Chapter 10: Intracranial Cerebrovascular Examination Flashcards
cessation of oxygenated blood circulation to the brain
cerebral circulatory arrest
endovascular mechanical thrombectomy used during ischemic stroke due to large vessel occlusion
cerebral thrombectomy
a change in cerebral blood flow in response to a vasoactive stimulus
cerebrovascular reactivity
A roughly circular anastamosis of arteries located at the base of the brain
circle of Willis
A vessel that maintains blood flow via a secondary route for a stenotic or occluded vessel
collateral
Microparticles circulating in the blood consisting of thrombi, platelet aggregates, or gas, which can be detected by Doppler ultrasound
emboli
Middle cerebral artery mean velocity divided by the submandibular internal carotid artery mean velocity. This ratio is useful in differentiating increased volume flow from decreased diameter when high velocities are encountered in the MCA or intracranial ICA
Lindegaard ratio
Expressed as the Gosling pulsatility index (peak systolic velocity minus end-diastolic velocity divided by the time-averaged peak velocity)
pulsatility
Disorders of hemoglobin, the molecule in red blood cells that delivers oxygen to cells, which distorts RBCs into a sickle shape
sickle cell disease
Ratio calculation used to determine vasospasm from hyperdynamic flow in the posterior circulation. The bilateral vertebral artery velocities taken at the atlas loop are added together and averaged. This averaged velocity is then divided into the highest basilar artery mean velocity.
Sviri ratio
A noninvasive test that uses ultrasound to measure the velocity of blood flow through the intracranial cerebral vessels
transcranial Doppler (TCD)
A noninvasive test of the intracranial cerebral blood vessels that uses ultrasound and provides both an image of the blood vessels and a graphical display of the velocities within the vessels
Transcranial Duplex Imaging (TCDI)
A sudden constriction in a blood vessel causing a restriction in blood flow
vasospasm
focal increase in velocity
poststenotic turbulence
use prestenotic/stenotic ratio
stenosis
absent flow on color imaging and Doppler
High-resistance signal proximal to occlusion
occlusion
MCA velocity >200 cm/s
Lindegaard ratio >6.0
can be present in more than one artery
temporal changes
severe vasospasm
brief signal lasting <300 ms
M-mode high-power tracks sloping in flow direction
amplitude at least 3 dB above background
unidirectional signal
signal has snap, chirp, or moan soand
emboli
absent, no flow signal
occluded with no residual flow
low systolic, only velocity signal
no antegrade residual flow
low velocity, damped systolic, and diastolic signal, with slow systolic acceleration, with a PI of <1.2
subtotal occlusion with sluggish antegrade flow
High PI >1.2, systolic dominant signal with >30% higher than contralateral MCA
stenotic with recanalization
velocity comparable to contralateral MCA with <30% difference and similar PI
Normal flow with total recanalization
abnormal velocity criteria for sickle cell anemia
> 200 cm/s
directly study the intracranial conducting arteries that lie at base of brain
TCD examinations
Diameter of basal cerebral arteries range from ____
2-4 mm
formed by the intracranial circulation of ICA; first becomes accessible by TCD exam in cavernous portion
anterior circulation (circle of Willis)
Three segments of carotid siphon
parasellar, genu, supraclinoid
ICA divides into:
middle cerebral artery
anterior cerebral artery
significant branches that arise from distal ICA
opthalmic artery (OA)
posterior communicating arteries (pCoAs)
courses medially from ICA for a short distance before passing forward as A2 or postcommunicating segment
ACA
Where are the two ACAs connected?
connected above optic chiasm by the anterior communicating artery (ACoA)
continuation of extracranial vertebral arteries once they pass through foramen magnum, enter subarachnoid space, and course beneath brainstem
intracranial posterior circulation
usually arise from distal part of vertebral; supply brainstem and cerebellum
posterior inferior cerebellar arteries (PICAs)
created by the joining together of the two VAs and ends by terminating into right and left posterior cerebral arteries (PCAs); gives rise to two paired set of branches, the anterior inferior cerebellar and superior cerebellar arteries
Basilar artery
initial short segment arising from BA; before connection to the PCoA is called the P1 or precommunicating segment
PCAs
require insonation through foramen magnum
VAs and BAs
What kind of TCD instrument is optimable?
