Cerebrovascular Flashcards
What are some risk factors for cerebrovascular pathophysiology? (14)
- Hypertension
- Diabetes
- Age
- Smoking
- Male
- Obesity
- Inactivity
- Cardiac disease
- Patent foramen ovale
- Previous TIA or stroke
- Dyslipidemia
- Hypercholesterolemia
- Genetics/Family history
- Homocystinaemia
If a bruit is found during carotid auscultation, what does this indicate?
Abnormal flow (turbulent)
How is a bruit formed?
Turbulent blood flow vibrates the vessel wall
What is a palpable bruit known as?
A thrill
Why may a bruit not be detected in the case of a severe stenosis?
Due to significantly diminished flow
If there is a difference of >20mmHg between sides, what could this indicate?
Possible subclavian steal
What is ataxia?
A lack of muscle coordination which can affect walking, swallowing, eye movement, speech etc.
What is diplopia?
Double vision
What are drop attacks?
A sudden fall while walking or standing that is recovered from quickly.
What is dysphagia?
Difficulty swallowing
What is Amaurosis fugax?
A complete or partial loss of vision
When someone has weakness or complete loss of function to one limb or one side of the body, what is this known as? (2)
Hemiparesis/Hemiplegia
When some experiences a tingling, numb, or burning sensation, what is this known as?
Paresthesia
What is aphasia/dysphasia?
Inability to speak or comprehend language
If someone has blindness or a visual defect in half of the field of vision, what is this known as?
Homonomous hemianopia
Visual disturbances are caused from what kind of symptoms?
Ipsilateral - Vision disturbances will occur on the same side as the side of the brain with a lack of blood supply.
Body disturbances are caused from what kind of symptoms?
Contralateral - Body disturbance will occur on the opposite side of the brain that has the lack of blood supply.
What is associated with irritation of the endothelial lining of the vessel?
Smoking
What are the signs and symptoms of the anterior circulation? (6)
- Behavioural abnormalities
- Amaurosis fugax
- Hemiparesis/hemiplegia
- Paresthesia
- Aphasia/dysphasia
- Homonomous hemianopia
What are the signs and symptoms of the posterior circulation? (8)
- Ataxia
- Bilateral vision blurring
- Diplopia
- Drop attacks
- Dysphagia
- Motor/sensory disturbances
- Vertigo
- Subclavian steal syndrome
What are signs of a subclavian steal? (3)
- Supraclavicular bruit
- Arm weakness
- Arm pressures that differ more than 20 mmHg
What are signs and symptoms that are non-localizing to anterior or posterior circulation? (5)
- Dizziness
- Syncope
- Dysarthria
- Headache
- Confusion
What is arteriosclerosis?
Condition of hardening of the arteries resulting in loss of elasticity and thickening of intima over time
What is arteriosclerosis directly related to?
Age
What is atherosclerosis?
A form of arteriosclerosis referring to the hard and soft build-up of plaque beyond the intimal thickening of arteriosclerosis
What is the most common arterial disease?
Atherosclerosis
Atherosclerotic plaque can narrow the lumen and is called a?
Stenosis
Atherosclerotic plaque can block the artery which is called what?
Occlusion
What diameter reduction is required in a vessel to notice hemodynamic changes (hemodynamically significant)?
> 50%
The CCA supplies the ICA with what percentage of blood?
70%
What type of resistance should be seen in a normal CCA, ICA, Vertebral and ECA?
CCA, ICA, Vert = low resistance
ECA = High resistance
In a normal carotid, the EDV us above the baseline except for when? (2)
- CCA or ECA may have short period of reversed flow at end systole
- Flow reversal in bulb
If aortic regurgitation is present, what should be visualized in the carotids?
Longer period of reversed flow in the CCAs bilaterally
A stenosis is usually caused by plaque deposits but can also be due to what?
Extrinsic compression
As flow goes through the stenotic zone, it must what?
Increase in velocity to maintain blood volume
Through a stenosis, what principle is used?
Bernoulli
High velocity/low pressure through stenosis and low velocity/high pressure distal to stenosis
A critical stenosis does what?
Reduces both flow and pressure
50% diameter reduction and 70% area reduction
What has a greater hemodynamic effect than a single lesion?
Tandem stenoses due to energy losses that occur at the entrances and exits of stenotic segments
Why does a tandem stenosis 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 stenoses occur where?
