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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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76 CAROTID TREATMENT: PRINCIPLES AND TECHNIQUES
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3-1
Low Bifurcation of the Carotid
Artery with Symptomatic
Plaque Just at the Origin of the
Internal Carotid Artery
AP (A) and lateral (B) radiographs of common carotid injection are shown. In this case, the carotid bifurcation
is just in front of the body of the C5 vertebra and the plaque does not ascend higher than the C4-5 disc space.
Difculties can arise with an exposure at this low level, where the carotid artery dives deep to the sternocleidomastoid and omohyoid muscles. Anatomic structures that will be encountered and probably divided include
the omohyoid muscle (see Figs. 4-25 and 4-28) and some accessory branches from the jugular vein that are
similar to the common facial vein but about 3 inches lower in anatomic location (Fig. 4-14). The difculties with
a low bifurcation of this type are: (i) securing enough exposure of the common carotid artery (CCA) to ensure
adequate placement of the Rummel tourniquet and (ii) cross-clamping below that site in case placement of an
indwelling shunt is needed. In the AP view (A), the internal carotid artery (ICA) swings laterally and thus a
standard operating position will sufce. No unusual degree of head turning is required to adequately expose
the ICA in this case.
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3-2
High Bifurcation of the Cervical
Carotid Artery
These lateral radiographs (A, conventional; B, subtracted; C, digital) of a CCA injection demonstrate what I
consider to be a relatively high bifurcation and high extension of the plaque into the ICA. Two major landmarks
give some clue as to the degree of difculty of the high exposure, although it is never possible to determine with
certainty just how high the surgical exposure will need to extend. The rst of these landmarks is the angle of
the mandible, which can be palpated and marked before the skin incision (A), thereby giving some clue as to
the degree of difculty that will be encountered in the exposure. The second anatomic landmark is the position
of both the bifurcation and the distal extent of the ICA plaque in relation to the cervical section of the spine. In
this case, the bifurcation is at the level of the body of C2, and the ICA will need to be exposed at about the C1-2
junction. As emphasized elsewhere in this text, the cardinal principle regarding the ICA is that control must be
obtained well distal to the top of the plaque before any consideration of ICA cross-clamping. Failure to do this
could result in either embolization of material from cross-clamping or the inability to place a shunt above the
area of atheroma, with possible particulate embolization during insertion of the shunt.
A number of surgical strategies must be used when a high bifurcation is encountered, and they will be discussed in greater detail elsewhere in the book (Figs. 4-30 to 4-32). My basic philosophy is that the surgeon needs
to be prepared for a high exposure in essentially every carotid surgical procedure. It is far simpler to have the
carotid artery well exposed from the beginning than trying either to work up a dark tunnel or to go back and recreate the exposure in the middle of the procedure. The skin incision thus goes high and behind the ear in nearly
every case (Fig. 4-5), and the anterior border of the sternocleidomastoid muscle is dissected to expose the high
jugular vein (Figs. 4-31 and 4-32). A plane of dissection is developed between the jugular vein and the ICA. In an
exposure as high as the one illustrated here, the hypoglossal nerve will be mobilized (Fig. 4-29) and the digastric
muscle most likely will be at least partially transected (Figs. 4-31 and 4-32). The use of the hinged retractor is
particularly important in securing a well-lighted and well-exposed high exposure of the ICA.
I cannot emphasize strongly enough the importance of having the ICA properly exposed before arterial
cross-clamping, possible shunting, and arterial repair. There is no worse situation in my mind than having a
major electroencephalographic (EEG) change with an inadequately exposed ICA and desperate attempts to
increase ICA exposure under this type of pressure.
Incidentally, it should be noted that this patient has an accessory artery (probably the ascending pharyngeal) arising from the crotch of the carotid bifurcation. It is important to identify these anomalies on pre-operative
angiography because failure to recognize and isolate this type of artery will result in extremely troublesome
backbleeding during the arteriotomy and arterial repair. The identication of arteries such as this (which occur
in my experience in approximately 5% of cases) is one of my strongest arguments in favor of conventional arteriography and against the use of magnetic resonance angiography or ultrasound alone in the pre-operative evaluation of symptomatic carotid patients. (See Figs. 4-36 and 4-37.)
