Distal vertebral artery bypass" Technique, the "occipital conncction," and potential uses

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1 Volume 2 Number 4 My 198s Symposium: Surgery of Vertebral Artery patients with vertebral artery stenosis underwent repair. The Joint Study of Extracranial Arterial Occlusion included 4748 patients; multiplc lesions were present in surgically accessible sites in 67.3%. 9 Approximately 22% of the patients harbored a stenosis of the left vertebral artery origin, and 18% had stenosis on the right. Clearly these lesions are not rare. Relief of vertebrobasilar symptoms following revascularization of the carotid bifurcation perhaps accounts for the relative paucity of vertebral artcry surgery. Humphries et al.,10 Wylie and Ehrenfeld, 2 Rosenthal et al.,n and Ford et al.12 have clearly documented the effectiveness of carotid artery repair in the relief of vertebrobasilar and nonspecific cerebral symptoms. Despite these successes, a group of patients with specific, disabling posterior cerebral circulatory symptoms remains who can be helped by direct repair. Some of the patients have occluded carotid arteries, others a single vertebrobasilar connection, and often there exists an incomplete circle of Willis, which thus deprives them of an important collateral blood flow route. In these people direct operations on the vertebral artery often can be performed safely, with low pcrioperative morbidity and mortality rates. 1"2 Although the relief of nonspecific cerebral symptoms is not so reliable as that following carotid artery surgery to control hemispheric symptoms, many of the patients are significantly improved. In the following discussions the various operative methods for repair of the vertebral arterial system are described and the expected results reviewed. REFERENCES 1. Edwards WH, Mulherin Jr JL. The surgical management of proximal subclavian-vertebral artery stenosis. Ann Surg 1980; 87: Wylie EJ, Ehrenfeld WH. Extracranial occlusive cerebrovascular disease. Philadelphia: WB Saunders Co, 1970: Fields WS, Bruetman ME, Weibel J. Collateral circulation of the brain. Monogr Surg Sci I965; 2: Perry MO. Carotid-subclavian bypass. In: Greenhalgh RM, ed. Extra-anatomic and secondary arterial reconstruction. London: Pitman Publishing Ltd, 1980: Hardin CA~ Poser CM. Rotational obstruction of the vertebral artery due to redundancy and extraluminal cervical fascial bands. Ann Surg I963; 158:I Hurvitz SA. Surgical treatment of partial extraluminal occlusion of the vertebral artery. Surg Gynecol Obstet 1976; 143: Hardin CA. Vertebral artery insufficiency produced by cervical osteoarthritic spurs. Arch Surg I965; 90: Rob C. Occlusive disease of the extracranial cerebral arteries. A review of the past 25 years. J Cardiovasc Surg 1978; 19: Hass WK, Fields WS, North RR, Kricheff II, Chase NE, Bauer RB. Joint Study of Extracranial Arterial Occlusion. JAMA I968; 203: Humphries AW, Young JR, Beven EG, LeFevre FA, dewolfe VG. Relief of vertebrobasilar symptoms by carotid endarterectomy. Surgery 1965; 57: I. Rosenthal D, Cossman D, Ledig B, Callow AD. Results of carotid endarterectomy for vertebrobasilar insufficiency. Arch Surg 1978; 113: Ford JJ, Baker WH, Ehrenhaft JL. Carotid endarterectomy for nonhemispheric transient ischemic attacks. Arch Surg 1975; 110: Distal vertebral artery bypass" Technique, the "occipital conncction," and potential uses Ramon Berguer, M.D., Ph.D., Detroit, Mich. Anatomic and radiologic facts relevant to the technique of revascularization of the distal vertebral artery (DVA) constitute the primary focus of this From the Department of Surgery, Wayne State University. Presented at the combined breakfast program of the Society for Vascular Surgery and the International Society for Cardiovascular Surgery, North American Chapter, Atlanta, Ga., June 8, Reprint requests: Ramon Berguer, M.D., Ph.D., Section of Vascular Surgery, Harper-Grace Hospitals, 3990 John Rd., Detroit, MI article. The clinical selection of these patients has been discussed elsewhere. 1 We describe here our technique for the revascularization of the DVA at the C-1 to C-2 spinal level. We emphasize the surgical relevance of the "occipital connection," a collateral pathway that keeps the DVA patent when its proximal segment occludes. Finally, we ponder the advantages of this technique over conventional extra- and intracranial bypass operations in a specific instance of internal carotid artery (ICA) occlusion.