First 1-2 cm of the ICA
What are factors that affect stenosis velocity? (7)
- Length and diameter of the narrowed segment
- Endothelial roughness
- Edge irregularity of narrowing (abrupt/gradual)
- Flow rate
- BP/CO/peripheral resistance
- Collateral presence
- Vessel anatomy (Size)
What is the best method for accurately assessing the stenotic zone?
Spectral analysis
What is color Doppler of the carotid stenosis limited by?
Vessel tortuosity and acoustic shadowing from calcific plaque
What are we assessing the vertebrals for?
Flow direction and possible obstruction
What is the most important parameter on the spectral display?
Peak systolic velocity (critical to search lumen for the HIGHEST velocity).
What does a significant stenosis sound like?
High pitched hissing
What happens with a diameter reduction >50-60%?
Volume flow decreases rapidly
What happnes with a diameter reduction >70%?
Velocities decrease rapidly
With a diameter reduction >80% what happens to the PSV?
Reduces below normal levels
What happens to the EDV with <50% diameter reduction?
Remains within normal range
What happens to the EDV with >50% diameter reduction?
Increase in diastolic velocity
What happens to the EDV with >70% diameter reduction?
Rapid rise in diastolic velocity
What factors affect the systolic velocity ratio?
Physiologic factors
Ex.
Hypertensive = higher velocities
Diminished CO = lower velocities
What is the systolic velocity ratio (VR)?
Ratio = PSV in ICA / PSV in CCA
When can the systolic velocity ratio be used?
Only if there is a stenosis in the ICA
When is the VR invalid?
If the CCA or Bulb have a stenosis
How can a possible total occlusion be assessed for low/trickle flow? (5)
- Lower wall filter
- Lower PRF/scale
- Increase colour gain
- Increase sample size
- Use power doppler
With total occlusion, what is the sonographic appearance?
Vessel is isoechoic or slightly echogenic to surrounding tissue an no flow is detected with colour or spectral doppler
The string sign means that the vessel is?
Nearly occluded
Between the ICA and CCA, which is more likely to become occluded?
ICA 10:1
If the ICA is occluded, what may be seen in the ECA and what is this called?
Increased flow with high diastolic velocity than normal
Termed “internalization of the ECA”
Bilaterally diminished CCA velocities may indicate what?
Poor cardiac output
Unilaterally diminished CCA velocities may indicate what?
Ipsilateral proximal disease
What on the spectral display will increase with the severity of the stenosis?
Spectral broadening
A distal occlusion can be indicated by what kind of waveform?
Staccato
If there is an occlusion in the ICA, what may be seen in the CCA?
Absent diastolic flow
How does a waveform appear proximal to a severe stenosis and what is this termed?
- Increased pulsatility
- Sharp, narrow systolic peak
- Low systolic velocity
- Little diastolic flow
- Reversal in early diastole
“Staccato”
What is heard with a staccato waveform, indicating a severe distal stenosis?
Thump
A pre-stenotic waveform may look normal, what would give it away?
PSV would be very low
Immediately distal to the stenosis, flow spreads out resulting in what?
Turbulence
Where is maximum disturbance seen in a stenosis?
1 cm distal
At what point distal to a stenosis does turbulence diminish?
2 cm
At what point distal to a stenosis does laminar flow resume?
3 cm
Potential energy is higher or lower post stenosis?
Lower
What may the only clue to a severe stenosis be if the stenosis is obscured by calcific plaque?
Post-stenotic turbulence
What waveform will be seen distal to a severe stenosis (3 qualities) and what is this called (3 names)?
A dampened waveform
- PSV reduced
- Blunted systolic peak
- Diastolic flow increased
Called Tardus parvus/pulsus parvus/ pulsus tardus
A low to zero EDV may indicate what if seen in the CCA?
A Distal CCA, carotid bifurcation and/or prox ICA high grade stenosis or occlusion
What should be considered if a ≥30 cm/s difference between the right and left CCA velocities is observed at multiple levels? (4)
- Proximal obstruction
- Vessel tortuosity
- Tight distal CCA stenosis
- Compensatory flow due to a contralateral occlusion
What velocities would indicate a >50% stenosis in the ECA?
PSV >150-200cm/s with plaque and post-stenotic turbulence
In the presence of a severe ICA stenosis/occlusion, what will be seen in the ECA?
Low resistance flow pattern due to it acting as a collateral