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Vascular 3 > Module 3 : Intracranial Arteries > Flashcards

Module 3 : Intracranial Arteries Flashcards

1
Q

how is doppler ultrasound use to asses cerebral hemodynamics

A
  • measures blood flow velocities in the basal vessels in the circle of willis
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2
Q

what must be known before performing TCD

A
  • status of the extra cranial vessels
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3
Q

what type of pulse wave doppler is used with TCD

A
  • range gated [ulsed wave doppler
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4
Q

what is non imaging PW doppler with a spectral analyzer used for

A
  • excellent signal to noise ratio, lower bandwidth

- variable focusing depth, transmit power, adjustable gate depth

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5
Q

is TCD or TCI more portable

A
  • TCD
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6
Q

what is the most common pitfall of TCD

A
  • misidentification of vessels
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7
Q

what y parameters aid in the identification of vessels with TCD

A
  • depth of insonation
  • flow velocity
  • direction o fbeam angle
  • response to carotid compression
  • direction of flow
  • probe position
  • traceability of vessels
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8
Q

what is TCI (TCCD) imaging

A
  • adds imaging and uses color flow to act as a guide during the TCD exam
  • also allows placement of sample volume
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9
Q

what decreases doppler sensitivity with TCI

A
  • larger footprint
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10
Q

what type of doppler is preferred with TCI imaging

A
  • power doppler Duttons to increased sensitivity and angle independence
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11
Q

what is the most common application of TCD

A
  • serial monitoring of MCA and other vessels for vasospasm
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12
Q

what are 9 other applications of TCD/ TCI imaging

A
  • monitor vasospastic effect of sickle cell anemia
  • detect intracranial stenosis and occlusion
  • adjunct to extra cranial and carotid duplex stenosis
  • asses collateral circulation
  • functional reserve testing
  • evaluate intracranial aneurysm and AV malformation
  • confirm brain death
  • intraoperative monitoring
  • detect right to left cardiac shunts PFO
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13
Q

what are 5 limitations to TCD

A
  • recent eye surgery may eliminate trans orbital approach
  • no window or bone to thick
  • inaccurate identification of vessels with TCD
  • patient compliance
  • technical expertise
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14
Q

what are the 3 segments of the internal carotid artery

A
  • cervical ICA
  • Petrous ICA
  • cavernous ICA (carotid siphon)
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15
Q

where is the location of the cervical ICA

A
  • carotid bifurcation to the carotid canal of the petrous portion of the temporal bone
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16
Q

where is the location of the petrous ICA

A
  • runs through petrous portion of the temporal bone

- not visualized with ultrasound

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17
Q

what are the three portions of the cavernous ICA

A
  • parasellar portion (prox segment)
  • genu portion (bend)
  • supraclinoid portion (distal segment)
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18
Q

what is the first major branch of the ICA and what portion of the ICA does it arise from

A
  • ophthalmic artery

- cavernous portion of the ICA

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19
Q

what two vessel bifurcate from the terminal ICA

A
  • anterior cerebral artery

- middle cerebral artery

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20
Q

how many congenital malformations of the circle of willis are there

A
  • at least 9
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21
Q

what is the most common variations

A
  • involve the communicating arteries
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22
Q

what is the size of the circle and where is it located

A
  • 3cm

- base of the brain

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23
Q

are velocities in the circle of willis faster in the anterior or posterior circulation

A
  • anterior (ICA distribution)
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24
Q

which vessel carries the majority of the flow

A
  • MCA
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25
Q

rank the velocities in the vessels from highest to lowest

A

MCA»ACA»PCA»BA»VERTS

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26
Q

do velocities in the circle of willis increase or decrease with age

A
  • decrease
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27
Q

what percentage of population have an intact and functioning circle

A
  • 50%
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28
Q

what percentage of population have the classic circle configuration

A

18-25%

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29
Q

what is the course of the MCA

A
  • laterally towards the temporal bone with several branches
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30
Q

what are the 2 segments of the MCA and what are their locations

A
  • M1= form MCA origin to first branch

- M2= MCA distal to first branch

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31
Q

what is normal velocity range of MCA

A
  • <90

- usually 55 +/- 12

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32
Q

what are the 2 segments of the ACA and what are there course

A
  • A1 = course medially towards the midbrain

- A2 = course anteriorly to supply anterior segments of the brain

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33
Q

what vessel does the ACA give rise to

A
  • anterior communicating artery which runs between the two ACAs
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34
Q

what is the purpose of the posterior cerebral artery

A
  • perfuse posterior hemispheres

- wrap around cerebral peduncles

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35
Q

what are the 2 segments of the PCA and what are there course

A
  • P1 = origin to the posterior communicating artery

- P2 = distal to PCoA

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36
Q

which vessel arises from P1

A
  • posterior communicating artery
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37
Q

