Neuro Imaging

Question 1

What are the advantages for CT?

Answer 1

Fast = excellent for trauma situations and quick for detecting brain bleeds
Skull and facial bone imaging for fracture

Question 2

What are the disadvantages for CT?

Answer 2

Lower resolution on soft tissue/brain

Cannot detect acute ischemic strokes

Question 3

Describe an epidural hematoma

Answer 3

Faster arterial bleed outside of the dura (middle meningeal A rupture due to skull fracture)
Dura separating from skull but dura is strongly attached at sutures (does not cross)
Forms elliptical shape/lemon/lens
Classic history: head trauma -> unconscious -> lucid interval -> loss of mental status (pressure)

Question 4

Describe a subdural hematoma

Answer 4

Rapid change in velocity -> stretch damages bridging veins under the dura
Common in elderly pts due to reduced brain volume increasing strain on veins
Blood not restricted by sutures but limited by falx cerebri (wider spread)
Crescent shape/banana
Increase pressure -> brain herniation

Question 5

What are the advantages of MRI?

Answer 5

Highest resolution
Adds sagittal plane view
Very good for defining and differentiating structure/soft tissue lesions (can use different sequences)

Question 6

What are the disadvantages for MRI?

Answer 6

Slow imaging technique, claustrophobic situation
No metal implants (aneurysm clips okay)
Sensitive to movement (movement artifact)
Not as good at imaging bone lesions

Question 7

Describe MRI sequences

Answer 7

Changing the sequence will change color of tissue/fluids producing contrast between different structures
Protons in different tissues have unique realignment periods
Change by repetition time (TR - time b/w RF pulses)
Time echo (TE - time b/w RF pulse and receipt energy from protons)

Question 8

Describe T1 MRI sequences

Answer 8

T1 image looks like normal anatomy (white matter is white and gray matter is gray)
Good for assessing anatomy/soft tissue tumors
Easy to see disruption of BBB by contrast leak

Question 9

Describe T2 weighted MRI sequences

Answer 9

Opposite of T1 (white matter is dark now)
Indication: good for seeing demyelination
Con: difficult to visualize inflammation next to ventricle
CSF and inflammation will be bright

Question 10

Describe T2 flair MRI sequences

Answer 10

FLAIR = fluid attenuated inversion recovery
Modified T2 image: similar contrast to regular T2 but CSF appears dark
Indication: checking for inflammation near ventricles
CSF is dark and inflammation is bright

Question 11

Describe contrast used for MRI and CT

Answer 11

Used to find things that disrupt the BBB (normal brain will not appear different)
CT uses iodine based contrast
MRI uses gadolinium based contrast
Both types can cause kidney injury

Question 12

Describe angiography?

Answer 12

Indications: Stroke/TIA, aneurysm or vascular malformations
Used to view brain vasculature and neck vasculature
Done by Fluoroscopy, CT or MRI
Use of contrast can cause kidney damage

Question 13

Describe functional MRI

Answer 13

Maps out brain activity
Detects changes in blood flow (blood flow associated with neuronal activation, regions responding to different stimuli, regions executing different tasks)
Used mostly for research with some clinical use

Question 14

What are the other imaging modalities for neuro complaints?

Answer 14

Fluoroscopy, myelography, ultrasound, carotid ultrasound, ultrasound guided procedures

Question 15

Describe fluoroscopy

Answer 15

Swallow study
Pt swallows radio-opaque material (barium slurry)
Swallowing is recorded by video and analyzed to determine issues with swallowing
Commonly used if pt is having problems swallowing due to neurologic weakness

Question 16

Describe myelography

Answer 16

Dye is injected below the dura (intrathecal) and imaged by fluoroscopy
Helps visualize space b/w nerves and structures around it (spinal stenosis/herniated discs, masses on SC, spondylosis/arthritis)
Uncommon modality, mostly replaced by CT/MRI

Question 17

Describe ultrasound

Answer 17

Uses ultrasound echolocation to produce image
Able to differentiate soft tissue structures well
Indications: point of care ultrasound for quick diagnosis and guiding procedures

Question 18

Describe carotid ultrasound

Answer 18

Used to assess arterial supply to the brain
After transient ischemic attack or ischemic stroke
Assess for carotid stenosis (plaque build up -> clots)

Question 19

Describe ultrasound guided procedures

Answer 19

Easy bed side needle guidance
Commonly used to target nerves for procedures (steroids)
Nerve blocks for surgery (local anesthesia)

Question 20

Describe electroencephalogram (EEG)

Answer 20

Non invasive way to measure electrical signals of brain
Electrodes placed on pts scalp and observe changes in signal pattern
Used for diagnosing and monitoring seizure disorders

Question 21

Describe an electromyogram (EMG)

Answer 21

Measures electrical conduction in nerves and muscles
Nerve conduction study and needle electrode exam
Diagnoses and maps out nerve injury (paresthesia, carpal tunnel, radiculopathy)

Question 22

What is a fluoroscein stain?

Answer 22

Used to detect injury to the cornea

Injured corneal tissue will shine bright green

Question 23

What is the primary indication for fluoroscopy/swallow study?

Answer 23

Difficulty swallowing

Question 24

What is the primary indication for myelography?

Answer 24

Spinal nerve impingement/spondylosis

Question 25

What is the primary indication for ultrasound?

Answer 25

Carotid artery stenosis/needle guidance to nerves

Question 26

What is the primary indication for an EEG?

Answer 26

Confirming seizure activity

Question 27

What is the primary indication for an EMG?

Answer 27

Assessing peripheral nerves and muscles

Question 28

What is the primary indication for a fluoroscein stain?

Answer 28

Corneal damage