Vertebral Artery Atherothrombosis Treatment & Management

Updated: Jan 16, 2016
  • Author: Mark D Morasch, MD, RPVI; Chief Editor: Brian H Kopell, MD  more...
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Treatment

Medical Therapy

Patients with symptomatic vertebrobasilar ischemia who cannot be treated with surgery or investigational endoluminal therapy may be treated medically with antiplatelet agents or with long-term anticoagulation to prevent thrombosis.

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Surgical Therapy

Previous experience has shown that with appropriate diagnosis and surgical correction, complete resolution of hemodynamic and embolic symptoms can occur predictably. Vertebral artery reconstruction can be performed successfully with fewer ischemic complications than carotid artery surgery and with durable long-term results. [20, 21] The location of disease dictates the type of surgical reconstruction required.

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Intraoperative Details

The main option for treating offending ostial lesions (V1 segment) is transposition of the proximal vertebral artery onto the common carotid artery.

Elective surgical reconstruction is very rarely undertaken within the V2 segment; however, ligation (at the C1-C2 level) and bypass to the distal (V3 segment) vertebral artery may be indicated. Extrinsic lesions can be corrected to relieve kinking or compression of the artery. The most common indication for exposure of the V3 segment of the artery is for control of hemorrhage. An alternative for traumatic injuries to the V2 segment includes coil embolization.

Reconstruction of the distal (V3 segment) vertebral artery is usually performed at the C1-C2 level. The techniques most often used to reconstruct the distal vertebral artery at this level include (1) saphenous vein bypass from the common carotid, subclavian, or proximal vertebral artery; (2) transposition of the external carotid or hypertrophied occipital artery to the distal vertebral; and (3) transposition of the distal vertebral artery to the side of the distal internal carotid artery. [19]

More distal pathology can be accessed surgically above the level of the transverse process of C1. Surgical exposure at the suboccipital segment requires resection of the C1 transverse process and part of its posterior arch. Reconstruction at this level is limited to saphenous vein bypass from the distal internal carotid artery.

Exposure and transposition of the vertebral artery into the common carotid artery

The approach to the proximal vertebral artery is the same as the approach for a subclavian to carotid transposition. The patient is positioned in a slight chair position to decrease venous pressure and to allow optimal visualization of the anatomy at the base of the neck. The incision is placed transversely about a finger’s breadth above the clavicle and directly over the two heads of the sternocleidomastoid muscle. Subplatysmal skin flaps are created and dissection is carried down directly between the two bellies of the sternocleidomastoid. The omohyoid muscle is divided with electrocautery. The jugular vein is mobilized laterally and the vagus nerve is retracted medially with the common carotid artery. The carotid should be exposed proximally as far as possible and well behind the ipsilateral clavicle.

On the left side, the thoracic duct is divided between ligatures. Accessory lymph ducts, often seen on the right side of the neck, are also meticulously identified, ligated, and divided. The entire dissection is confined medial to the prescalene fat pad that covers the scalenus anticus muscle and phrenic nerve. These structures are left unexposed lateral to the field. The vertebral vein emerges from the angle formed by the longus colli and scalenus anticus and overlies the proximal vertebral artery. It is ligated and divided. The vertebral and subclavian vessels are now visible.

Identifying and avoiding injury to the adjacent sympathetic chain is important. The vertebral artery is dissected superiorly up to the level of the tendon of the longus colli and inferiorly to its origin from the subclavian artery, exposing 2-3 centimeters of length. The vertebral artery is freed from the sympathetic trunk resting on its anterior surface without damaging the trunk or the ganglionic rami. After dividing the vertebral artery at its origin, it can be transposed to a position anterior to the sympathetics without causing them harm.

Once the artery is fully exposed, an appropriate site for reimplantation in the common carotid artery is selected. The patient is given systemic heparin. The distal portion of the V1 segment of the vertebral artery is clamped below the edge of the longus colli. The proximal vertebral artery is ligated immediately above the stenosis at its origin using a small monofilament suture as a transfixion stitch. The artery is divided at this proximal level.

