Cerebrovascular Flashcards
What are some examples of cerebroscular risk factors?
- Hypertension
- Diabetes
- Smoking
- Obesity/ diet
- Dyslipidemia
- Hypercholesterolemia
- Sex
- Age
- Patent foramen ovale
- Physical inactivity
- Genetic predisposition/ family history
- Homocystinaemia
- Cardiac disease
- Previous TIA or stroke
Why do we do a carotid auscultation for Bruitis?
It indicates abnormal flow if present
When doing a carotid auscultation for bruitis, turbulent blood flow does what?
Vibrate the vessel wall and creates a bruit
A bruit may not be detected in the case of what?
A severe stenosis due to significant diminished flow.
What is a thrill?
A palpable bruit
What are bilateral blood pressures?
Difference of >20 mmHg between sides which indicates a possible subclavian steal
What are signs and symptoms of anterior circulation steals?
- Behavioural abnormalities
- Hemiparesis/ hemiplegia
- Parenthesis
- Homologous hemianopia
- Amourosis fugax
What is anterior circulation?
Internal carotid artery - ICA
What is Hemiparesis/ hemiplegia?
Weakened or complete loss of function to one limb or side of the body
What is paresthesia?
Tingling, numb or burning sensation
What is homologous hemianopia?
Blindness or visual defect in half of the field of vision
What is amourosis fugax?
Partial or complete loss of vision
What is signs and symptoms of posterior circulation? (Vertebrobasilar artery)
- Ataxia
- Bilateral visual blurring
- Diplopia
- Drop attacks
- Dysphasia
- Motor/ sensory disturbances
- Vertigo
What is ataxia?
Lack of muscle coordination, can affect walking
1. Walking
2. Swelling
3. Eye movement
4. Speech
What is diplopia?
Double vision
What is drop attacks?
Sudden fall while walking or standing that is recovered from quickly
What is dysphasia?
Difficulty swallowing
What are motor/ sensory disturbances?
Unilateral, bilateral, or alternating
What are signs and symptoms of subclavian steals?
- Supraclavicular bruit
- Arm weakness
- Decreased arm pulses
- Arm pressures that are discrepancy by more than 20 mmHg
- usually the patient is asymptomatic with this condition therefore no treatment is undertaken
What is signs and symptoms of non localizing steals?
- Dizziness
- Syncope
- Dysarthria
- Headache
- Confusion
What is syncope?
Transient loss of consciousness
What is dysarthria?
Abnormal speech or difficulty with speech
What is arteriosclerosis?
Hardening of the arteries
What is arteriosclerosis directly related to? What does it result in?
Related to age resulting in degenerative change of the arteries that include loss of elasticity and thickening of the Intima over time
What is atherosclerosis?
Both hard and soft plaque within the arteries beyond the intimacy thickening of arteriosclerosis
What is the most common arterial disease?
Arteriosclerosis
Atherosclerotic plaque builds in what? And limits what?
Plaque builds in the arterial wall and limits or stops the blood flow by either narrowing the lumen (stenosis) or blocking the artery (occlusion)
What is a hemodynamically significant lesion?
A stenosis or an occlusion resulting in decreased blood pressure or flow distal to the obstruction, usually >50% diameter reduction
The vessel diameter typically needs to be reduced by at least how much to see a significant increase in PSV?
50%
What does the development of atherosclerosis start with?
Injury’s to the endothelial lining of the vessel wall
During the development of atherosclerosis injury could be due to what? (Stage 1)
A wide range of causes including certain risk factors, vasculitis or any hemodynamic stress
During the development of Atherosclerosis, injury exposes areas of the intimacy layer allowing what to happen? Stage 2
Lipids from the blood to enter, this is the inflammatory response, leading to the fatty streak
What happens during stage 3 of the development of atherosclerosis?
Platelets are deposited at the site and the muscle cells respond by becoming consumed with fat
During stage three of atherosclerosis development, the bodies attempt to repair injury results in what?
The formation of scar tissue (fibrosis), leaving a tough fibrous cap overlying the soft fatty portion of the plaque
What happens during stage four of the development of atherosclerosis?
- Fibrous cap can be disturbed by hemorrhage calcification and thinning lead to further disruption of the endothelial layer, resulting in ulcerative plaque. This type of plaque is unstable and can be release emboli or thrombus into the bloodstream
During stage four of the development of atherosclerosis there is hemorrhaging from what?
The vasa vasorum into the plaque causing ischemia learning to the breakdown of the fibrous cap and endothelium
What does this image demostrate?
Stage 1 of the development of atherosclerosis
What does this image demonstrate?
Stage two of the development of atherosclerosis
What does this image demonstrate?
Stage 3 of the development of atherosclerosis
thickening- plaque formation
What does this image demonstrate?