1-2 MHz pulsed-wave transducer and spectral
M-mode capabilities
PSV, EDV, TAP-V, Gosling pulsatility index (PI)
uses simultaneous signal acquisition from 33 sample gates, placed at 2 mm intervals
Power M-mode (PMD)
Optimal transducer for standard duplex TCDI exam
broadband phased array sector transducer; 1-5 MHz frequency range
traces outer edge of spectral waveform; provides real-time calculations of quantitative values
envelope line
located over temporal bone, superior to zygomatic arch, and anterior and slightly superior to tragus of ear conch
transtemporal approach
relies on transmission of ultrasound beam through thin orbital plate of frontal bone, optic canal, and superior orbital fissure
transorbital approach
natural opening in skull through which spinal cord passes; transducer placed 1 1/4 inches below base of skull; sound beam aimed toward nasion
foramen magnum approach
retromandibular ICA signal; transducer placed at angle of jaw with beam directed cephalad
submandibular approach
used to calculate BA/VA ratio; transducer placed 1.25 inches below mastoid process and behind sternocleidomastoid muscle
atlas loop approach
provides physiological information that complements anatomic imaging studies
standard transcranial Doppler exam
5 primary criteria used for ID of each vessel segment
- approach
- sample volume depth
- direction of blood flow relative to ultrasound transducer
- the spatial relationship of one artery to another
- flow velocity
Flow velocity
MCA > ACA > PCA = BA = VA
arteries identified in the orbital approach
OA
carotid siphon
waveform of OA
low velocity
low diastolic flow
arteries identified in the temporal approach
MCA, ACA, terminal internal carotid artery (TICA), PCA
arteries identified in the foramen magnum approach
VAs and BAs
curves below brainstem and courses forward and superiorly; relatively long 33 +- 6mm
Basilar artery
Mechanical index is not to exceed ___ in an orbital approach
0.23
two hyperechoic lines shaped into a V in the orbital approach
lateral and medial rectus muscles
Branches of OA
central retinal artery and vein
lacrimal artery
long and short posterior ciliary arteries
waveform of OA
low velocity with high resistance
Where is the carotid siphon located?
below lateral and medial rectus muscles
transducer just superior and parallel to zygomatic arch
temporal approach
bright thin line produced by reflection from double layer of dura in interhemispheric fissure at midline
falx cerebri
echolucent butterfly or heart-shaped structure
midbrain
slightly above and parallel to lesser wing of sphenoid bone
middle cerebral artery
large median opening penetrating occipital bone
foramen magnum
How long is the BA?
3-4 mm
because of high attenuation no signals will be obtained through temporal bone window; occurs uni or bilaterally
hyperostosis of temporal bone
primary diagnostic features of waveform
alteration in velocity
deviations from laminar flow
changes in pulsatility
changes in direction of flow
can be calculated using equation
(PSV-EDV)/TAP-V
resistance index
initial slope or time lapsed from systolic onset to PSV
systolic upstroke
calculated as MCA mean velocity divided by submandibular ICA mean velocity divided
Lindegaard ratio
used for determining vasospasm from hyperdynamic flow in posterior circulation; bilateral VI mean velocities taken at atlas loop added together and averaged, averaged velocity is then divided into highest BA mean velocity
Sviri ratio
presence of good LMCS in ischemic stroke
better outcomes
reduced infarct size
quicker recanalization
can extend into intracranial VAs and BAs; potentially impact flow through circle of Willis
subclavian steal
most common conditions that produce intrinsic narrowing of cerebral arteries
thromboembolic
atherosclerotic disease
uncommon noninflammatory conditions that produce intrinsic narrowing of cerebral arteries
dissection
fibromuscular dysplasia
radiation induced vasculopathy
Moyamoya disease
inflammatory and hematologic causes that produce intrinsic narrowing of cerebral arteries
temporal arteritis
meningitis
toxin-related vasculitis
SCD
4 known risk factors that increase risk of large artery artherosclerotic stenosis
hyperlipidemia
arterial hypertension
cigarette smoking
diabetes mellitus
Most common mechanism of posterior circulation stroke
embolism
most common cause of occlusion beyond circle of Willis
embolism
several types of cardiac disease lead to cerebral embolism
cardiac arrythmias
ischemic heart disease
valvular disease
dilated cardiomyopathies
atrial septal abnormalities
intracardiac tumors
measures residual flow around clot, in general, larger amount of residual flow predicts success of thrombolysis
thrombolysis in brain ischemia
one of most significant causes of delayed cerebral ischemia
development of cerebral vasospasm during first 2 week period following initial bleed
transient, delayed narrowing involving cerebral arteries following SAH
cerebral vasospasm
When does onset of arterial contraction?