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3-3
Side-by-Side
An anatomic variant that warrants special pre-operative considerations is what I call the “side-by-side” carotid
artery positioning, as illustrated in these AP (A) and lateral (B) views. Whereas the ICA in the AP plane usually lies directly behind the external carotid artery (ECA) or else is rotated somewhat laterally, in a side-by-side
carotid artery, it swings medially and is tucked underneath the ECA as it courses medially. Invariably, there
is a large kink with a lateral bend of the ICA at a somewhat higher level than is usually exposed surgically, as
illustrated here by the arrow in the AP view. This type of bend can hamper shunt placement and should be recognized pre-operatively.
A side-by-side carotid artery represents a more difcult anatomic dissection. In a case such as the one
illustrated here, it is necessary to turn the head radically to the opposite side from the surgical incision, thereby
swinging the ICA as far lateral as possible. Unfortunately, this process of head turning also brings the sternocleidomastoid muscle into such a position as to overlie the CCA and carotid bifurcation, and a much greater degree
of retraction of both the sternocleidomastoid muscle and the jugular vein is necessary. I also often nd it necessary to extensively mobilize the ECA in a side-by-side carotid exposure and dissect much farther around the
circumference of the artery than is customarily necessary. This is done to mobilize the ECA medially and allow
it to be tacked up by its adventitia if necessary. All these maneuvers are designed to pull the ICA back out from
its underlying position to the point where it pops out into a more standard anatomic exposure. (See Figs. 4-4
and 4-33.)
Exposure and mobilization of the ICA must be signicantly higher than the extent of the plaque, usually
up to the area of the artery’s lateral bend, as illustrated in the AP view by the arrow (so that the ICA essentially
jumps out into a more normal position). Another strategy for accomplishing this is to tack the adventitia of the
ICA laterally, once again holding it out in place for the arteriotomy.
It is tempting to consider a reverse style ICA arteriotomy—that is, leaving the side-by-side carotid artery
in the position it was found and opening the ICA up its medial side rather than the customary lateral opening,
although I have never had occasion to do this. Instead, I prefer to mobilize the ICA out into a more normal position and then perform the standard lateral wall common and internal carotid arteriotomy and repair.
The signicance of the side-by-side carotid anatomy is that it is possible with pre-operative recognition to
plan positioning in such a way that a potentially difcult anatomic situation can be converted to a rather routine
carotid endarterectomy.
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3-4
Focal Internal Carotid
ArteryUlcer
These cases illustrate the importance of relying on both the clinical history and the angiographic information
in deciding which patients are appropriate surgical candidates. In this particular case, AP (A) and lateral (B)
radiographs of the left CCA demonstrated a mildly stenotic lesion but with a rather punctate focal ulcer up in
the ICA. The bifurcation was low, and the repair appeared to be quite simple. The patient had classic symptoms
of transient ischemic attacks (TIAs) stereotypic to the appropriate artery. The photograph here shows the operative specimen in the ICA, which demonstrates the pathologic correlation of a deep focal ulcer with intra-mural
thrombus and corresponds nicely with the radiographic nding.
This type of patient and the clinical presentation illustrate to me that despite our progress with cooperative
trials, there continue to be situations in which clinical judgment and the presentation of the patient will indicate
that symptomatic lesions that are <50% stenotic represent appropriate surgical lesions and should be carefully
considered for carotid artery reconstruction.
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3-5
Deep Ulceration of a Carotid
Plaque
The photographs of the AP (A) and lateral (B) CCA injection were obtained from a patient with symptomatic
right carotid TIAs. Just beyond the carotid bulb, a large pooling of contrast with very little distal ow is seen
yielding an initially somewhat confusing radiographic picture. Although this might be mistaken for a false or
pseudo-aneurysm in a patient who had undergone a previous carotid dissection, in this particular case it proved
to be nothing more than an enormous, deeply ulcerated plaque with pooling of contrast material in a very deep
and ragged ulcer (see pathologic specimen shown). The straightforward surgical technique in this case entailed
no unusual modications.
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