Stage 4 of atherosclerosis
late changes
What does the echogenicity of plaque morphology determined by?
Determined by the compositions of
1. Lipids
2. Collagen
3. Hemorrhage
4. Calcification within the plaque
What does anechoic mean for plaque?
No echogenicity, contains lipids and/ or intraplaque hemorrhage
What does hypoechoic mean for plaque?
Low echogenicity, fibrofatty plaque
What does hyperechoic mean for plaque?
Moderate echogenicity (fibrous plaque), shadowing may or may not be present
What does calcific mean for plaque?
Highly reflective plaque with shadowing
What does this image demonstrate?
Mixed echogenicity with hypoechoic regions
What does this image demonstrate?
Dominantly echolucent with small areas of echogenicity
What does this image demonstrate?
Dominant echogenic with small areas of echogenicity
What does this image demonstrate?
Calcified plaque
What does this image demonstrate?
Intraplaque hemorrhage
What does intraplaque hemorrhage present like?
Hypoechoic regions with thin fibrous cap, “Eggshell” pattern
What does this image demonstrate?
Ulceration
In terms of plaque formation and morphology, what is composition determined by?
The levels of lipid, collagen, hemorrhage and calcification
What does fibrofatty plaque contain and what does it look like sonographically?
Contains lipid material, low echogenicity, acoustics are similar to blood with a uniform echo distribution
What does fibrous plaque look like? What forms this?
Moderate to strong echogenicity, lipid or thrombus may create hypoechoic regions
What is complex plaque?
Multiple levels of echogenicity, acoustic calcific shadowing may or may not be present
In terms of plaque formation and morphology textures can be what?
Homogenous or heterogenous
In terms of plaque formation and morphology, what is surface?
Either smooth or irregular
What is a partial obstruction?
- Intima bulges as the plaque grows gradually narrowing the lumen,
- Leads to ischemia in the area being supplied
What is a complete obstruction?
Occlusion will cause infarction and necrosis of the area being supplied
What is a thrombosis?
Blood clot formed over the plaque which further decreases the lumen and contributes to ischemia or infarction
What is emboli?
- Thrombus that has broken off and become embolus
- Travels to areas downstream that are too narrow for it to pass causing ischemia and infarction
What is an aneurysm?
When plaque weaken the vessel wall and can cause a bulge to develop
Where is it rare to have aneurysms?
Cervical carotid arteries
What are vessel calcifications?
- Calcium salts from the blood may be deposited
- Results in hardening of the vessel walls making them brittle and prone to rupture
What is a asymptomatic neurologic defect?
When no cerebral and retinal symptoms of vascular disease
What is the most common indication for asymptomatic patients?
Auscultations of a bruit
What is a transient ischemic attack (TIA)?
Brief episode of neurological symptoms in which cell death does not occur
How long does transient ischemic attacks last?
1-30 minutes
In terms of transient ischemic attacks, neurologic deficit lasting less than 24 hours and consistent with ischemia is considered what TIA. T/F?
True
What is considered resolving/ Reversing/ ischemic neurological deficit (RIND)?
- Neurological event with symptoms lasting longer than 24 hours to within 3 weeks
- No permanent neurological damage
What is a cerebrovascular accident?
Results from a loss of blood supply that has left some permanent brain damage and subsequent loss of motor, sensory or cerebral function
What might SVA/ Stroke be further classified as?
- Acute- sudden onset
- Usable in evolution, symptoms come and go
- Completed, no progression or resolution, stable
What does vertebrobasilar insufficiency (VBI) cause?
Causes bilateral symptoms of
1. visual blurring
2. vertigo
3. Ataxia
4. Drop attacks
What are Norma carotid velocities
Non-hemodynamically significant stenosis <50% diameter
In terms of normal carotid velocities what are the doppler waveforms and flow velocities?
- Low resistance in the CCA, ICA and vertebral artery
- High resistance in the ECA
- PSV should be similar throughout the CCA
- Younger people will have higher velocities
In terms of Anterior circulation, EDV is above the baseline except when?
- CCA or ECA may have a short period of revered flow at end systole
- Flow reversal can be seen in the bulb
- If aortic regurgitation is present a longer period of reversed flow will be observed in the CCAs bilaterally
What is a stenosis or stenotic zone?
Narrowed portion of a vessel usually caused by plaque deposits but can be due to extrinsic compressions
What is a critical stenosis?
Reduces both flow and pressure. This is equivalent to a 50% diameter reduction/ 75% area reduction
Tandem stenoses have a what comparative effect on a single lesion?
These have a greater hemodynamic effect than a single lesion due to energy losses that occur at the entrances and exits of the stenotic segments
Most carotid stenosis occur in the first 1-2 cm (origin) of the what?