3-4 days following initial bleed, peak narrowing 6-8 days, resolution 2-3 weeks following SAH
goals of TCD in setting of SAH
detect elevated blood velocities that indicate cerebral vasospasm
identify patients at risk for DCI
Most frequently monitored artery
MCA
referred to as high-intensity transient signals
microembolic signals
utilizes multiple sample gates to construct M-mode display simultaneously with a single gate spectogram
PMD
remnant of fetal circulation appearing as a slit-like tunnel between right and left atria of heart
PFO
allows for passage of blood from right to left cardiac chambers
RLS
Gold standard for identifying presence of RLS
TEE with agitated saline injections
During a successful valsalva maneuver, velocities ____ during abdominal muscle contraction and ______ when patient relaxes
increase
decrease
genetic disorder that mostly occurs in African, Hispanic, Middle Eastern, and Asian Indian lineage
sickle cell disease
impacts red blood cells; causes development of sickle shape and become rigid, causing vascular injury
sickle cell disease
Elevated blood flow velocities in SCD related to:
severe anemia
vessel stenosis
vasodilation caused by tissue hypoxia
What is the range of the average diameter of basal cerbral arteries?
2-4 mm
It is estimated that 18% to 54% of individuals display variations at the level of the circle of Willis. Which of the following is NOT one of those variations?
a. variation in number of arteries
b. variation of caliber of vessels
c. variation of the course of vessels
d. variation of the origin of branches
a
Which statement about the anterior cerebral arteries is FALSE?
a. Both arteries (right and left) are frequently identical
b. The anterior communicating artery is located above the optic chiasm
c. Both arteries communicate via the anterior communicating artery
d. Both arteries first course medially to the internal carotid arteries
a
What is the term used when the posterior cerebral arteries depend on the internal carotid artery for blood flow (at least partly)?
fetal origin of the PCA
What is the optimal patient position for evaluation of the vertebral and basilar arteries through the foramen magnum?
lateral decubitus with head tilted inferiorly
Which of the following is a typical characteristic of a nonimaging transducer for transcranial Doppler?
a. 1 to 2 MHz pulsed wave
b. 1 to 2 MHz continuous wave
c. >4 MHz pulsed wave
d. >4 MHz continuous wave
a
What is the Doppler frequency range in standard duplex imaging system for transcranial imaging?
2-3 MHz
What is the initial target vessel to be explored through the transtemporal acoustic window?
MCA
What do the Lindegaard and the BA/VA ratios help categorize?
vasospasm
What does the relation MCA >ACA >PCA =BA = VA?
relative flow velocities
Which of the following is NOT a criterion used for the identification of vessels or vessel segments in the intracranial circulation?
a. the direction of flow in relation to the transducer
b. the diameter of the vessel
c. the sample volume depth
d. the vessel flow velocity
b
Which imaging technique creates a display that demonstrates flow intensity and dissection in bands of color at multiple depths, creating a “road map” to follow signals from vessels?
power M-mode
Which of the following is NOT a primary diagnostic feature of the Doppler signals for evaluation of intracranial vessels?
a. changes in vessel diameters from established criteria
b. changes in velocity from esetablished criteria
c. changes in flow pulsatility from established standards
d. changes in flow direction from established standards
a
Which of the following would cause anterior to posterior collateralization?