The carotid artery is then cross-clamped. An elliptical 5-7 mm arteriotomy is created in the posterolateral wall of the common carotid artery with an aortic punch. The anastomosis is performed in parachute fashion with continuous 7-0 polypropylene suture, avoiding any tension on the vertebral artery, which may easily tear. See the image below.

Anastomosis.

Before completion of the anastomosis, standard flushing maneuvers are performed, the suture is tied, and flow re‑established. See the image below.

An arteriogram following a proximal vertebral to c An arteriogram following a proximal vertebral to carotid artery transposition.

Exposure of the V2 segment of the vertebral artery

The V-2 segment is rarely surgically accessed due to its interosseous position. Direct exposure usually requires resection of the transverse processes of the cervical vertebrae. As such, control may be best affected with proximal and distal ligation of the artery in V1 and V3 segments or via endoluminal coil embolization.

V3 exposure and distal vertebral artery reconstruction

The skin incision is placed in the upper neck anterior to the sternocleidomastoid muscle similar to the incision used for carotid endarterectomy. The dissection proceeds between the jugular vein and the anterior edge of the sternocleidomastoid, exposing the retrojugular portion of the spinal accessory nerve. The nerve is followed proximally as it crosses in front of the jugular vein and the transverse process of C1. Next, levator scapula muscle is identified by removal of the fibrofatty tissue overlying it. The spinal accessory nerve must be protected from undue stretch during this portion of the dissection.

Once the anterior edge of the levator muscle is exposed, the anterior ramus of C2 is visible. This nerve is easily identifiable and marks the accessible segment of the vertebral artery. With the ramus as a guide, a right-angle clamp is slid under the levator scapula and over the ramus, and the muscle is elevated. The muscle is transected from its insertion on the C1 transverse process. The C2 ramus divides into 3 branches after crossing the vertebral artery. The nerve trunk should be cut before it branches. Once the ramus has been divided, the vertebral artery can easily be identified. Division of the C2 ramus may leave the patient with minor posterior scalp numbness but is otherwise a benign manuever. The artery is freed from the surrounding venous plexus using bipolar cautery.

Once the vertebral artery is exposed circumferentially at this level, the common carotid artery is dissected and prepared as inflow for a bypass graft. The location selected for the proximal anastomosis of the bypass graft should not be too close to the bifurcation because cross-clamping at this level may fracture underlying atheroma. Because the distal anastomosis is completed first, a valveless segment of vein or a radial artery conduit facilitates back-bleeding of the vertebral artery for purposes of flushing debris.

The patient is administered intravenous heparin. The vertebral artery is elevated gently and controlled using a small J-clamp. This isolates a short segment for an end-to-side anastomosis. The vertebral artery is opened longitudinally over a short length adequate to accommodate the spatulated end of the bypass conduit. The end-to-side anastomosis is completed with continuous 8-0 monofilament suture. A vascular clamp is placed in the vein graft proximal to the anastomosis, the J-clamp removed and flow reestablished through the vertebral artery.

The proximal end of the graft is passed behind the jugular vein and in proximity to the side of the common carotid artery. The common carotid artery is then cross-clamped, an elliptical arteriotomy is made with an aortic punch, and after cutting to appropriate length, the proximal end of the graft is anastomosed end-to-side to the common carotid artery. Before the anastomosis is completed standard flushing maneuvers are performed. The vertebral artery can be occluded with a clip placed immediately below the anastomosis to create a functional end-to-end anastomosis. This maneuver should be performed to avoid competitive flow or the potential for recurrent emboli.

When no suitable conduit can be identified, the external carotid can be debranched and used as an autograft to the distal vertebral artery. Alternatively, with appropriate exposure and length, the vertebral artery can be transposed, end-to-side, into the internal carotid artery.