ICA
What are some factors affecting stenosis velocity?
- Length and diameter of the narrowed segment
- Endothelia surface roughness
- Edge irregularity of narrowing
- Flow rate
- Physiologic
- Collateral circulation presence
- Normal Vessel anatomy
In terms of carotid stenosis, Colour doppler can help determine what? What does spectral doppler do?
The location and extend of a stenosis, but spectral analysis is used for accurately assess the stenotic zone?
Colour doppler is limited by what?
Vessel tortuous its and Shadowing from calcific plaque
Positive ultrasound results may be correlated with what in terms of carotid stenosis?
Angiographic studies, especially if surgery is indicated. MRA is also a direct test
In terms of assess/performing a carotid stenosis exam what must we do?
- Compare both sides of the CCA for inflow/ outflow
- Categorize and image ICA disease by referring to (ICA/CCA ratios)
- Look at ECA for stenosis
- Assess vertebras for flow direction and possible obstruction
- Assess SCA for obstruction
- Other pathology
When looking for a carotid stenosis specifically peak systolic velocity, what must we look for?
- Search lumen for highest velocity
- Significant stenosis has a high pitched hissing sound
- >50-60% diameter reduction - Volume flow decreases rapidly
- > 70 diameter reduction - velocities start do decrease rapidly
- >80% reduction reduces PSV to below normal levels
What is the most important factor when looking for carotid stenosis?
Peak systolic velocity
When looking for end diastolic velocity for carotid stenosis, what should we look for?
- <50% diameter reduction the EDV remains within the normal range
- > 50% reduction causes an increase in diastolic velocity
- > 70% reduction sees a rapid rise in diastolic velocity
- valuable for detecting high- grade stenosis
What is the systolic velocity ratio?
PSV in ICA/ PSV in CCA
What factors affect systolic velocity ratio?
Physiologic factors such as hypertension
What would make the systolic velocity ratio invalid?
When the CCA or Bulb has a stenosis.
What happens when the systolic velocity ratio is invalid/ abnormal?
When the ratio is abnormal and all other parameters are normal such as velocities and no plaque it should be disregarded
What is trickle flow or pre- occlusive stenosis?
When the stenosis is so severe that the blood trickles through the residual lumen
In terms of trickle flow or pre-occlusive stenosis, When an occlusion is being considered one Must set system controls for low flow how?
- Low wall filter
- Low PRF
- Increased colour gain
- Increased sample size
- Power doppler may be very helpful in this situation
What does this image demonstrate?
Carotid stenosis
When is total occlusion present?
Total occlusion is present when no flow is detected by colour or spectral doppler with appropriate setting
When determining the extent of total occlusion what are some things we can look for/ see?
- Lumen filled with plaque, may be obscured by calcific plaque
- Colour flow or doppler signal should NOT be detracted with system controls set for low flow
- Arterial vessel pulsations are absent
- Isoechoic or slightly echogenic to surrounding tissue therefore making it difficult to visualize the vessel walls
In terms of occlusion specifically a long standing occlusion, what would the vessel size be?
Small vessel size
Nearly occluded vessels may have what kind of sign?
String sign
ICA to CCA occlusion has what ratio of predominance?
10-1
In terms of total occlusion, what is internalization of ECA?
When the ECA may have increased flow with a higher diastolic velocity than normal
In terms of total occlusion, the contralateral CCA may have what type of velocity?
A compensatory increased velocity
In terms of total occlusion, the ipsilateral CCA will have what kind of sound and show what?
- Thump sound
- Show a decreased PSV and an absent or reversed diastolic component
Bilateral diminished CCA velocities may indicate what?
Poor cardiac output
Unilateral diminished CCA velocity suggests what?
Ipsilateral Proximal disease
Spectral broadening increases with what?
An increase in severity of the stenosis
To confirm occlusions what must we do?
- Low flow settings, increased colour gains
- Increase sample volume size but avoid ECA branches and veins
- Interrogate distal to the bulb in transverse and sagittal with PW and colour doppler
Should we measure the velocity in transverse to confirm occlusions?
NO! The angle is not accurate
When confirming occlusions, with ICA occlusions diastolic flow may appear how?
Absent
When confirming occlusions, in 2D the ICA may appear how?
With plaque and motion and may be observed with each pulse
When confirming occlusions intracranial ICA occlusion will demonstrate what?
No end diastolic flow in the more distal portal of the ICA
What can we see with a pre-stenotic region (proximal) in terms of pulsatility?
- Increased pulsatility with severe stenosis
- Staccato waveforms
What do staccato waveforms look like?
- Sharp, narrow systolic peak
- Low systolic velocity
- Little diastolic flow
- Reversal in early diastole
- “Thump” sound heard