Imaging the Brain

Question 1

T1 pulse sequence

Answer 1

good for anatomic detail

fluid: black
poor distinction between gray and white matter

Question 2

T1 + C pulse sequence

Answer 2

highlights vascular structures
ID disruptions in BBB

contrast enhancing: bright (abnormal)
non-contrast enhancing: dark

Question 3

T2 pulse sequence

Answer 3

identifying fluid

fluid: bright

Question 4

FLAIR pulse sequence

Answer 4

determining fluid type

normal (CSF): dark
abnormal: bright

Question 5

T2* pulse sequence

Answer 5

identifying hemorrhage

blood: dark

Question 6

when to use CT over MRI

Answer 6

cranial and extra cranial structures

skull, nasal cavity, oral cavity, musculature

Question 7

when to use MRI over CT

Answer 7

intercranial structures

brain, brainstem, nerves, etc

Question 8

causes of edema in the brain

Answer 8

1. cell damage –> damaged proton pumps –> water enters cells –> cells swell
2. BBB damage –> water enters –> tissue swells

Question 9

types of CNS edema

Answer 9

1. cytotoxic
2. hydrostatic
3. vasogenic

Question 10

cytotoxic edema

Answer 10

intracellular edema from Na/K pump dysfunction

characteristics:
- GM and WM
- cell swells from ischemia

Question 11

hydrostatic edema

Answer 11

extracellular edema from pressure

characteristics:
- surrounds ventricles
- causes obstructive hydrocephalus

Question 12

vasogenic edema

Answer 12

extracellular edema from disruption of BBB

characteristics:
- WM
- high protein edema leaks through loose tight junctions

Question 13

signs of mass/mass effect

Answer 13

1. mass (asymmetric)
2. midline shift
3. edema
4. thinning of sulci/gyri
5. ventricular obstruction
6. herniation

Question 14

causes of intraventricular hydrocephalus

Answer 14

1. obstruction of CSF flow
2. overproduction of CSF

Question 15

herniation

Answer 15

increased pressure in the cranial cavity causes the brain parenchyma to displace:
1. transtentorial
2. subfalcine
3. foraminal

Question 16

transtentorial/subtentorial herniation

Answer 16

cerebrum herniates caudally over the tentorium cerebelli

Question 17

subfalcine herniation

Answer 17

one side of cerebrum herniates over the falx cerebri to the other side

Question 18

foraminal herniation

Answer 18

cerebellum herniates caudally through the foramen magnum

Question 19

what are the 3 contributors to normal ICP

Answer 19

1. blood
2. CSF
3. brain parenchyma

Question 20

what causes an increase in ICP

Answer 20

masses
edema/inflammation
obstruction/overproduction of CSF
hemorrhage

Question 21

major categories of CNS disease

Answer 21

1. vascular
2. metabolic/toxic
3. inflammatory
4. neoplastic

Question 22

vascular CNS disease imaging

Answer 22

multiple/recurring dark areas on T2* sequence

resolves with time via resorption

Question 23

metabolic/toxic CNS disease imaging

Answer 23

bilaterally symmetric lesions

Question 24

categories of inflammatory CNS disease

Answer 24

1. infectious
2. non-infectious

Question 25

infectious CNS disease imaging

Answer 25

T1 + C

peripherally enhancing rim with dark center (pus/necrosis)

if meningitis: contrast enhancing meninges with subdural fluid

Question 26

non-infectious CNS disease imaging

Answer 26

GME: white matter
NME: gray matter + subcortical white matter
LE: white matter of brainstem and cerebrum

Question 27

common CNS neoplasia locations

Answer 27

• astrocytic
• choroid plexus
• meningeal
• tumors from cranial/skull base

Question 28

intra-axial neoplasia

Answer 28

arises from within brain parenchyma

• brain surrounds entire mass
  ex. astrocytoma

Question 29

extra-axial neoplasia

Answer 29

arises from outside the brain parenchyma

• has one flat side attaches to skull/meninges
  ex. pituitary tumor, meningioma

Question 30

intraventricular

Answer 30

arises from within the ventricles

ex. choroid plexus tumor

Question 31

neoplastic CNS disease imaging

Answer 31

brightly contrast enhancing

may have peripheral contrast enhancing rim with dark center