Endovascular therapy

In the last decade, endovascular treatment of vertebral artery disease, usually with stent placement, has gained favor as an alternative to surgery. Endovascular access to the vertebral artery is relatively straightforward. The procedure can be performed under local anesthesia, enabling continuous neurological monitoring of the patient. Most cases are performed from a femoral approach, although transbrachial and transradial access has also been used. The stenotic lesions are crossed and treated with 0.014-inch or 0.018-inch guidewires and small coronary-diameter balloons and stents. Procedures can be performed with or without the assistance of embolic protection although most vertebral arteries are too small to accommodate most distal protection devices.

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Postoperative Details

Intra-operative completion imaging using digital angiography is useful and should be considered for all types of vertebral artery reconstruction. Reparable technical flaws may be identified and repair can prevent reconstruction failure.

Postoperatively, patients should be monitored and should receive long-term antiplatelet therapy (eg, aspirin).

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Follow-up

Follow-up care and monitoring is primarily based on clinical assessment of recurrent symptoms. The presence of new symptoms consistent with vertebrobasilar ischemia mandates imaging studies as previously outlined.

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Complications

The perioperative complication rates differ for proximal versus distal vertebral artery repairs. The technically easier proximal operations have been reported to have a combined morbidity/mortality rate of 0.9%. Distal reconstructions have a combined morbidity/mortality rate of 3-4%. [22]

Risk is generally increased when patients undergo a combination of both vertebral and carotid revascularization. Perioperative complications for proximal V1 reconstruction include immediate thrombosis (1.4%), vagus and recurrent laryngeal nerve palsy (2%), Horner syndrome (8.4-28%), lymphocele (4%), and chylothorax (5%), [23] as well as rarely stroke or hematoma. The occurrence of ptosis (drooping of the eyelid) on the operative side is a known complication of proximal vertebral artery reconstructions. This condition is usually temporary and is attributed to a traction injury of the lower cervical sympathetic nerves. For distal reconstructions complications include stroke, hemorrhage, thrombosis and nerve injury (spinal accessory nerve).

Periprocedural risks for endoluminal therapies include access complications, distal embolization and stroke, arterial rupture, stent malposition and vessel thrombosis or dissection. Later, restenosis and stent fracture are not uncommon. Late stent fracture with concomitant in-stent restenosis appears to also be a problem plaguing endoluminal therapies that target lesions at the vertebral artery origin. Anatomically, the vertebral takes origin from the subclavian artery at a near right angle. In addition, the first portion of the subclavian artery has relative mobility while the vertebral becomes fixed at is passes into the transverse foramen of C6. This particular anatomy may create unique mechanical forces that make stent fracture more likely than other parts of the body. See the image below.

Vertebral stent fracture with in-stent restenosis. Vertebral stent fracture with in-stent restenosis.
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Outcome and Prognosis

Open surgical intervention

Results following both proximal and distal vertebral artery reconstructions are generally equal to or better than those reported for other forms of cerebrovascular revascularizations. In experienced hands, the combined stroke and death rates are 4% or less. Long-term patency of the reconstructions is excellent. More than 80% of patients experience symptom relief following surgical reconstruction.

Long-term outcomes of open revascularization for vertebral artery disease are generally excellent with high stroke-free survival rates and patency as high as 90% at 10 years. [24, 25] Although the number of studies is limited and these reports consist of only medium-sized case series, the results seen with open vertebral reconstruction should be considered benchmarks upon which endoluminal therapy should be compared.

Endovascular intervention

Despite high technical success rates, angioplasty alone appears to have unacceptably high rates of restenosis. Adjuvant stent placement seems to add to the clinical durability, but adds inherent morbidity such as malposition and potential stent fracture.

Eighteen patients with extracranial vertebral artery disease in The Stenting of Symptomatic Atherosclerotic Lesions in the Vertebral or Intracranial Arteries (SSYLVIA) Trial underwent angioplasty and stenting. Technical success (determined as less than 50% residual stenosis following treatment), was achieved in 17 (94%) of the 18 patients. There were no periprocedural neurological complications. The investigators, however, reported 6-month restenosis rates of 50%. These recurrences were symptomatic in 39% of cases. [26]