what is the purpose of PCoA

A
  • connects to the anterior circulation and is a route for collateralization
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38
Q

what vessel do the vertebral arteries arise from

A
  • subclavian arteries
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39
Q

what is the course of the vertebral arteries

A
  • course between the transverse processes of the spine

- enter the skull at the foramen magnum

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40
Q

what are the two intracranial branches of the vertebral artery

A
  • anterior spinal artery

- posterior inferior cerebellar artery

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41
Q

what is the basilar artery formed by

A
  • two intracranial vertebral arteries
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42
Q

how long is the basilar artery

A

3cm

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43
Q

what does the basilar artery bifurcate into

A

tow posterior cerebral arteries

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44
Q

what vessels allow for cross filling and collateralization when an ICA obstruction is present

A
  • ACoA

- PCoA

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45
Q

what happens in patients with a nonfunctioning circle if an ICA obstruction occurs

A
  • more significant neurologic ischemia
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46
Q

what are the four different approaches or windows to allow insonation of the arteries and what is the assumed angle of insonation

A
  • transtemporal
  • transorbital
  • transforamenal/suboccipital
  • submandibular (uncommon)
  • 0º
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47
Q

What is the TCI imaging method

A
  • noninvasive imaging of the intracranial arteries with color
  • determines whether there is flow in the vessel
  • real time
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48
Q

how is vessel identification done with TCD

A
  • probe portion and beam angle
  • depth of vessel
  • flow direction
  • traceability of vessel
  • mean velocity value
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49
Q

what are the two different mean velocities with TCI imaging

A
  • time averaged mean velocity

- time averaged peak velocity

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50
Q

what is the time averaged mean velocity

A
  • used for flow volume calculation

- when the mean velocity calculation is displayed they’ll be a line running through the middle of the waveforms

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51
Q

what is the time averaged peak velocity

A
  • used in TCD and TCI
  • not refereed to as mean velocity, MEAN OF THE PEAK VELOCITY OVER TIME
  • all TCD velocity values are mean velocities
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52
Q

what does “mean” mean

A
  • mean of the peak velocities over time referred to as TAMX
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53
Q

what is the most promising TCD/TCI window

A
  • transtemporal
54
Q

what vessels are being interrogated when an anterior angulation of 6º is used from the trans temporal window

A
  • MCA, portion of carotid siphon, ACA, ACoA
55
Q

what vessels are being interrogated when an posterior angulation of 5º is used from the trans temporal window

A
  • PCA, basilar artery, PCoA
56
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the MCA

A
  • 30-60mm
  • antegrade flow
  • 55cm/sec
57
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the MCA/ACA bifurcation

A
  • 55-65mm
  • bidirectional flow
  • 50cm/sec
58
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the ACA

A
  • 60-80mm
  • retrograde flow
  • 50cm/sec
59
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the ACoA

A
  • 70mm

- flow direction is present dependant on collateralization

60
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the PCA P1

A
  • 60-70mm
  • antegrade flow
  • 40cm/sec
61
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the PCA P2

A
  • 65-70mm
  • retrograde flow
  • 40cm/sec
62
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the PCoA

A
  • only if fiction

- not routinely assessed

63
Q

what is the insonation depth, flow direction, and velocity from the transtemporal window in the TICA

A
  • 55-65mm
  • antegrade flow
  • 39cm/sec
64
Q

what are the 3 potential locations of the transtemporal windows

A
  • posterior
  • middle
  • anterior
65
Q

where is the probe placed for the trans orbital window

A
  • probe situated medially on closed eyelid
66
Q

what is the insonation depth, flow direction, and velocity from the transorbital window in the ophthalmic artery

A
  • 40-60mm
  • antegrade flow
  • 21cm/sec
67
Q

what is the insonation depth, flow direction, and velocity from the transorbital window in the 3 segments of the carotid siphon

A
  • depths 60-80mm
  • paraseller = antegrade, genu=bidirectional, supraclinoid= retrograde
  • 47cm/sec
68
Q

what technical parameter must be adjusted when scanning through the transorbital window

A
  • power should be reduced to prevent damage to the eye and scanning time should be limited
69
Q

what is the probe placement for the transforamenal window

A
  • midline approach, angulation right to left
70
Q

what is the insonation depth, flow direction, and velocity from the transforamenal window in the vertebral window

A
  • 60-90mm
  • retrograde flow
  • 38cm/sec
71
Q

what is the insonation depth, flow direction, and velocity from the transforamenal window in the basilar artery

