contralateral midline shift.
The lesion has a hypodense center and the peripheral wall is slightly more dense.
After contrast enhancement, there is marked enhancement of the wall [which is less developed along the ventricle margin.

What is the most likely diagnosis?

A

Abscess

56
Q

How does cysticercosis present on CT?

A
  • One or more small cystic areas

- some may have a scolex seen as a focus of density in the lesion

Nervous System (32 decks)

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