Neuroimaging

Question 1

Indications for Skull X-ray

5

Answer 1

1. When they are not otherwise getting a CT Scan (A&O x 3, GCS 15) and: Suspect skull fracture, sinusitis, facial bone tumors, nose pathology, foreign Body
2. Evaluation for fractures of the mandible and maxilla
3. Evaluation of the skull for lytic lesions such as in multiple myeloma
4. Scalp has full thickness laceration or boggy hematoma (looking for skull fracture)
5. To evaluate for scalp foreign bodies such as glass

Question 2

The major drawbacks to skull x-rays

3

Answer 2

1. Lack detail

2. No reassurance if negative in the setting of trauma as unable to evaluate intracranial contents

3. Unable to see fractures in the skull base, if basilar skull fracture suspected a CT scan is indicated

Question 3

What are lytic lesions called?

Answer 3

punched out lesions because of decreased bone density

Question 4

What helps differentiate fractures and blood vessels?

Answer 4

When youre wondering if somehting is a fracture or a vessel. If youre branching then its a vessel. If its more straight its a fractire

Question 5

What could iodine based contrast cause?

Answer 5

ATN

Question 6

CT Inidcations

4

Answer 6

1. Evaluation of the skull and skull base, vertebrae
2. Evaluation of the ventricles
3. Suspicion of intracranial masses, mass effects
4. Looking for acute hemorrhage, ischemia

ischemia is not evident on CT scan until about 24 hours post onset of symptoms

Question 7

Describe what the following might show us using CT on evaluation:

1. Evaluation of the skull and skull base, vertebrae? 2
2. Evaluation of the ventricles? 3
3. Suspicion of intracranial masses, mass effects? 3
4. Looking for acute hemorrhage, ischemia? 2

Answer 7

1.

• trauma
• bone lesions

2.

• hydrocephalus,
• shunt placement

3.

• headache,
• N/V,
• visual symptoms

4.

• stroke,
• mental status change

Question 8

1. Ischemia is not evident on CT scan until when?
2. So why is CT our first inital test?

Answer 8

1. about 24 hours post onset of symptoms
2. CT to rule out hemorrhagic stroke. cant tell us ischemic

Question 9

IV Contrast in Head CT: Yes or No?

No: 7

Yes: 4

Answer 9

Without contrast:

1. Trauma
2. R/O stroke
3. R/O hemorrhage
4. Hydrocephalus
5. Dementia
6. Epilepsy
7. Congenital malformations

With contrast

1. Neoplasm (usually very vascular)- usually doing MRI with this anyway
2. Infection
3. Vascular disease
4. Inflammatory disease

Question 10

Interpreting a CT Scan of the Head for PA’s

4 steps. What are they?

Answer 10

1. Look for fluid
2. Look for mass
3. Look for shift
4. Look at each side and compare

Question 11

1. The more dense the tissue, the ______it looks on CT?
2. Any calcified structure (like the skull) appears ______?
3. New hemorrhage in the brain is _____?
4. Water (or CSF) looks _____on CT

Answer 11

1. brighter
2. bright
3. also bright
4. dark

Question 12

1. What is a subarachnoid hemorrhage?
2. Where is it at?
3. What is a subdural hematoma and where is it at?
4. What is an epidural hematoma and where is it at?
5. WHat is a epidural hematoma associated with?

Answer 12

Subarachnoid hemorrhage (see picture-layered out on the surface of the brain)

1. Arterial bleeding on the surface of the brain
2. Between the pia mater and the arachnoid mater

Subdural hematoma

3. Venous bleeding between the arachnoid and the dura mater

Epidural hematoma

4. Dural artery or venous sinus bleeding between the skull and dura
5. Associated with skull fracture

Question 13

1. SAH: What is the injury to?
2. Where do the ruptured vessels bleed?

Answer 13

1. Injury of small arteries or veins on the surface of the brain
2. Ruptured vessel bleeds into the space between the pia and arachnoid mater

Question 14

Causes of subarachnoid hemorrhage

2

(most common)?

Answer 14

1. Trauma

Most common cause

2. Ruptured cerebral aneurysm

Question 15

What (arrowheads) fills the sulci over the
right cerebral convexity in this subarachnoid hemorrhage?