A. MCA occlusion
B. ACA stenosis
C. Mid basilar artery occlusion
D. Proximal vertebral artery stenosis
C
Which characteristic is not part of the five primary criteria used to identify intracranial arterial segment?
A. Flow direction
B. Pulsatility index
C. Sample volume depth
D. Window/approach used
B
A limited transcranial Doppler or transcranial duplex imaging exam could be ordered for all of the following except:
A. Evaluate for sickle cell anemia
B. Monitor microembolism during endarterectomy
C. Follow up for vasospasm
D. Evaluate single vessel patency
A
Which statement regarding the use (and advantages) of audio signals during TCD and TCDI is false?
A. Nuances in signal can be heard before they can be seen on the Doppler spectrum
B. High-velocity signals could be missed by turbulent flow on the Doppler spectrum
C. Audio signals can help in redirecting the sonographer in the acquisition of Doppler spectrum
D. TCDI does not have audio capability
D
Which of the following is the atlas loop approach used for?
A. Visualizing the internal carotid siphon
B. Visualizing the distal vertebral arteries
C. Obtaining data to characterize basilar artery vasospasm
D. Alternative window to the forsaken magnum approach
C
To ensure patient safety when using the transorbital approach, which technical setting should you always address?
A. Decrease the acoustic intensity
B. Increase the color Doppler scale
C. Decrease the velocity scale
D. Increase the Dopple gain
A
At a depth of approximately 65 mm from the trans temporal window, with a Doppler sample gate of 5 to 10 mm, you should obtain two Doppler spectra (one on each side of the baseline). What do these Doppler spectra correspond to?
MCA/ACA
When is evidence of vasospasm usually seen following subarachnoid hemorrhaging?
3-4 days after the bleed started
A 68 year old male patient presents to the vascular lab for TCD evaluation. During the exam, mean velocities in the MCA reach 140 cm/s proximal my, with turbulence and damped, delayed spectral waveforms noted distally. What do these findings suggest?
> 70% MCA stenosis
What is a remnant of the fetal circulation that appears as a slit-like tunnel between the right and left atria of the heart?
Patent foreman ovale
What is the most likely mechanism of cryogenic stroke in patients with a PFO and right-to-left cardiac shunt?
Paradoximal embolism
When performing TCD on a patient with sickle cell disease, velocities in the MCA are considered abnormal when they reach which value?
> 200 cm/s
On average, the center of the circle of Willis is approximately the size of a ______.
Thumbnail
The anterior intracranial arterial circulation is formed as a continuation of the _____.
ICA
The parasellar, genu, and supraclinoid segments are part of the _____.
Siphon
The anterior inferior cerebellar and superior cerebellar arteries are branches of the _____.
Basilar
From the trans orbital window, the carotid siphon is identified at a depth of _____ mm.
60-75
The best acoustic window to insinuate the vertebral and basilar arteries is through the ______.
Foramen of magnum
The vessel identified through the trans temporal window at a depth of 65 mm with posterior and inferior rotation on the transducer is the _____.
PCA
Independently of the technique used (TCD or TCDI), the documentation of data obtained on intracranial arteries is based on ____.
TAP
All the arteries examined during a TCD or TCDI examination supply the brain except the ______.
Opthamalic arteries
When the transducer is placed 1.25 in below the mastoid process and posterior to the steenocleidomastoid muscle, the technique is called the ______.
Atlas loop
The Gosling index expresses the _______ of the Doppler signal.
Pulsatility
The MCA mean velocity divided by the submandibular ICA mean velocity represents the calculation for the ______ ratio.
Lindegaard
Ipsilateral increased velocities observed in the ACA and PCA with a significant stenosis or occlusion of the MCA is a result of ______ collateralization.
