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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5760_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter 5 · Extracranial Cerebral Arteries
364
5
d
e
. Fig. 5.57 (continued)
. Fig. 5.58a–c (Atlas) Plaque morphology– surface structure (see . Fig.5.15, 7 Sect. 5.6.1).
a Sagittal B-mode image showing inhomogeneous plaques with ill-dened contours. Bright spots suggest that the plaque extends almost to the center of the artery. Color duplex imaging is necessary for adequate evaluation, showing a very small residual lumen between the two plaques on the far
and near wall. Flow acceleration is indicated by aliasing. Type IV plaque: echolucent, inhomogeneous, surface not delineated from vessel lumen.
b Spectral Doppler measurement with the sample volume placed in the stenotic jet conrms high-grade stenosis with a peak systolic velocity
(PSV)>4m/s.
c Intraoperative conrmation of high-grade stenosis with a long plaque, predominantly of the atheromatous type (consistent with the ultrasound ndings)
5.10 · Atlas: Extracranial Cerebral Arteries
. Fig. 5.59a–c (Atlas) Plaque
morphology– long concentric
carotid stenosis (smooth, regular surface).
a Gray-scale image depicting a
concentric, fairly homogeneous
and smoothly marginated plaque
in the center with a just barely
visible, extremely echolucent
portion extending cranially. Only
the color duplex image enables
dierentiation of the echolucent
distal plaque portion and perfused lumen. The peak systolic
velocity (PSV) determined by
spectral Doppler measurement is
230cm/s.
b Angiogram conrming a long
concentric, smooth stenosis.
c Intraoperative photograph
showing mostly brous plaque
with a smooth surface (for this
plaque composition, a higher
echogenicity would have been
expected in the preceding ultrasound examination)
365
5
366
Chapter 5 · Extracranial Cerebral Arteries
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. Fig. 5.60a–c (Atlas) Plaque morphology– high-grade stenosis with ulceration.
a Echolucent plaque (P) with ulceration (U) at the internal carotid artery (ICA) origin. The concentric plaque causing high-grade stenosis begins
directly distal to the ulceration. Ulceration often occurs in the proximal portion of a highly stenotic plaque protruding far into the lumen. The
arriving pulse wave (often depicted as longitudinal pulsatile plaque movement by gray-scale imaging) may cause rupture of the vulnerable
plaque cap. In the example, the peak systolic velocity (PSV) in the stenotic jet (indicated by aliasing) is 220cm/s.
b Angiography with a lling defect conrming the plaque contour demonstrated by ultrasound and also the ulceration.
c Intraoperatively, the atheromatous plaque and adjacent ulceration are conrmed at the sites already identied by ultrasonography and
angiography
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5
a
Ophthalmic artery
Supratrochlear artery
Internal carotid artery
Facial artery
External carotid artery
c
. Fig. 5.61a–e (Atlas) ICA occlusion.
a Patient with occlusion of the internal carotid artery (ICA) indicated by the absence of ow signals both in the color ow image and in the Doppler waveform. There is a calcied plaque with acoustic shadowing at the ICA origin. The common carotid artery (CCA) is patent (right part of color ow image). To
dierentiate occlusion from subtotal occlusion, the ICA must be scanned to the level of the mandibular angle using high gain to detect low ow.
b In this patient, the external carotid artery (ECA) provides collateral ow via the supratrochlear artery, resulting in a larger diastolic ow component
in the ECA waveform. To avoid confusion with the ICA in this situation, the identity of the ECA should be conrmed using the temporal tap maneuver. Rhythmical tapping of the temporal artery (branch of ECA) causes oscillation in the ECA waveform (as shown here) but not in the ICA waveform.
c Diagram of collateralization of ICA occlusion via the ECA and supratrochlear artery (CW Doppler).
d Angiogram: ICA occlusion (arrow).
e In ICA occlusion, ow in the CCA becomes more pulsatile with a Doppler waveform becoming more like that of the ECA, the only artery supplied
by the CCA in this situation (known as externalization of the CCA)
Common carotid artery
d
b
e
. Fig. 5.62 (Atlas) Signs of recanalization in ICA occlusion.
When examining a patient with suspected internal carotid artery (ICA) occlusion, the examiner must search for ow signals using a low pulse repetition frequency (PRF). Recanalization is uncommon and must be dierentiated from pseudo-occlusion. The latter is characterized by a patent
poststenotic segment of normal width with very slow ow lling most of the lumen, while isolated high-frequency ow signals may be identied
in the subtotally occluded segment when high gain is used. In occlusion with recanalization (as in the case presented here), ow signals indicating a thin, meandering current are depicted centrally in the otherwise occluded and shrunken extracranial ICA, which is often lled with more
hypoechoic residues marginally. Unlike stenotic narrowing, recanalization is characterized by slow ow (23cm/s in the example with atypical ICA
ow signal due to changed resistance). The meandering recanalization channels can disappear from the scan plane, which should not be misinterpreted as absence of blood ow in the color ow image (artifact farther away from transducer due to low PRF)
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Chapter 5 · Extracranial Cerebral Arteries
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. Fig. 5.63a–c (Atlas) CCA occlusion– collaterals.