See Picture

Answer 15

High density blood

Question 16

1. What is the injury to in a subdural hematoma?
2. Where does blood collect?

Answer 16

1. Tearing of bridging veins from deceleration and acceleration or rotational forces
2. Blood collects in the space between the arachnoid mater and the dura mater

Question 17

Subdural Hematoma CT has the following characteristics: 3

Answer 17

1. Crescent shaped
2. Hyperdense, may contain hypodense foci due to serum, CSF or active bleeding
3. Does not cross dural reflections

Question 18

High density, crescent shaped hematoma (arrowheads)
overlying the right cerebral hemisphere. Whats important to note in this image?

Question 19

Subacute subdural hematoma (arrowheads). Whats important to note about this CT?

Answer 19

Note the compression of
gray and white matter in the left hemisphere due to the mass effect.

Question 20

Chronic Subdural hematoma: Whats importnat to notice in this CT?

Crescent shaped chronic subdural hematoma (arrowheads)

Answer 20

Notice
the low attenuation due to reabsorbtion of the hemorrhage over time.

Question 21

1. Epidural hematoma is usually associated with what?
2. What is the injury that results from this?
3. Where does the blood collect?

Answer 21

1. Usually associated with a skull fracture
2. The fractured bone lacerates a dural artery or a venous sinus
3. The blood from the ruptured vessel collects between the skull and dura

Question 22

1. On the CT, the hematoma forms a what?
2. It is usually uniformly ____ _______but may contain hypodense foci due to active bleeding.

Answer 22

1. hyperdense biconvex mass
2. high density

Question 23

Describe the differences:

Epidural vs Subdural

2

Answer 23

See picture

Question 24

Describe the following for Epidural, Subdural and Subarachnoid:

1. In relation to the dura
2. Respects suture lines?
3. Trauma?
4. What kind of blood and usually from where?
5. Shape on CT?
6. Clinical presentation?

Answer 24

Epidural

1. Above the dura
2. Respects suture lines
3. High force trauma
4. Arterial blood (commonly the middle meningeal artery)
5. Lentiform (lens-shaped) or biconcave on CT
6. Acute presentation

Subdural

1. Below the dura
2. Doesn’t respect suture lines
3. Low force trauma
4. Venous (from venous plexus)
5. Cresent (banana-shaped) on CT
6. May be insidious (worsening headache over days)

Subarachnoid

1. Below the arachnoid
2. No respect for anything
3. Aneurysm rupture or high force trauma
4. Arterial from the circle of Willis
5. Lining surface, going into fissures and sulci and sella (death-star)
6. Acute presentation (thunderclap headache)

Question 25

Describe the difference on CT of a ischemic stroke and hemorrhagic stroke

Answer 25

Initial non-contrast head CT scans of two patients with stroke presenting with left-sided weakness. The patient in (A.) has an ischemic stroke in the right hemisphere which is not yet visible on CT imaging early after onset while the patient in (B.) has evidence of a right hemisphere intracerebral hemorrhage.

Question 26

What is this and why do you think so?

Answer 26

Figure 1: Acute intracerebral hematoma within the right temporal lobe (arrow) with surrounding edema (E). 60 year-old patient with melanoma. Hemorrhage is from metastatic tumor bleed.

Question 27

CT can detect acute intracerebral blood as small as\_\_\_mm, due to what?

Answer 27

1. 2 2. contrast between high-density of blood and low-density of surrounding brain (arrows).

Question 28

What is this and why do you think so?

Answer 28

Acute subdural hematoma covering the right cerebral hemisphere (arrows), more prominent posteriorly. Patient with history of recent fall.

Question 29

What is this and why do you think so?

Answer 29

Subarachnoid Blood Subarachnoid blood is recognized by visualizing the high-density of acute blood outlining the cerebral sulci and subarachnoid cisterns. Subarachnoid blood filling the right cerebral sulci (arrow), related to recent pituitary surgery

Question 30

What is this and why do you think that?

Answer 30

Epidural hematoma: ## Footnote Bone fracture on the bone window gives it away. Usually due to the fracture

Question 31

CT Angiography indications 7

Answer 31

1. Atherosclerosis 2. Thromboembolism 3. Vascular dissection 4. Aneurysms 5. Vascular Malformations 6. Penetrating trauma 7. Evaluation of carotids

Question 32

What is the biggest risk in MRI?