Leptomeningeal
Evaluation of the MCA from a temporal window with a more posterior location will require aiming the transducer _____.
Anterior
The most common mechanism of posterior circulation stroke, usually of cardiac origin, is ___.
Embolism
Pediatric patients with _______ are recommended to have annual TCD screening to help prevent stroke.
Sickle cell anemia
For acute thrombosis, the _____ scale is used to classify changes that can occur rapidly with recanalization and reocclusion in acute stroke.
TIBI
Mean flow velocities in the MCA of >200 cm/s, a rapid daily rise in flow velocities and a hemispheric ratio of >6.0 predicts the presence of significant ______.
Vasospasm
A TCD signal that contains a very short or brief, high amplitude, unidirectional “snaps”, “chirps”, or “moans” indicates _______.
Microembolic signals
Which of the following is not a segment of the carotid siphon?
A. Auricular
B. Parasellar
C. Supraclinoid
D. Genu
A
Terminal branches of the internal carotid artery include:
The middle cerebral and anterior cerebral arteries
No imaging TCD equipment typically uses:
A 1-2 MHz pulsed wave transducer
Which type of duplex ultrasound transducer is used for TCDI examination?
A phased array with Doppler frequencies of 2-3 MHz
During a TCD examination, which of the following arteries do not normally display high flow during diastole?
A. MCA
B. PCA
C. BA
D. OA
D
Which of the following is not an acoustic window used during a TCD or TCDI exams.
A. Suboccipital
B. Transparietal
C. Transorbital
D. Submandibular
B
Which one of the following is not a subdivision of the temporal window?
A. Inferior
B. Anterior
C. Frontal
D. Posterior
A
Which statement below best describes the proper orientation for the foramen magnum approach?
A. The transducer is placed 2-3 inches below the base of the skull and the sound beam is aimed toward the nasion
B. The transducer is placed 2-3 inches below the base of the skull and the sound beam is aimed toward the parietal bone
C. The transducer is placed 1.25 inches below the base of the skull and the sound beam is aimed toward the parietal bone
D. The transducer is placed 1.25 inches below the base of the skull and the sound beam is aimed toward the nasion
D
During a TCD exam, primary criteria used for vessel identification include all of the following except:
A. Direction of flow relative to the transducer
B. Acceleration time
C. Mean flow velocity
D. Sample volume depth
B
Which statement correctly describes the ACoA and PCoA?
A. The ACoA is rarely identified, but the PCOA is normally seen inferior and posterior to the MCA
B. The ACoA and PCoA are virtually never identified during a TCD or TCDI exam
C. The PCoA is rarely identified, but the ACoA is normally easily seen connected to the right and left anterior cerebral arteries
D. The ACoA and PCoA are usually only identified when serving as collaterals
D
Using a trans temporal window, what initial depth should be used to obtain Doppler signals from the MCA?
50 mm
When performing a TCDI exam using the transoribital approach, the structure can be seen casting an acoustic shadow.
The optic nerve
The Lindegaard ratio is calculated by:
Dividing the MCA mean velocity by the submandibular ICA mean velocity
This calculated hemodynamic parameter is used to determine vasospasm from hyper dynamic flow in the posterior circulation.
The sviri ratio
Evidence of crossover collateral flow through the ACA can be found in the following except:
A. Retrograde flow in the A2 ACA segment Ipsilateral to the extracranial carotid stenosis
B. High velocities detected at midline in the small anterior communicating artery
C. Increas flow velocities in the contralateral ACA
D. Retrograde flow in the ACA, A1 segment Ipsilateral to the extracranial carotid stenosis
A
All of the following can be a cause of intracranial stenosis or occlusion except:
A. Meningitis
B. Temporal arteritis
C. Sickle cell disease
D. Buerger disease
D
Which of the following statements best describes changes following subarachnoid hemorrhage?
