Carotid Anatomy & Evaluation Flashcards
Where do the left and right carotid originate from?
Right: innominate/brachiocephalic
Left: second branch of aortic arch
Where do the carotid arteries terminate?
At carotid bifurcation, divide into ICA and ECA
What does the ICA communicate with in the brain?
Circle of Willis
What are the intracranial branches of the ICA?
1st: ophthalmic artery at carotid siphon (significant curve of distal ICA)
2nd: posterior communicating artery
After the ICA branches into the ophthalmic artery and the posterior communicating artery, what does it become?
Middle cerebral artery and anterior cerebral artery
What does the ICA supply?
Anterior brain- low resistance
Eyes (ophthalmic), forehead, nose (posterior communicating)
What are the 8 branches of the ECA?
- superior thyroid artery
- ascending pharyngeal artery
- lingual artery
- facial artery
- occipital artery
- posterior auricular artery
- superficial temporal artery
- maxillary artery
What does the ECA supply?
Face, neck, scalp- all high resistance
What arteries originate from the subclavian arteries?
vertebrals
What side is the vertebral artery larger on?
Left, directly off aortic arch
What happens to the vertebral arteries once they enter the skull at the foramen magnum?
Unite to form basilar artery
How long is the basilar artery?
3 cm
What does the basilar artery divide into? What does it supply?
Divides into posterior cerebral arteries which form part of circle of Willis, supply posterior cranial structures
What is the purpose of the Circle of Willis?
Provides collateral pathway that maintains flow to brain in case of stenosis or occlusion
Where is the Circle of Willis located?
Base of brain
What arteries make up the Circle of Willis?
Hexagonal arrangement of distal ICA, anterior cerebral & posterior cerebral arteries joined by anterior & posterior communicating arteries
When are communicating arteries used?
In cases of significant occlusion
How do the anterior cerebral arteries travel? What other vessel do they give rise to?
Travel medially toward midbrain (A1), give rise to anterior communicating artery (b/w 2 ACAs), then travel anteriorly
Where are the posterior cerebral arteries located? What do they supply?
Wrap around cerebral peduncle, supply posterior hemispheres
What artery is not technically part of the Circle of Willis?
middle cerebral artery
How does the MCA travel?
Laterally toward temporal bone with numerous branches
What percentage of ICA flow does the MCA carry?
75-80%
How does the size of the ACA compare to the MCA?
ACA < MCA
What is the most commonly seen collateral pathway?
ECA-ICA via orbital and ophthalmic arteries
What is a transient ischemic attack? How long do they last and what is the cause?
Fleeting neurologic dysfunction, symptoms < 24 hours, usually embolus from heart or carotid
What is RIND? How long does it last?
Reversible ischemic neurologic deficit, symptoms resolve but last over 24 hours, complete recovery
What is VBI? What are the symptoms?
Vertebral basilar insufficiency, bilateral symptoms: visual blurring, paresthesia, may have vertigo, ataxia, drop attacks (permanent)
What is CVA?
Cerebrovascular accident
Acute: sudden onset of symptoms
Stroke in evolution: symptoms come & go
Completed stroke: no progression or resolution
What are the causes of CVA?
Embolism, thrombosis, hemorrhage
What cerebrovascular problems cause transient vs permanent symptoms?
transient: TIA, RIND, VBI
permanent: CVA
Where do hemispheric symptoms arise from?
Anterior circulation
What is aphasia?
Inability to speak or express self, left hemisphere if right handed, opposite of dominant side
What is dysphasia?
Impairment of speech, lack of coordination, failure to arrange proper word order, left hemisphere
What is dysarthria?
Difficulty articulating speech due to muscle control and slurring, left or right hemisphere
What hemisphere is affected with lateralized paresthesia or lateralized weakness?
Contralateral hemisphere
What hemisphere is affected with hemiparesis?
Contralateral hemisphere
What is amaurosis fugax?
AKA transient monocular blindness, ipsilateral hemisphere or distal ICA
What hemisphere is affected when there is motor dysfunction?
Right or left contralateral hemisphere
What are symptoms of ICA lesions?
- unilateral paresis
- unilateral paresthesia
- aphasia
- amaurosis fugax
- less likely: myopia AKA nearsightedness, & homonymous hemianopia, defective vision in right or left halves of visual field
What are symptoms of MCA lesions?
- aphasia or dysphasia
- severe facial & arm hemiparesis
- behavioral changes
What are symptoms of ACA lesions?
- severe leg hemiparesis
- incontinence
- loss of coordination
What are symptoms of vertebrobasilar lesions?
- vertigo
- ataxia
- bilateral vision blurring or double vision
- bilateral paresthesia or anesthesia
- drop attacks: falling without loss of consciousness
What are symptoms of PCA lesion?
