Neuroimaging Flashcards
Indications for Skull X-ray
5
- 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
- Evaluation for fractures of the mandible and maxilla
- Evaluation of the skull for lytic lesions such as in multiple myeloma
- Scalp has full thickness laceration or boggy hematoma (looking for skull fracture)
- To evaluate for scalp foreign bodies such as glass
The major drawbacks to skull x-rays
3
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
What are lytic lesions called?
punched out lesions because of decreased bone density
What helps differentiate fractures and blood vessels?
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
What could iodine based contrast cause?
ATN
CT Inidcations
4
- Evaluation of the skull and skull base, vertebrae
- Evaluation of the ventricles
- Suspicion of intracranial masses, mass effects
- Looking for acute hemorrhage, ischemia
ischemia is not evident on CT scan until about 24 hours post onset of symptoms
Describe what the following might show us using CT on evaluation:
- Evaluation of the skull and skull base, vertebrae? 2
- Evaluation of the ventricles? 3
- Suspicion of intracranial masses, mass effects? 3
- Looking for acute hemorrhage, ischemia? 2
1.
- trauma
- bone lesions
2.
- hydrocephalus,
- shunt placement
3.
- headache,
- N/V,
- visual symptoms
4.
- stroke,
- mental status change
- Ischemia is not evident on CT scan until when?
- So why is CT our first inital test?
- about 24 hours post onset of symptoms
- CT to rule out hemorrhagic stroke. cant tell us ischemic
IV Contrast in Head CT: Yes or No?
No: 7
Yes: 4
Without contrast:
- Trauma
- R/O stroke
- R/O hemorrhage
- Hydrocephalus
- Dementia
- Epilepsy
- Congenital malformations
With contrast
- Neoplasm (usually very vascular)- usually doing MRI with this anyway
- Infection
- Vascular disease
- Inflammatory disease
Interpreting a CT Scan of the Head for PA’s
4 steps. What are they?
- Look for fluid
- Look for mass
- Look for shift
- Look at each side and compare
- The more dense the tissue, the ______it looks on CT?
- Any calcified structure (like the skull) appears ______?
- New hemorrhage in the brain is _____?
- Water (or CSF) looks _____on CT
- brighter
- bright
- also bright
- dark
- What is a subarachnoid hemorrhage?
- Where is it at?
- What is a subdural hematoma and where is it at?
- What is an epidural hematoma and where is it at?
- WHat is a epidural hematoma associated with?
Subarachnoid hemorrhage (see picture-layered out on the surface of the brain)
- Arterial bleeding on the surface of the brain
- Between the pia mater and the arachnoid mater
Subdural hematoma
- Venous bleeding between the arachnoid and the dura mater
Epidural hematoma
- Dural artery or venous sinus bleeding between the skull and dura
- Associated with skull fracture
- SAH: What is the injury to?
- Where do the ruptured vessels bleed?
- Injury of small arteries or veins on the surface of the brain
- Ruptured vessel bleeds into the space between the pia and arachnoid mater
Causes of subarachnoid hemorrhage
2
(most common)?
- Trauma
Most common cause
- Ruptured cerebral aneurysm
What (arrowheads) fills the sulci over the
right cerebral convexity in this subarachnoid hemorrhage?
See Picture
High density blood
- What is the injury to in a subdural hematoma?
- Where does blood collect?
- Tearing of bridging veins from deceleration and acceleration or rotational forces
- Blood collects in the space between the arachnoid mater and the dura mater
Subdural Hematoma CT has the following characteristics: 3
- Crescent shaped
- Hyperdense, may contain hypodense foci due to serum, CSF or active bleeding
- Does not cross dural reflections
High density, crescent shaped hematoma (arrowheads)
overlying the right cerebral hemisphere. Whats important to note in this image?
Subacute subdural hematoma (arrowheads). Whats important to note about this CT?
Note the compression of
gray and white matter in the left hemisphere due to the mass effect.
Chronic Subdural hematoma: Whats importnat to notice in this CT?
Crescent shaped chronic subdural hematoma (arrowheads)
Notice
the low attenuation due to reabsorbtion of the hemorrhage over time.
- Epidural hematoma is usually associated with what?
- What is the injury that results from this?
- Where does the blood collect?
- Usually associated with a skull fracture
- The fractured bone lacerates a dural artery or a venous sinus
- The blood from the ruptured vessel collects between the skull and dura
- On the CT, the hematoma forms a what?
- It is usually uniformly ____ _______but may contain hypodense foci due to active bleeding.
- hyperdense biconvex mass
- high density
Describe the differences:
Epidural vs Subdural
2
See picture
Describe the following for Epidural, Subdural and Subarachnoid:
- In relation to the dura
- Respects suture lines?
- Trauma?
- What kind of blood and usually from where?
- Shape on CT?