A. Vasospasm occurs within 24 hours following the initial bleed, peaks within 3-4 days, and resolves within 1 week
B. Vasospasm occurs approximately 7-10 days following initial bleed, peaks within 48 hours after onset of vasospasm, and resolves within the following week
C. Vasospasm beings 3-4 days following the initial bleed, peaks at 6-8 days, and resolves in 2-4 weeks
D. Vasospasm can occur at any time during the first 2 weeks following the initial bleed and resolves by week three
C
Microembolic signals have which of the following characteristics?
A. They should last less than 100 ms and have a signal at least 10 db kabobs background signals
B. They should last longer than 500 ms and have a signal at least 10 Db above background noise
C. They should last less than 300 ms and have a signal at least 3 dB above background signals
D. They should last longer than 300 ms and have a signal at least 3 dB above background signals
C
The use of TCD to detect patent foramen ovale involves the use of:
Agitated saline and the detection of Microembolic signals
Which statement best describes the utilization of TCD with theombolytic agents?
A. Ultrasound energy is used to activate thrombolytic agents
B. Ultrasound energy is used to burst microbubbles and release the thrombolytic agents
C. Ultrasound is strictly used to monitor blood velocities before and after administration of thrombolytic agents
D. Ultrasound energy can slightly move fibrin strands to allow for more contact with thrombolytic agents
D
3 segments of carotid siphon
Parasellar
Genu
Supraclinoid
Internal carotid artery branches
Ophthalmic artery
Posterior communicating artery
Anterior circulation
Cavernous internal carotid artery
Middle cerebral artery
Anterior cerebral artery
Anterior communicating artery
Posterior circulation
Middle cerebral artery
Anterior cerebral artery
Anterior communicating artery
Vertebral arteries
Basilar artery
Posterior cerebral arteries
What position should a patient be positioned for evaluation of posterior circulation?
LLD
Dedicated nonimaging TCD instrument
1-2 MHz pulled wave transducer
Dedicated duplex ultrasound system instrument
Broadband phased array
2-3 MHz Doppler frequency
4 MHz imaging frequencies
All vessels in a TCD study except _____, have low resistance with relatively high diastolic flow.
OA
For common acoustic windows used to assess cerebral vasculature
Transtemporal
Transorbital
Transoccipital
Submandibular
Located over the temporal bone, superior to zygomatic arch
Transtemporal
Transtemporal subdivided into
Posterior
Middle
Anterior
Frontal
Ultrasound is transmitted through the thin orbital plane of frontal bone
Transorbital approach
Transducer is placed at base of skull and aimed toward nasion
Foramen magnum approach
Transducer is placed at the angle of the jaw and beam is directed cephalad
Submandibular approach
Transducer is placed below the mastoid process, behind the sternocleidomastoid muscle
Atlas loop approach
Allows interrogation of the very distal extracranial ICA
Submandibular approach
Used to evaluate extracranial vertebral artery
Atlas loop approach
Five primary criteria used to identify vessels
Approach
Sample volume depth
Direction of blood flow relative to ultrasound transducer
Spatial relationship of one artery to another
Flow velocity
Arteries identified orbital approach
OA
Carotid siphon
Arteries identified temporal approach
MCA
ACA
TICA
PCA
Arteries identified foramen magnum approach
Vertebral arteries
Basilar arteries
Waveform opthalmis artety
Low velocity high resistance
Anatomic variations in circle of Willis
Differences in origin, size, course of vessel
Most common cause of intracranial stenosis
Atherosclerosis
_____ was the most common cause of occlusion beyond the circle of Willis
Embolism
The transient and delayed narrowing of basal cerebral arteries following subarachnoid hemorrhage
Vasospasm
Usually begins within 3-4 days after SAH, peaks around 6-8 days, and resolves within 2-4 weeks.
Vasospasm
Most commonly monitored artery with vasospasm
MCA
Short systolic spike followed by either a small retrograde deflection in diastole or no flow in diastole
Cerebral circulatory arrest
_____ patients are prone to stroke involving MCA and ACA
Sickle cell