Answer 32

Risk of dislodging tissue with imbedded metal

Question 33

Most common types of MR images are what (and describe them) and what are the differences?

Answer 33

1. T1-weighted MR images- useful to look at normal anatomy of the brain 2. T2-weight MR images - useful to look at abnormal processes (or pathology) in the brain 3. The difference between the two are different pulse sequences

Question 34

What is bright and dark on a T1: 1. Fat? 2. White matter? 3. CSF?

Answer 34

1. Fat is bright 2. White matter (inner part of brain) is brighter than gray matter (cortex or outer part of the brain) 3. Water (CSF) is dark

Question 35

What is bright and dark on a T2: 1. Water? 2. Blood? 3. White matter?

Answer 35

1. Water is bright 2. Blood is bright 3. White matter is darker than gray matter

Question 36

Indications for MRI 7

Answer 36

1. Subacute and chronic hemorrhages 2. Cerebral infarct (stroke)-NOT ACUTE. Do the CT first then the MRI the next day. 3. Primary and metastatic brain tumors 4, Intracranial abscess 5. Multiple sclerosis and other demyelinating diseases 6. New onset or refractory seizures 7. Vasculitis

Question 37

MRI in Head Trauma: 1. MRI is superior to CT for every pathology except what? 2 2. Much superior for what? 4 3. Less advantageous? 2

Answer 37

1. - skull fracture - acute subarachnoid hemorrhage 2. - edema, - contusions and - hematomas - posterior fossa lesions 3. - Speed of study and cost - Improved data does not impact clinical care

Question 38

What is this?

Answer 38

Subdural Hematoma on MRI

Question 39

What is this?

Answer 39

Diagnosis: Acute one day old infarction involving the right middle cerebral artery (MCA) territory.

Question 40

What is this?

Answer 40

Pituitary adenoma

Question 41

CT advantages? 5 CT disadvantages? 2

Answer 41

CT Advantages 1. Simpler, cheaper, more accessible 2. Tolerated by claustrophobics 3. No absolute contraindications 4. Fewer pitfalls in interpretation 4. Better than MR for bone detail CT Disadvantages 1. IV contrast complications 2. Ionizing radiation

Question 42

MRI advanatages? 3 MRI disadvantages? 6

Answer 42

MRI Advantages 1. Much broader palette of tissue contrasts (including functional and molecular) yields greater anatomic detail and more comprehensive analysis of pathology 2. No ionizing radiation 3. IV contrast better tolerated 4. Better for tumor evaluation MRI Disadvantages 1. Higher cost, limited access 2. Difficult for unstable patients 3. Several absolute contraindications (cardiac pacer, some aneurysm clips, etc.) 4. Claustrophobics may need sedation 5. Image interpretation more challenging 6. Lacks bone detail

Question 43

MR Angiography is useful fro the evaluation of what?

Answer 43

intracerebral blood vessels

Question 44

MRI is preferred over CT but brain CT is suitable to exclude what? 4

Answer 44

1. mass lesion, 2. hemorrhage or 3. stroke or 4. if MRI is unavailable

Question 45

What is the gold standard for imaging the carotid arteries and evaluating cerebral aneurysms after subarachnoid hemorrhage?

Answer 45

Cerebral angiography (definitive! first test is MRI)

Question 46

More Indications for MR angiography? 5

Answer 46

1. Cerebral Vasculitis 2. Small Aneurysms 3. AVM’s 4. Intraarterial treatment of cerebral vasospasm 5. Treatment of aneurysm or AVMs

Question 47

What imaging study is most appropriate for acute stroke? What are the limitations?

Answer 47

CT Can't see ischemia immediately

Question 48

1. What imaging study is most appropriate in a patient with a full thickness scalp laceration and a GCS of 15 (normal)? 2. If there is a concern for a tumor what is the most appropriate study? 3. If there is a concern for aneurysm what is the most appropriate study(s) to order? 4. In a patient with new onset seizures what is the diagnostic test of choice and what is the initial imaging test of choice?

Answer 48

1. skull xray 2. MRI 3. MRI 4. worries about tumor so MRI