A
  • depth >80mm
  • retrograde flow
  • 40cm/sec
72
Q

what vessels are interrogated from the submandibular window

A
  • extradural segments of the distal ICA and carotid siphon
73
Q

what is the insonation depth, flow direction, and velocity from the submandibular window in the extradural segments of the distal ICA and carotid siphon

A
  • 80mm
  • retrograde flow
  • 30cm/sec
74
Q

what do the vessels do with the collateral pathway through the ACoA on the normal side

A 
MCA= toward, normal
ACA = away elevated
PCA P1 = toward, normal 
PCA P2 = away, normal 
BA = away normal
75
Q

what do the vessels do with the collateral pathway through the ACoA on the diseased side

A 
MCA = towards, normal/increased
ACA = toward, turbulent
PCA P1 = towards, normal 
PCA P2 = away, normal 
BA = Away normal
76
Q

what do the vessels do with the collateral pathway through the PCoA on the normal side

A 
MCA = toward normal
ACA = away elevated 
PCA P1 = toward normal 
PCA P2 = away normal 
BA = away, elevated also expect elevated VA's
77
Q

what do the vessels do with the collateral pathway through the PCoA on the diseased side

A 
MCA= toward, normal/increased
ACA=toward turbulent
PCA P1 = toward elevated
PCA P2 = away normal 
BA = away, normal
78
Q

what do the vessels do with the collateral pathway through the OA on the normal side

A 
MCA = toward normal 
ACA = way normal 
PCA P1= toward normal 
PCA P2 = away normal 
BA = away normal
79
Q

what do the vessels do with the collateral pathway through the PCoA on the diseased side

A

MCA = toward, velocity dependant on capability of OA flow
ACA = toward, velocity dependent on capability of OA flow
PCA P1 = toward normal
PCA P2 = away, normal
BA = away, normal

80
Q

what are the 11 clinical applications of transcranial doppler

A
  • intracerebral aneursym
  • intracranial stenosis/occlusion
  • extra cranial stenosis/occlusion
  • AV malformation
  • intraoperative monitoring
  • vasospasm
  • brain death
  • functional reserve testing or vasomotor reactivity
  • screening patients with sickle cell anemia
  • emboli detection
  • ## PFO
81
Q

what does aneurysmal disease result from

A
  • wakening fo the structural proteins within the media
82
Q

what can large aneurysms have a risk of

A
  • constricting surrounding arterial flow
  • rupture
  • subsequent subarachnoid hemorrhage
  • cerebral infarct
83
Q

what is the most common site for intracranial aneurysm

A
  • ACoA

- especially when associated with SAH

84
Q

what are two other common sites of intracranial aneurysms

A
  • PCoA

- MCA bifurcation

85
Q

what will stenosis look like in transcranial doppler

A
  • large basal arteries show increased velocity, disturbed flow with increased spectral broadening and co-vibration phenomenon
86
Q

what are the pitfalls of evaluating for stenosis intracranially

A
  • changes can be due to collateral flow or vessels supplying AVM’s
87
Q

what will occlusion look like in transcranial doppler

A
  • absence of arterial signal at expected depth, patent communicators, and altered flow in communicating vessels
88
Q

what are the pitfalls of evaluating for occlusion intracranially

A
  • inadequate temporal window causing non visualization, displacement of vessel form its normal position by a tumor
89
Q

how is patency of the circle of willis performed

A
  • tested with compression or oscillation maneuvers
90
Q

how is compression used to asses circle of willis

A
  • application go slow pressure to CCA for 2-4 cardiac cycles with slow release, noting changes to flow direction and velocity
91
Q

how is oscillations used to asses circle of willis

A
  • short, rapid incomplete compressions, note transmitted oscillation
92
Q

how are velocities in collaterals affected by contralateral CCA compressions

A
  • already increased velocities accentuated
93
Q

what are 3 different collateralization pathways

A
  • crossover/right to left
  • external to internal
  • posterior to anterior
  • vertebrobasilar
94
Q

what is the crossover/right to left pathway

A
  • antegrade flow is evident in ipsilateral ACA
  • due to flow in patent ACoA
  • increased velocities >150% in contralateral ACA are seen
  • MCA velocities decrease with contralateral CCA compression
95
Q

what is the external to internal pathway

A
  • retrograde flow is seeing the ipsilateral ophthalmic artery
  • due to flow form ECA branches that communicate with ophthalmic
  • confirmed by noting reduction, obliteration, reversal of opthalmic flow with ipsilateral ECA compression
96
Q

what is the posterior to anterior pathway

A
  • flow velocities in ipsilateral PCA exceed that of the MCA by 125%
  • increased flow velocities with compression of the CCA confirm this finding
97
Q

what is the vertebrobasilar pathway

A
  • circulation abnormalities due to subclavian steal are uncommon
  • basilar artery flow may be reduced or show a “to and fro” pattern if both vertebral arteries are diseased
  • revered flow is rarely seen
  • subclavian steal is a benign condition
98
Q