a In patients with occlusion of the common carotid artery (CCA) and a patent bifurcation, the internal carotid artery (ICA) is relled via branches
of the external carotid artery (ECA), primarily the superior thyroid artery, which in turn is supplied by branches of the thyrocervical trunk.
b Distal ECA branches may likewise contribute to the supply of the ICA.It is therefore common to see retrograde ow in a long segment of the
ECA (displayed in red, toward the heart, same ow direction as in the accompanying internal jugular vein).
c ICA with forward ow (displayed in blue, away from transducer). The ICA waveform (like the waveform from the ECA) shows postocclusive ow
with damping and a delayed systolic upstroke
ab
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c
. Fig. 5.64a–d (Atlas) Complete extracranial carotid territory occlusion.
a When the common carotid artery (CCA) is occluded, the examiner should begin by identifying the bifurcation and then try to detect ow in the
internal carotid artery (ICA) and external carotid artery (ECA). Evaluation is limited when large plaques with acoustic shadowing are present. An
occluded segment appears very heterogeneous and contains areas of higher echogenicity, making it dicult to delineate the arterial lumen from
the surrounding connective tissue. The arteries are indicated by calipers (CCA: D1; ICA: D2; ECA: D3). The only patent vessel with ow (blue) is a vein
in the top right corner of the image.
PPHA as collateral in ICA occlusion.
b Atherosclerotic occlusion (2cm in length) of the mid-segment of the ICA.The distal ICA receives blood supply via a persistent primitive hypoglos-
sal artery (PPHA).
c Flow velocity in the postocclusive segment of the ICA is markedly reduced (peak systolic velocity (PSV) of 10cm/s).
d The PPHA with red-coded ow toward the heart (PSV of 40cm/s) rells the proximally occluded ICA
d
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. Fig. 5.65a-f (Atlas) Occlusion of the brachiocephalic trunk– collateral pathways.
Duplex ultrasound allows excellent hemodynamic evaluation of collateral channels.
a There is alternating forward and backward ow in the common carotid artery (CCA) with predominantly orthograde diastolic ow and slow retrograde systolic ow (blue-coded ow toward the brain in the CCA, red-coded ow in the jugular vein).
b Alternating ow directions (red/blue) in the internal carotid artery (ICA) with orthograde ow during diastole and rather high retrograde ow
during systole (red, toward transducer; peak systolic velocity (PSV) of 50cm/s) indicate that the ICA has been recruited as a collateral and supplies
the ECA territory via the intracranial circulation during systole.
c The retrograde systolic ow in the ICA rells the ECA, where the ow direction is normal and the waveform shows postocclusive ow.
d There is retrograde ow in the vertebral artery (A.VERT), which supplies the subclavian artery (A.S) (SA=mirror artifact; oscillations from tempo-
ral tap in the waveform during diastole).
e The resupplied subclavian artery shows postocclusive ow.
f The MR angiogram shows occlusion of the brachiocephalic trunk and provides a (morphologic) overview of collateral pathways but– unlike
spectral Doppler– no information on the relative ow contributions of the individual collaterals
. Fig. 5.66a–c (Atlas) CCA stenosis.
a Preferred sites of common carotid artery (CCA) stenoses are the origin proximally and the area of the bifurcation distally. In the example, concentric plaques (P) cause high-grade stenosis just before the CCA divides into the internal carotid artery (ICA) and external carotid artery (ECA).
The stenosis is indicated by aliasing in the color ow image and conrmed by spectral Doppler analysis with a peak systolic velocity (PSV) of more
than 4m/s.
b Angiogram conrms the high-grade stenosis of the distal CCA just before the bifurcation.
c With increasing stenosis of the distal CCA, communicating vessels entering the ECA, e.g., via the superior thyroid artery, are recruited as col-
laterals. In the case shown here, high-grade stenosis of the CCA (P) is suggested by aliasing. There is retrograde ow in the ECA (displayed in red,
toward transducer) with relling of the ICA.The Doppler waveform from the ECA shows backward ow to the heart (toward transducer). The large
diastolic component reects the fact that the ECA supplies the brain indirectly via the ICA. (Posterior transducer position as opposed to anterior
position in a)
a b
abc
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. Fig. 5.67a, b (Atlas) High-grade stenosis of the brachiocephalic trunk.
a In a patient after carotid endarterectomy (CEA), the waveform from the internal carotid artery (ICA) shows the typical features of poststenotic
ow (low PSV, delayed systolic rise). Neointimal proliferation is apparent (identied by low echogenicity). These ndings should prompt a search
for stenosis proximally.
b High-grade stenosis of the brachiocephalic trunk with a PSV>3m/s (aliasing technically not avoidable due to high Doppler shift frequency with
acute insonation angle). The sample volume is placed in the stenosis jet (indicated by turbulent ow, encoded in blue). Only a short portion of the
stenotic segment is evaluable because the artery leaves the scanning plane
5
. Fig. 5.68a–c (Atlas) ICA occlusion– compensatory ow increase in collateral pathways.