2 622 Journal of VASCULAR SURGERY Symposium:Surgery of VertebralArtery r o~ Fig. 1. "Occipital connection" filling DVA and, in retrograde manner, patent remainder of proximal VA. ICA is occluded. MATERIAL In our experience one in five vertebral reconstructions has required an operation (bypass) at its distal level. We have done 13 distal bypasses and have simplified our technique as we gained experience. This surgical experience is the gist of this article. All patients had symptoms of cerebral ischemia and were studied before and after the operations by arteri0graphy. A N A T O M I C FACTS The vertebral artery (VA) is anatomically divided into four portions, the last one corresponding to its intradural course. From a surgeon's point of view the VA is accessible with reasonable ease in two places of its extradural portion: in its proximal portion (segment I according to the anatomists) and at the space between the transverse processes of C-1 and C-2, Fig. 2. Reconstitution of DVA at C-1 to C-2 level (arrow) via branches of occipital artery. Note stump of proximal VA. Left ICA (*) is occluded. which we will refer to as the level at which the DVA begins. The boundaries and techniques for reconstruction of the proximal VA have been described elsewhere. 2-s The choice of the C-1 to C-2 interspace for reconstruction of the DVA is based on a number of convenient attributes. It is the widest of the bony

3 Volume 2 Number 4 July 1985 Symposium: Surgery of Vertebral Artery 623 ~gaps between C-6, where the VA normally enters the cervical spine, and the atlas. This is important in a surgical field that is deeper and narrower than those in most vascular operations. It is also at this le;eel that the most important collateral pathway enters the VA: the "occipital connection," usually a branch of the occipital artery (Fig. 1). This collateral branch may sometimes derive from the cervical ascending artery. Occasionally both collateral branches from both sources are present. This collateral pathway has the ability to keep the DVA patent when the proximal segment of the VA occludes. This ability to preserve distal patency is the most likely explanation for the rare occurrence of basilar artery thrombosis, and even for the absence of symptoms of vertebrobasilar insufficiency, in pa- :[ :ients in whom either VA is not visualized and who have small or invisible posterior communicating arteries as shown on arteriograms. The role of this collateral connection, comparable to that which links the external and internal carotid systems across the orbit, is relevant to the understanding of brain perfusion in patients with multiple extracranial arterial disease and permits us to use the VA for a distal anastomosis by maintaining patency of the DVA at this level. Finally, a reconstruction at the C-1 to C-2 level bypasses all the common points of bony compression during rotation of the neck. Both in extensive atherosclerotic disease of the VA and in osteophytic extrinsic compression, the distal segment beyond the C-2 level is usually spared from disease. ANGIOGRAPHIC CRITERIA, In general the angiographic criteria that we set in for our VA reconstruction protocols apply to both proximal and distal operations. These criteria arc: 1. First and foremost, if a patient has a "good" and normal VA, there is seldom an indication to operate on the opposite VA. In other words, a good VA is good enough. 2. Only stenoses >75% of the cross-sectional area are considered suitable for surgical treatment. This is an empirical but safe rule. 3. The origin of the VA can be difficult to evaluate angiographically and may need other projections in addition to the usual right and left oblique views. 4. The level of entry of VA into the cervical spine should be determined if a reimplantation of the proximal VA into the carotid artery is planned. Abnormal Lymph Investing Parotid gland i tip n. astoid Fig. 3. Incision and first layer of dissection in exposure for DVA bypass. Sup. th Comm. caroti Int. jugt Digastric Fig. 4. Dissection of accessory nerve and of carotid bifurcation. entry at C-7 often precludes reimplantation of the shortened first segment of the VA. A DVA bypass may be necessary. 5. The presence or absence of a posterior communicating artery should be established. 6. In those rare cases in which bony compression is suspected, views of both VAs with the neck rotated to both sides are needed. 7. If both (or the dominant) VAs are occluded, the demonstration of the "occipital connection" and reconstimtion of the DVA may require delayed subtraction films or digital subtraction techniques (Fig. 2). For this an arch injection is preferable to a selective injection since the supply to this collateral branch