- dyslexia
- coma
- paralysis unlikely
What are symptoms of general posterior circulation disease?
- dizziness, fall
- syncope
- dysarthria
- severe headache
Where is palpation of the arteries commonly done?
Carotid, superficial temporal, subclavian and axillary
Where is auscultation usually performed? Bruit may not be heard in what percentage of stenoses?
At carotid or subclavian, not heard in >90% of cases
What happens if ICA is occluded?
- thrombosed intra & extracranially
- no sx
- ECA can act as collateral for distal ICA & communicate with vert to get blood to brain
If the ECA is acting as a collateral for the ICA, how are the waveforms affected?
ECA waveforms become low resistance
What happens if the CCA is occluded?
ICA may still have normal flow due to retrograde flow in ECA & other vessels supplying ICA
What happens if ECA occlusion occurs?
Not concerning due to numerous branches that act as collaterals
When is surgery performed on the vessels?
Not for occlusion due to collaterals, surgical intervention for high grade stenosis to relieve high velocities and prevent embolism
What is cerebral thrombosis and why does it happen?
Thrombus in brain-feeding artery that starves brain of oxygen, blood vessels with increased lipid deposits make blockage more likely
What is a cerebral embolism?
Thrombus forms elsewhere and travels through vessels, lodges in small vessels of brain, starving brain cells of oxygen
What increases risk of cerebral embolism?
Irregular heartbeat & hx of heart attack
What are 6 additional cerebrovascular conditions?
- atherosclerosis
- aneurysm
- dissection
- fibromuscular dysplasia
- carotid body tumor
- subclavian steal
What is fibromuscular dysplasia and who does it affect?
Condition that causes stenosis & aneurysms of vessels (bead appearance)
MC in young women and affects renal & carotid arteries
What is carotid body?
Small structure superior to bifurcation that regulates oxygen changes of blood & helps control heart rate by sensing pressure changes
What is carotid body tumor?
Highly vascular mass that develops between ICA & ECA, supplied by ECA, sx removed
What is subclavian steal?
- Subclav stenosis prox to origin of vert
- Subclav steals blood from vert to supply arm
What is the result of subclavian steal?
Vertebrobasilar insufficiency = neuro symptoms
What are the capabilities of a carotid exam?
- Localize area of blockage, lesion, stenosis
- Differentiate stenosis from occlusion
- Document progression of disease
- Identify surface characteristics
- Identify pulsatile mass ex. CBT, aneurysm
What are limitations for a carotid exams?
- dressings, skin staples, sutures
- size/contour of neck
- depth or course of vessels
- calc shadowing
- overestimation/underestimation of disease progression
What can cause overestimation of disease progression?
Accelerated flow due to
- cardiac output
- tortuous vessel
- compensatory flow
- incorrect doppler angle
What can cause underestimation of disease progression?
Accelerated flow not present due to
- missed acceleration flow jet
- long, smooth plaque formation
- stenosis at bulb
- incorrect doppler angle
What are 5 indications for a carotid exam?
- Cervical bruit
- F/u known carotid disease
- Evaluation of syncope, seizures, dizziness
- Evaluation of pt w/ hemispheric neuro symptoms
- suspected subclavian steal
What is plaque of retinal exam called?
Hollenhorst plaque
What spectral analysis technique is used during carotid evaluation?
Fast Fourier Transform: individual frequencies/velocities displayed with time on horizontal axis and various frequency shifts/velocities on vertical axis
How can we differentiate the ECA?
- feeds face
- smaller
- branches in neck
- bifurcates anteriorly
- high resistance
- temporal tap
How can we differentiate the ICA?
- feeds brain
- larger
- branches in head
- bifurcates posteriorly
- low resistance
- no response to temporal tap
What is the difference in smooth and irregular plaque?
smooth: continuous surface w/o irregularities
irregular: discontinuous surface that may contain ulcerations
What in intraplaque hemorrhage? What is ulceration?
IPH: anechoic area within plaque
ulceration: depression within plaque
What does spectral broadening represent?
Turbulence & loss of laminar flow, waveform is filled in
What do we want to document in a stenosis?
Max velocity through narrowest portion of lumen, distal to stenosis: disturbed flow patterns, turbulence, bidirectional flow
How can spectral waveform change distal to stenosis?
Can become continuous
What PSV/EDV correlates with what % of stenosis?
< 125 cm/s: normal or 1-15%
> 125 cm/s: 16-49%
> 125 cm/s PSV, < 140 cm/s EDV: 50-79%
> 125 cm/s PSV, > 140 cm/s EDV: 80-99%
Absent: Occluded
What can we see when dopplering an occluded vessel?
- CCA may have very low/absent ED flow
- Evidence of collateralization (ECA exhibiting high EDV)
- Absent ICA doppler or pre-occlusive thump