In their series of 105 patients who underwent endovascular stenting for symptomatic vertebral artery disease, Jenkins et al achieved 100% radiographic improvement (residual stenosis ≤30%). The authors reported immediate (30 d) periprocedural risk of death of 1% and periprocedural complication rate of 4.8%. Complications included transient ischemic attack, flow-limiting dissection, hematoma, and catheter-access-site problems. At 1 year of follow-up, six patients had died and five had experienced a vertebrobasilar stroke. At approximately 2.5 years of follow-up 70% of patients remained symptom free, but 13% of patients had restenosis requiring retreatment. [27]

Recent Cochrane review identified 313 endovascular interventions for vertebral artery stenosis, with just over half of the interventions using stent placement as part of the treatment of vertebrobasilar stenosis. The 30-day risk of TIA or stroke was 3.2% and death rate was also 3.2%. [28] The technical success rate was 95%.

As with open surgical techniques, mostly retrospective case series exist for endoluminal therapies for the treatment of vertebral artery disease. No level 1 data support the routine application of angioplasty and stenting of the vertebral artery over best medical therapy. A subset of 16 patients treated within the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS 2001) represents the only report of a randomized controlled trial comparing endoluminal therapy with best medical care for symptomatic vertebral stenosis. No 30-day strokes or deaths were reported in either group, although 2 of 8 patients who underwent endoluminal therapy experienced transient ischemic symptoms. Furthermore, with a mean follow-up of 4.5 years, no posterior circulation strokes were noted in either group. [29]

Ogilvy et al reported a series of patients with the longest follow up thus far (21 mo) in whom drug-eluting stents were used in vertebral artery origin stenoses. They found decreased incidence of in-stent restenosis (>50% diameter) from 38% in patients who received non-drug-eluting stents to 17% in those who received drug-eluting stents. [30] Other reports also suggest decreased restenosis rates with drug-eluting stents; however, most the studies have mean patient follow-up times less than 1 year. [31, 32] Treatment with drug-eluting stents requires long-term dual antiplatelet therapy, whether differing stent makeup has a significant impact in the outcomes of patients who undergo interventions of the vertebral artery is unclear.

The Vertebral Artery Stenting Trial (VAST) has been undertaken to compare  percutaneous vertebral interventions and medical therapy. The phase 2 VAST was stopped after patients in the stenting group suffered a higher rate of vascular death, myocardial infarction, and stroke (5%) versus the medical treatment group (2%). In addition, after a median follow-up of 3 years, 7 (12%) of patients in the stent group had a stroke in the area of the symptomatic  vertebral artery, as compared to 4 patients (7%) in the medical treatment group. During the complete time of follow-up, there were 60 serious adverse events (8 strokes) in the stent group and 56 such events (7 strokes) in the medical treatment group. As a result of the findings, the VAST investigators concluded that stenting is associated with major periprocedural vascular complications, with the risk of recurrent vertebrobasilar stroke being low with best medical treatment alone. The need for and feasibility of a phase 3 trial was therefore questioned. [33, 34]

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Future and Controversies

Atherosclerotic vertebral artery disease is an underdiagnosed cause of posterior circulation ischemia. Revascularization of the vertebral artery is often a viable option and should be considered in symptomatic patients in whom medical therapy has failed. Modern surgical advances have resulted in a safe and durable mode of therapy for patients with documented symptomatic vertebrobasilar ischemia. Both surgical and endoluminal approaches to treating vertebral artery pathology may be considered and the choice between the two is often determined by the anatomic location of the lesion being intervened upon. Such consideration requires a complete understanding of the vertebrobasilar anatomy using appropriate imaging studies.

Open techniques for revascularization of the vertebral artery have proven clinical durability and acceptable surgical morbidity in experienced hands. Endoluminal techniques, which have gained momentum over the past decade, have shown clinically feasible but have yet to deliver on durability benchmarks set by open surgical revascularization. As such, vertebral artery stenting should be reserved to select centers with high volume experience that have established acceptable outcomes in both clinical success and safety. For each individual patient who suffers from medically refractive vertebrobasilar ischemia, practitioners must carefully balance the risks of surgery versus the limitations of endoluminal intervention before recommending intervention.

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