4 624 Symposium: Surgery of Vertebral Artery Journal of VASCULAR SURGERY Digastric C 2 n. hugging vertebral art. Access Co carot Fig. 5. Transverse process of arias can be felt under digastric muscle. Anterior ramus of C-2 is seen emerging from anterior edge of levator scapulae. Nin~trin r: 1 h Ih~rnl~ Jlae guide Fig. 7. Preparation for distal anastomosis. Note DVA has been transposed anteriorly from its original location (left upper insert). Later on (right lower insert) punch arteriostomy will be made in common carotid artery. Fig. 6. Cutting the levator scapula and splenius cervicis at the C-2 to C-1 intertransverse space. may be derived wholly or in part f>om the cervical ascending artery, a branch of the subclavian artery. TECHNIQUE For our first cases of DVA bypass we approached the artery according to the steps described by Henry 6 for ligature of the DVA in his delightful classic book, "Extensile Exposure." It was soon obvious that this muscle-cutting approach was not necessary because the incision used for carotid endarterectomy provided good exposure to the DVA without the need to divide the greater auricular nerve, detach the sternocleidomastoid from its upper insertion or cut part of the splenius capitis muscle, as Henry had advised. Our present technique is as follows: the incision is anterior to the sternocleidomastoid muscle (Fig. 3). The sternocleidomastoid belly is rotated outwardly, the jugular vein inwardly, and the accessory spinal nerve is identified, freed, and slung. The carotid bifurcation is then dissected (Fig. 4). The extent to which the carotid bifurcation is dissected depends, on the type of proximal anastomosis planned. With ~ the sternocleidomastoid belly rotated outwardly, the sharp prominence of the transverse process of C-1 can be palpated in the upper end of the incision behind the digastric muscle (Fig. 5). The next step is to identify the levator scapulae and the underlying and thinner splenius cervicis, both covering the C-1 to C-2 intertransverse space in which the VA lies. The VA is closely hugged by the anterior ramus of C-2 and this nerve is the best guide for the unroofing of this muscular cover. The large ramus emerges from beneath the anterior edge of the levator scapula. A spatula is inserted as a guide over the ramus and across the levator, which is then cut over the guide as close to the transverse process of C-1 as possible (Fig. 6). The segment of muscle between the transverse process of C-1 and C-2 is excised. The ramus and the underlying VA are now visible.

5 Volume 2 Number 4 July 1985 Symposium: Surgery of Vertebral Artery 625 n. Comm, care Fig. 8. Completed common carotid artery to DVA autog- - enous vein bypass graft. Graft is tunneled under jugular vein. The artery is looped above and below the anterior ramus of the C-2 nerve. Magnification (three or more diameters) is necessary here to avoid entrance into the many small veins near thc transverse processes and behind the artery. The occipital collateral or other branches of the VA may enter the back wall of the artery here (Fig. 7) and if so, they should be carefully avoided while the artery is dissected; otherwise troublesome bleeding will follow. At this point systemic heparin is given. A Heifetz dip is placed distally as high as possible below the transverse process of C-1. The proximal VA is occluded with a metal clip, flush with the upper edge of the transverse process of the C-2 vertebra. The VA is then cut above the metal clip and its dis- "tal portion is transposed anterior to the nerve. A small Heifetz clip may bc needed on the occipital collateral branch if it enters the exposed segment of VA. The thin-walled VA is spamlated anteriorly. Regardless of where the proximal graft will originate, the distal end-to-end anastomosis to the DVA is done first; otherwise the posterior half of the suture line can be very difficult to complete. We use 7-0 polypropylenc for this. The graft is then passed below the jugular vein and into the area of the carotid bifurcation where it is anastomosed to the common, external, or ICA or to the stump of an occluded ICA, as may be the case (Fig. 8). For the proximal anastomosis the preferred site is the common carotid artery. A 5 to 6 mm punch arteriostomy is our choice for the proximal end-toside anastomosis. Fig. 9. Postoperative arteriogram of external carotid artery to DVA bypass (between arrows). There was severe stenosis at origin of this single VA that entered spinal C-7 level, which made reirnplantation of its proximal end into common carotid artery difficult. Fig. 10. Angiogram taken 2 years after surgery shows bypass (between arrows) from carotid bulb to DVA in patient with bilateral ICA aplasia whose left VA thrombosed. Note prompt filling of basilar and middle cerebral artery branches, latter through patent posterior communicating artery.

