Carotid-Vertebral Artery Bypass for Symptomatic Vertebral Artery Pseudoaneurysm
Article Outline
Abstract
We report a case of an embolizing proximal vertebral artery aneurysm repaired successfully with reversed saphenous vein graft in the presence of a hypoplastic contralateral vertebral artery. This case illustrates surgical and anaesthetic issues faced with vertebral artery aneurysm repair in order to exclude the aneurysm while maintaining adequate cerebral perfusion.
Keywords: Vertebral artery, Pseudoaneurysm, Stroke, Bypass surgery, Neuroanaesthesia
1. Introduction
A 40-year-old man presented with basilar artery stroke. Six years previously he had a right supraclavicular desmoid tumour excised, which was closely related to the subclavian artery and T1 nerve root. At that time he was treated with postoperative radiotherapy.
CT angiogram and catheter angiography (Fig. 1) showed a false aneurysm 23
mm×22mm at the origin of the right vertebral artery and an embolus in the basilar artery. Basilar artery thrombolysis was performed with tPA and the patient made a good neurological recovery. To prevent further stroke a definitive procedure to exclude the pseudoaneurysm was required.
Figure 1
Right subclavian angiogram demonstrates the false aneurysm at the origin of the right vertebral artery.
2. Report
The patient had a four vessel cerebral angiogram (Fig. 2a,b) which revealed a hypoplastic left vertebral artery arising from the aortic arch. The patient underwent right common carotid to right vertebral artery bypass using reversed saphenous vein graft. Due to scarring and vessel friability the aneurysm was not dissected out nor opened. Considering the patient had an embolic stroke it was presumed that thrombus existed in the aneurysm. The right vertebral artery was ligated distal to the aneurysm and the bypass constructed distal to this. General anaesthesia was used with thiopentone at the time of cross clamp with a total clamp time of 24min. Active cooling was not used although the patient was allowed to cool passively. Intraoperative shunting was not possible. The carotid anastomosis was performed first and then flow was restored up the right carotid system before the vertebral anastomosis was performed. The procedure itself was difficult due to the desmoid tumour excision six years previously having left scarred and fibrosed tissues, as had the radiation therapy.
Figure 2
(a) Angiogram showing hypoplastic left vertebral artery arising from the aortic arch (arrow). (b) Left vertebral artery angiogram.
Postoperatively the patient had no signs or symptoms of a cerebral ischaemic event, but awoke with a right sided Horner's syndrome. A further angiogram was performed several days later with a view to inserting a covered stent into the subclavian artery across the vertebral artery origin to completely exclude the pseudoaneurysm from circulation, however the false aneurysm had already thrombosed and we felt that the stent was not required (Fig. 3).
Figure 3
Postoperative angiogram revealing patent bypass and thrombosed aneurysm.
At six months follow up the patient has remained asymptomatic with no further embolic events.
3. Discussion
True aneurysms of the extracranial vertebral artery are rare. Most vertebral artery aneurysms are pseudoaneurysms. Aetiology of pseudoaneurysms include iatrogenic, trauma, infection, tumour infiltration and vasculitis. Whilst pseudoaneurysms caused by dissection may be reversible, the history of previous surgery and radiation therapy and the preoperative imaging were not consistent with dissection. The natural history of these lesions is not well known. Some may rupture while some may spontaneously thrombose. Considering his risk of further stroke, the decision was made to exclude the aneurysm.
The issues raised by this case were 1) whether ligation and bypass or occlusion of the vertebral artery using coiling or stenting would be the optimal method of aneurysm exclusion in the presence of a hypoplastic left vertebral artery and 2) the optimal anaesthetic technique to provide intraoperative neuroprotection. The patient was at high risk of intra/postoperative stroke. Several options were considered including coiling, trial balloon occlusion and the use of intraoperative shunt.
Endovascular treatment of aneurysms is becoming popular with the advantages of being less invasive than conventional surgery and shorter hospital stays. However in this case a covered stent in the subclavian artery to exclude the right vertebral artery was considered high risk of a posterior circulation stroke because the contralateral vertebral artery was hypoplastic. Balloon occlusion of the right vertebral artery to assess the adequacy of flow from the contralateral vertebral was considered too high risk due to the risk of embolisation from the aneurysm. Stenting of the vertebral artery itself was not anatomically possible.
Coiling of the pseudoaneurysm and adjacent portion of the vertebral artery was considered too dangerous due to the hypoplastic contralateral vertebral artery. An intraoperative shunt was not possible due to limited access at surgery. Interestingly, a review of 144 cases of traumatic vertebral artery aneurysm by Schittek concluded that aneurysms involving V1 are most safely treated surgically rather than endovascularly.1
Anaesthetic considerations were needed due to clamping of the dominant vertebral artery during bypass. Options included deep hypothermic circulatory arrest and use of neuroprotective anaesthetic agents. Active cooling of patients to 33° was not shown to improve neurological outcome in intracranial aneurysm surgery in a prospective study on 1000 patients.2 Barbiturates have been shown to decrease cerebral oxygen consumption, and have successfully been used for neuroprotection.3 Less evidence exists for etomidate, propofol and ketamine as neuroprotective agents.4
To our knowledge this is the first report of a vertebral to carotid bypass graft for vertebral artery aneurysm with a hypoplastic contralateral vertebral. Kao et al5 reported a large vertebral artery aneurysm with absent contralateral vertebral artery however no procedure was performed. Due to the high complexity of surgery in this anatomical region, endovascular treatments of extracranial aneurysms are becoming more popular, however cases such as this one are a reminder that surgery still plays an important role in the management of vertebral aneurysmal disease.
Conflict of Interest
None declared.
Funding
None declared.
References
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- . Mild intraoperative hypothermia during surgery for intracranial aneurysm. N Engl J Med. 2005 Jan;352(2):135–145
- . Temporary occlusion of the middle cerebral artery in intracranial aneurysm surgery: time limitation and advantage of brain protection. J Neurosurg. 1997 Dec;87(6):817–824
- . Intravenous agents and intraoperative neuroprotection beyond barbiturates. Crit Care Clin. 1997 Jan;13(1):185–189
- . Large extracranial vertebral aneurysm with absent contralateral vertebral artery. Tex Heart Inst J. 2003;30(2):134–136
PII: S1533-3167(09)00006-5
doi:10.1016/j.ejvsextra.2009.02.003
© 2009 European Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
Refers to article:
- Carotid-Vertebral Artery Bypass for Symptomatic Vertebral Artery Pseudoaneurysm , 13 April 2009