- Clinical presentation?
Epidural
- Above the dura
- Respects suture lines
- High force trauma
- Arterial blood (commonly the middle meningeal artery)
- Lentiform (lens-shaped) or biconcave on CT
- Acute presentation
Subdural
- Below the dura
- Doesn’t respect suture lines
- Low force trauma
- Venous (from venous plexus)
- Cresent (banana-shaped) on CT
- May be insidious (worsening headache over days)
Subarachnoid
- Below the arachnoid
- No respect for anything
- Aneurysm rupture or high force trauma
- Arterial from the circle of Willis
- Lining surface, going into fissures and sulci and sella (death-star)
- Acute presentation (thunderclap headache)
Describe the difference on CT of a ischemic stroke and hemorrhagic stroke
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.
What is this and why do you think so?
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.
CT can detect acute intracerebral blood as small as___mm, due to what?
- 2
2.
contrast between high-density of blood and low-density of surrounding brain (arrows).
What is this and why do you think so?
Acute subdural hematoma covering the right cerebral hemisphere (arrows), more prominent posteriorly.
Patient with history of recent fall.
What is this and why do you think so?
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
What is this and why do you think that?
Epidural hematoma:
Bone fracture on the bone window gives it away. Usually due to the fracture
CT Angiography indications
7
- Atherosclerosis
- Thromboembolism
- Vascular dissection
- Aneurysms
- Vascular Malformations
- Penetrating trauma
- Evaluation of carotids
What is the biggest risk in MRI?
Risk of dislodging tissue with imbedded metal
Most common types of MR images are what (and describe them) and what are the differences?
- T1-weighted MR images- useful to look at normal anatomy of the brain
- T2-weight MR images - useful to look at abnormal processes (or pathology) in the brain
- The difference between the two are different pulse sequences
What is bright and dark on a T1:
- Fat?
- White matter?
- CSF?
- Fat is bright
- White matter (inner part of brain) is brighter than gray matter (cortex or outer part of the brain)
- Water (CSF) is dark
What is bright and dark on a T2:
- Water?
- Blood?
- White matter?
- Water is bright
- Blood is bright
- White matter is darker than gray matter
Indications for MRI
7
- Subacute and chronic hemorrhages
- Cerebral infarct (stroke)-NOT ACUTE. Do the CT first then the MRI the next day.
- Primary and metastatic brain tumors
4, Intracranial abscess
- Multiple sclerosis and other demyelinating diseases
- New onset or refractory seizures
- Vasculitis
MRI in Head Trauma:
- MRI is superior to CT for every pathology except what? 2
- Much superior for what? 4
- Less advantageous? 2
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
What is this?
Subdural Hematoma on MRI
What is this?
Diagnosis: Acute one day old infarction involving the right middle cerebral artery (MCA) territory.
What is this?
Pituitary adenoma
CT advantages? 5
CT disadvantages? 2
CT Advantages
- Simpler, cheaper, more accessible
- Tolerated by claustrophobics
- No absolute contraindications
- Fewer pitfalls in interpretation
- Better than MR for bone detail
CT Disadvantages
- IV contrast complications
- Ionizing radiation
MRI advanatages? 3
MRI disadvantages? 6
MRI Advantages
- Much broader palette of tissue contrasts (including functional and molecular) yields greater anatomic detail and more comprehensive analysis of pathology
- No ionizing radiation
- IV contrast better tolerated
- Better for tumor evaluation
MRI Disadvantages
- Higher cost, limited access
- Difficult for unstable patients
- Several absolute contraindications (cardiac pacer, some aneurysm clips, etc.)
- Claustrophobics may need sedation
- Image interpretation more challenging
- Lacks bone detail
MR Angiography is useful fro the evaluation of what?
intracerebral blood vessels
MRI is preferred over CT but brain CT is suitable to exclude what? 4
- mass lesion,
- hemorrhage or
- stroke or
- if MRI is unavailable
What is the gold standard for imaging the carotid arteries and evaluating cerebral aneurysms after subarachnoid hemorrhage?
Cerebral angiography (definitive! first test is MRI)
More Indications
for MR angiography? 5
- Cerebral Vasculitis
- Small Aneurysms
- AVM’s
- Intraarterial treatment of cerebral vasospasm
- Treatment of aneurysm or AVMs
What imaging study is most appropriate for acute stroke?
What are the limitations?
CT
Can’t see ischemia immediately
- What imaging study is most appropriate in a patient with a full thickness scalp laceration and a GCS of 15 (normal)?
- If there is a concern for a tumor what is the most appropriate study?
- If there is a concern for aneurysm what is the most appropriate study(s) to order?
- In a patient with new onset seizures what is the diagnostic test of choice and what is the initial imaging test of choice?
- skull xray
- MRI
- MRI
- worries about tumor so MRI