6 626 Symposium: Surgery of Vertebral Artery lournal of VASCULAR SURGERY DISCUSSION In patients who have only one ICA patent and this artery is on the same side that the DVA bypass is done, the external carotid artery may be tapped for a proximal end-to-side anastomosis (Fig. 9). This procedure avoids the need to clamp the single ICA. However, when the graft originates in the external carotid artery, it takes a more transverse course, one that is possibly more prone to kinking. A DVA reconstruction may be indicated on the same side of an occluded ICA, If the latter has occluded and left a suitably soft proximal stump, it may be used as a convenient site for the proximal anastomosis of the graft, provided again that it is only minimally diseased. We have used a soft carotid bulb as a proximal anastomosis in DVA bypasses in two patients with congenital aplasia (Fig. 10) of the ICA. These patients have a normal carotid bulb and a threadlike ICA that does not reach the circle of Willis. The use of the carotid bulb in these cases avoids the need to clamp the functioning common and external carotid arteries. In patients with symptoms who have severe stenosis of the ICA and bilateral VA occlusion a simultaneous reconstruction of the ipsilateral VA seems reasonable at the time of the ICA endarterectomy. Not all patients with vertebrobasilar insufficiency and stenosis of the ICA will be relieved of their symptoms by carotid endartcrectomy alone. Since the endarterectomy of the ICA is to be done, it appears logical to revascularize at the same operation one of the two occluded VAs and thus increase total cerebral blood flow. The proximal anastomosis is done in the common carotid artery; this gives better position for the bypass graft alongside the vessels of the neck. Finally, it is worthwhile to consider the advantages of the technique of DVA bypass over superficial temporal-middle cerebral anastomoses in a specific instance of ICA occlusion. The association of IGA and bilateral VA occlusions is seen in some patients who have advanced extracranial disease. If revascularization is indicated in these patients because of the presence of symptoms of cerebral ischemia, reconstruction of the DVA offers an appealing solution, particularly when a posterior communicating artery can be demonstrated. A 5 mm diameter graft perfusing the basilar artery is likely to deliver a much greater intracranial flow rate than a superficial temporal-to-middle cerebral artery anastomosis donc for the same purpose. REFERENCES 1. Berguer R. Selection of patients, choice of surgical technique, and results with vertebral artery reconstruction. In: Berguer R, Bauer R, eds. Vertebrobasilar arterial occlusive disease. New York: Raven Press, Berguer R, Bauer RB. Vertebral artery reconstruction: A successful technique in selected patients. Ann Surg 1981; 193: Edwards WH, Mulherin JL. The surgical approach to significant stenosis of vertebral and subclavian arteries. Surgery 1980; 87: Imparato AM, Riles TS, Kim GE. Cervical vertebral angioplasty for brain stem ischemia. Surgery 1981; 90: Roon AI, Ehrenfeld WK, Cooke PB, Wylie El. Vertebral artery reconstruction. Am J Surg 1979; 138: HenryAK. Extensile exposure. Baltimore: Williams &Wilkins, Vertebral arterial reconstruction: experience A nineteen-year Anthony M. Imparato, M.D., New York, N.Y. From the Division of Vascular Surgery, New York University Medical Center. Presented at the combined breakfast meeting of the Society for Vascular Surgery and the International Society for Cardiovascular Surgery, North American Chapter, Atlanta, Ga., June 8, Reprint requests: Anthony M. Imparato, M.D., Profess.or of Surgery, Director--Division of Vascular Surgery, New York University Medical Center, 550 First Ave., New York, NY Whether direct vertebral arterial reconstructions are necessary for the relief of symptoms or whether they significantly influence the long-term prognosis in patients who have extracranial occlusive cerebral arterial disease is subject to much debate. Few series report long-term results of vertebral arterial surgery, although reports of early results are available) -4