ISCHEMIC STROKE / PREVENTION

Vertebrobasilar steno-occlusive disease

Created 06/02/2023, last revision 07/09/2023

the vertebrobasilar (VB) system (also called posterior circulation) comprises the subclavian, vertebral, and basilar arteries and their branches; it supplies the cervical spinal cord, brainstem, cerebellum, thalamus, and occipital lobes → anatomy of cerebral arteries

posterior circulation is frequently affected by atherosclerosis (AS), although less often than the anterior circulation
- incidence ~ 20-40% of all cerebrovascular disease patients
- atherosclerosis predominantly affects the origin of the vertebral arteries
in addition to atherosclerosis, other conditions may affect perfusion:
- hypoplasia or aplasia (may become relevant if another pathology occurs)
- variations in the arterial course (kinking, coiling) or origin
- mechanical oppression in the vertebral foramen (Bow hunter’s syndrome)
- subclavian (vertebral) steal syndrome
- dissection (typically in the V3 segment)
the most common mechanisms of posterior circulation stroke/TIA include:
- thromboembolism (resulting from plaque, dissection, or cardioembolism)
- hypoperfusion (caused by severe stenosis of various etiologies)
- vasospasm (less common)

Collateral circulation

compensatory collateral circulation may occur in the case of proximal stenosis or occlusion of the subclavian and vertebral arteries
- retrograde flow in the vertebral artery (from the contralateral VA, with or without steal phenomenon in the basilar artery)
- collaterals from the occipital artery and the thyrocervical trunk
- steal from a vertebral or mammary artery (with subclavian stenosis/occlusion)
- collateral retrograde flow from PCA (via PComA) to the basilar artery in case of its proximal occlusion

asymptomatic stenosis (very common)
- with/without steal phenomenon (asymptomatic flow alteration in a vertebral artery) on the ultrasound
weakened pulse and lower blood pressure in the affected limb may be present with significant subclavian artery stenosis
transient symptoms of hypoperfusion
posterior circulation stroke
- variable combination of symptoms from the brainstem, thalamus, cerebellum, and occipital and temporal lobes
- caused by hypoperfusion or thromboembolism
- transient symptoms (TIA) may precede the infarct

Content available only for logged-in subscribers (registration will be available soon)

CT angiography is preferred
CTA provides better visualization of the aortic arch and the origin of the vertebral arteries

recanalization therapy for all eligible patients → posterior circulation stroke

patients with symptomatic vertebral stenosis have a higher risk of recurrence than those with carotid stenosis [Flossmann, 2003]
- prospective studies found a 90-day risk of stroke after vertebrobasilar stroke/TIA of 9.6% in those with vertebrobasilar stenosis and 2.8% in those without, with the highest risk (13.9%) if the stenosis is intracranial (Gulli, 2009)
aggressive medical therapy (BMT) is crucial
there are no standardized indication criteria for intervention

Best medical treatment

(according to AHA/ASA 2021 1/A)

lifestyle modification
antiplatelet therapy
- usually aspirin 81-325 mg/d or clopidogrel 75 mg/d
hypolipidemic drugs (→ target lipid levels)
strict blood pressure control (adjust target value according to the degree of stenosis and collaterals status)
address other vascular risk factors
- smoking, obesity, diabetes, etc.

intervention may be suggested for patients with recurrent stroke/TIA despite receiving “best medical therapy”; the benefit is unknown (AHA/ASA 2021 2b/B-R)
indications for intervention include:
- thromboembolism – stenosis > 50% + more likely cause has been excluded
- hypoperfusion – stenosis > 70% + contralateral or multiple carotid artery lesions

Angioplasty/stenting

robust randomized data demonstrating the superior efficacy of extracranial vertebral angioplasty over conservative management are lacking
- smaller cohorts show the safety and efficacy of vertebral angioplasty (periprocedural complications 0-3%, success rates up to 94-98%)
- restenosis occurs in up to 43% of cases, with a maximum occurrence within 12 months after the procedure (though mostly asymptomatic)
relatively good results have also been reported for angioplasty of intracranial segments (V4, BA) [He, 2013]
- high risk of complication should lead to extreme caution
in general, angioplasty is considered for stenoses > 50% when aggressive medical therapy fails; benefit is uncertain (AHA/ASA 2021 2b/B-R)

Surgery

vertebral endarterectomy, vertebral transposition, etc., may be considered when aggressive medical therapy fails, but the benefit is unknown (AHA/ASA 2021 2b/C-EO)
procedures are associated with complications
no hard data comparing surgery and angioplasty

Subclavian bypass

intervention is generally not recommended in asymptomatic patients (AHA/ASA 2011 III/C)
- except for patients in whom the internal mammary artery is planned to be used for myocardial revascularization (cardiac steal) (AHA/ASA 2011 IIa/C)
procedures are indicated mainly in symptomatic patients despite BMT
- posterior circulation TIA/stroke
- upper extremity claudications
bypass surgery may be offered to symptomatic patients with low perioperative risk if angioplasty is not an option (AHA/ASA 2011 IIa/B)
- carotid-subclavian bypass
- aorta-subclavian bypass

Premedication and periprocedural monitoring are the same as for carotid angioplasty