what will arteries look like with an AV malformation AVM

A
  • increased systolic and diastolic velocities
  • adjacent arteries have decreased flow
  • reduced pulsatility
  • velocities as high as 280
  • little response to CO2 stimulation
99
Q

what is intraoperative monitoring

A
  • monitoring blood flow during endarterectomies and bypass surgery
100
Q

what does intraoperative monitoring detect

A
  • rapid changes in flow which alert surgeon to possible complications that alter operative technique
101
Q

which vessel is monitored with intraoperative monitoring

A
  • MCA giving information about cerebral perfusion
102
Q

what MCA velocity indicates adequate collateral flow during intraoperative procedure

A

> 10cm/sec

103
Q

what is the most frequent application of transcranial doppler

A
  • detecting vasospasm
104
Q

what is a spasm of cerebral arteries a complication of

A
  • subarachnoid hemorrhage
105
Q

where does a SAH occur

A
  • between the arachnoid and Pia mater layers of the cerebrum
106
Q

are vasospasms asymptomatic or symptomatic

A
  • mild can be asymptomatic, but severe reduces cerebral perfusion and symptomatic ischemic deficit can result
107
Q

what are the symptoms of vasospasm

A
  • confusion
  • decreased levels of consciousness
  • stroke
108
Q

where do vasospasms occur relative to the aneurysmal side

A
  • can occur ipsilateral or contralateral to the side of the aneurysm or bilaterally
109
Q

when does vasospasm usually occur

A
  • 4-14 days post hemorrhage
110
Q

what does an MCA velocity >120cm/sec indicate

A
  • reaction to a documented hemorrhage
111
Q

what does an increase of >20cm/sec per day in the MCA velocity indicate

A
  • poor prognosis
112
Q

what is an MCA velocity >200cm/sec associated with

A
  • critical reduction in cerebral blood flow
113
Q

what is an alternative method of diagnosis of vasospasm

A
  • angiography
114
Q

what three things is the determination of brain death is based on

A
  • clinical status
  • EEG results
  • angiographic demonstration of absent intracranial circulation
115
Q

what does spectral signals progressing toward brain death show

A
  • decrease in diastolic flow

- eventually reaching zero

116
Q

what will signals show just prior to brain death

A
  • reversed flow with a to and fro motion that is easily detected on a TCD spectral tracing
117
Q

how does systolic velocity change with brain death

A
  • decreases to the end result of no flow in the brain
118
Q

what is functional reserve testing

A
  • evaluates the reserve mechanism of cerebral vasculature in the presence of carotid occlusive disease using O2 stimulus
119
Q

what vessel is monitored with functional reserve testing

A
  • MCA
120
Q

what is the normal response to functional reserve testing

A
  • peripheral vascular bed should dilated in response to hypoxia and flow in MCA should increase
121
Q

what is the abnormal response to functional reserve testing

A
  • no change with CO2 stimulus this indicates peripheral beds are already maximally dilated therefore exhausting the vasomotor reserve
122
Q

what is sickle cell anemia

A
  • genetic defect of hemoglobin synthesis

- sickle shaped RBCs clump together

123
Q

what are patients with sickle cell at risk for

A
  • strokes
124
Q

what vessel velocities are investigated with sickle cell anemia

A
  • MCA velocities
125
Q

what MCA velocities indicate risk of stroke with sickle cell anemia

A
  • > 200cm/sec

- patient should receive transfusions

126
Q

what is emboli

A
  • particulate matter can arise from carotid system plaque, heart tumors, or thrombus
  • air emboli can occur during operative procedures
127
Q

what is emboli detection also called

A
  • micro emboli signals, or high intensity transient signals
128
Q

what value is considered serious for emboli detection increasing risk of stroke

A
  • > 50HITS over a 10 minute period
129
Q

what are three criteria for emboli detection

A
  • duration usually <300cm/sec
  • unidirectional signal within the doppler velocity spectrum
  • signal is accompanied by snap or chirp on the audible output
130
Q

what is a patent foramen ovale PFO

A
  • abnormal right to left blood shunts in the heart that bypasses the pulmonary artery and lungs
131
Q

what is a potential complication from PFO

A
  • potential for venous thromboemboli ending up in the peripheral arterial system or in the cerebral vasculature
132
Q

how does TCD detect PFO

A
  • micro for bubbles are injected into a superficial vein in the arm during bilateral monitoring of the MCA blood flow
  • foramen ovale is closed the bubbles fo to the lungs
  • foramen ovale is open the bubbles will cause HITS in the MCA after a few seconds

Vascular 3 (3 decks)

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