Occlusion of the internal carotid artery (ICA) is compensated for by larger ow volumes in the collateral arteries. The resulting higher ow velocities must
not be misinterpreted as indicating stenosis. Faster ow is detectable in long segments of the collaterals, while no stenosing structures are identied.
a The ipsilateral external carotid artery (ECA) can become a collateral, seen as internalization of the ECA waveform (to-and-fro ow– knocking waveform
in the bulb).
b Occasionally, there may be an increased compensatory ow in the contralateral common carotid artery (CCA) as well (150cm/s in the case shown).
c PSV of 200cm/s in a long segment of the contralateral ICA.The increase is rarely as impressive as in this case and varies with the contributions of other
collaterals
. Fig. 5.69a, b (Atlas) Pitfall of PSV-based ICA stenosis grading in contralateral ICA occlusion.
a Long echolucent plaque (P; longitudinal image on the left) of the internal carotid artery (ICA) causing <50% luminal narrowing, while the peak
systolic velocity (PSV) of 189cm/s suggests 60–70% stenosis (by ECST criteria). The maximum diameter reduction determined in the ICA in the
transverse plane (right image) is just below 50% (beware of inherent limitations using this method), corresponding to a 50% cross-sectional area
reduction (as the plaque is predominantly eccentric), which is not hemodynamically relevant. Cross-sectional area of patent lumen: 0.14cm2; total
cross-sectional area of ICA: 0.3cm2.
b To determine whether the increased PSV in the ICA is due to an increased blood ow volume to compensate for contralateral ICA occlusion,
ow velocity in the common carotid artery (CCA) is measured. In the example, a high PSV of 97.2cm/s in the CCA indicates that at least part of the
PSV increase in the ICA is attributable to collateral ow. Consequently, the PSV in the ICA overestimates stenosis severity and, to arrive at a correct
estimate, allowance must be made for the contribution due to collateral ow
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a cb
. Fig. 5.70a–c (Atlas) Suture aneurysm.
a Pulsatile mass of the neck 3years after carotid endarterectomy (CEA). Color duplex sonography identies a circumscribed outpouching with
ow signals in the patch area at the origin of the internal carotid artery (ICA). Incomplete color lling of the pouch suggests partial thrombosis. No
demonstration of stenosis.
b Angiogram conrms saccular aneurysm of the ICA bulb.
c Intraoperatively, a suture aneurysm covered by connective tissue structures is seen with thrombotic deposits in the aneurysmal sac (arrowhead)
. Fig. 5.71 (Atlas) Complications after carotid endarterectomy– suture aneurysm.
Virtually all pseudoaneurysms of the carotid system are due to trauma or occur in the form of suture aneurysms after carotid endarterectomy
(CEA), particularly in patients who have undergone synthetic patch angioplasty. Suture aneuryms often indicate infection of the patch. The
longitudinal (left) and transverse color ow images (right) show a conspicuous mushroom- like structure protruding from the vessel, which can
be palpated as a pulsating mass in most cases. The color coding varies with the presence and extent of thrombosis. The spectral waveform from
the aneurysmal neck shows the typical to-and-fro sign indicating high-frequency systolic ow into the aneurysm and ow into the carotid lumen
throughout diastole
ab
ef
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c
. Fig. 5.72a–f (Atlas) True ICA aneurysm.
a Transverse image showing the patent lumen of the internal carotid artery (ICA) surrounded by hypoechoic aneurysmal thrombotic deposits
(arrowheads) both in the bulb area (left) and in the distal segment (right). The aneurysm has a diameter of 2cm.
b The longitudinal image allows evaluation of the shape of the ICA aneurysm (common carotid artery (CCA) on the right and ICA on the left). The
image impressively shows the total extent of the aneurysm (arrowheads) and the size of the hypoechoic thrombotic portion in relation to the
color-coded patent lumen. The color change indicates eddy currents.
c At the distal end of the aneurysm there is ow acceleration with turbulence and aliasing (inverted display). Flow velocity is increased to 2.9m/s
(inverted waveform depicting ow away from transducer above the baseline).
d Angiogram: Ectasia of the ICA.The mural thrombi make the aneurysm appear smaller than it actually is, and angiography does not provide
information on the hemodynamic signicance of the stenosis at the distal end of the aneurysm; all that is seen is less pronounced opacication
due to luminal narrowing in the anteroposterior projection.
e Intraoperative site conrming the spindle-shaped aneurysm of the proximal ICA with mural thrombosis and brotic stenosis at its distal end
(arrowhead). CCA with shunt on the right and distal ICA on the left with the aneurysm of the proximal ICA in between. The aneurysm is thrombosed and shows brous luminal narrowing at its distal end. A blue vascular sling is placed around the ECA.
Mycotic ICA aneurysm.
f Transverse (left) and longitudinal (right) images of a saccular aneurysmal dilatation (AN) of the proximal ICA.The transverse view nicely depicts
the aneurysm with ow toward the transducer (red). Flow direction in the ECA is normal (blue, toward the head)
d