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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3660_Библиотеки_им_академика_М_И_Перельмана
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96 CAROTID TREATMENT: PRINCIPLES AND TECHNIQUES
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3-11
Tandem Stenosis
These radiographs demonstrate bilateral AP and lateral views of a patient with carotid embolic disease, severe
disease at the carotid bulbs, and tandem stenoses in the cavernous portions of the carotid artery bilaterally. In
previous reports, tandem stenosis of the carotid artery has been considered a relative contraindication to cervical
carotid reconstruction, the rationale being that the runoff from the cervical carotid repair would be inadequate
to improve cerebral perfusion and would lead to a higher propensity for carotid thrombosis following endarterectomy. Several recent reports have disputed this (127, 128) and to my knowledge current thinking suggests
that tandem stenosis should not be considered a contraindication to cervical carotid repair in cases in which
carotid symptomatology can be clearly localized to the cervical carotid artery. There are also reports of so-called
pseudotandem stenoses that have resolved after correction of a tight cervical carotid lesion (129). At present
then, although I am interested in identifying all sites of potential cerebrovascular embolic phenomena, I do not
hesitate to reconstruct the cervical carotid artery with or without the presence of tandem stenosis in patients who
are otherwise believed to be appropriate surgical candidates.
On the left side (A and B), the AP view (A) shows a signicant lesion just above the carotid bulb; the lateral
view (B) shows a tight tandem lesion just before the carotid siphon. On the right side, the ndings are similar,
with a nearly occlusive carotid bulb lesion (C) and a tandem stenosis in the siphon itself (D).
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98 CAROTID TREATMENT: PRINCIPLES AND TECHNIQUES
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3-12
Cross Filling into Contralateral
Middle Cerebral Artery
These AP radiographs (A and B) of both a left (A) and right (B) CCA injection were taken at the same time
sequence following injection. The stenotic and symptomatic lesion is on the right-hand side in this patient. It can
be seen that the contralateral injection lls not only the left-sided middle cerebral artery but crosses over through
the anterior circulation and lls a signicant portion of the right middle cerebral artery. This would indicate that
the non-operative side is clearly dominant and suggests to me that the patient is at relatively low risk during
carotid endarterectomy and most likely will not require shunting.
It should be noted that I monitor the intra-operative situation identically in every case, regardless of the
pre-operative radiographs, and in the present era in which digital angiography and to some extent magnetic
resonance angiography serve as the only pre-operative studies, this kind of information may not be available. I
have always found it comforting to know, however, that at the time of cross-clamping, demonstrable lling into
the middle cerebral artery from the contralateral carotid artery will be available.
A similar situation exists in patients with unilateral carotid occlusion in which it can be demonstrated
that the symptomatic carotid artery—the one that is to be operated on—is the dominant artery and lls both
middle cerebral arteries. In this case, the need for shunting is higher and the surgical team is prepared for a
greater likelihood of intra-operative monitoring changes and shunt placement. In our series, however, using
monitoring-dependent shunting in every case, the shunt rate has been 15% in routine cases yet only 25% in cases
of contralateral occlusion.
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100 CAROTID TREATMENT: PRINCIPLES AND TECHNIQUES
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3-13
Can We Predict the Need
for Shunting?
This patient presented with stereotypic left carotid TIAs and had failed medical therapy. The left cervical carotid
angiogram (A) demonstrates a 99% lesion, appropriate for surgery. There is also an “isolated” left MCA segment
seen on the intra-cranial angiogram (B) which lls only from the affected left CCA. The intra-cranial right carotid
angiogram (C) shows robust lling but no crossover from right to left, presumably from a hypoplastic left A-1
segment.
My shunt rate for CEA, based on EEG criteria, is 15% of cases, increasing to 25% when contralateral occlusion is present. Clearly, most patients will not require shunting, and in my experience, the need for shunting
cannot be reliably predicted by anatomical criteria. In this case, however, the obvious anatomical failure of collateral circulation made shunting seem more likely to us. At cross-clamping, the EEG changed profoundly, and
a routine shunt placement was performed with a good surgical outcome.
Curiously, on this particular day, we had a visiting Japanese neurosurgeon with us observing in the OR,
and his greatest desire was to see how a shunt was placed.
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3-14
Pre-Operative External Carotid
Artery Occlusion
These AP (A) and lateral (B) radiographs demonstrate a patient with a symptomatic stenosis of the common and
internal carotid arteries and a concurrent occlusion, presumably atherosclerotic, of the ECA. At surgery, these
ECAs can occasionally be re-opened with removal of the plaque. Although an ECA occlusion by itself is of little
consequence, it is important to recognize this variant because if it is not possible to surgically re-open the ECA,
the stroke risk is somewhat increased, the reason being that at the conclusion of the surgical procedure, when the
clamps are removed, there is no ECA safety valve through which air and debris can be ushed before re-opening
the ICA. The subject is discussed further in Chapter 4A: Surgical Technique, in the section dealing with the
sequence of clamp removal. (See Fig. 4-90.)
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Internal Carotid Stump
This lateral radiograph demonstrates a CCA stenosis with occlusion of the ICA and a rather large ICA stump
with a patent ECA. In patients who are having ipsilateral transient ischemic symptoms referable to ECA embolization, a stump mechanism can be implicated if several criteria are met. The theory is that thrombosis occurring
within the stump yields embolization of particulate matter up the ECA, through ophthalmic collaterals and into
the intra-cranial circulation.
There are several radiographic characteristics of a stump that support this diagnosis and point the surgeon
toward consideration of a stump repair. These would include the size of the stump (greater than 1 cm), dynamic
appearance of changes in stump conguration on serial arteriography, or evidence of a lling defect within the
stump (indicating active thrombosis).
In this case, this patient was experiencing ischemic retinal symptoms and it was unclear whether the CCA
stenosis or the stump itself was responsible. A common and external carotid endarterectomy and a stump ligation were performed, and the patient was clinically free of symptoms.
Our technique for stump repair is described later (Fig. 6-2). I do not consider it adequate to ligate the stump
externally but believe instead that a formal common and external carotid endarterectomy should be performed
with monitoring as usual. I have occasionally been called on to shunt the common to external carotid artery during this repair and on rare occasions have been able to re-open an ICA, which of course represents the ideal situation. I feel strongly that symptomatic carotid stumps should be explored since they represent a low-risk, simple
surgical procedure with the possibility of signicant benet.
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