ISCHEMIC STROKE / PREVENTION
Vertebrobasilar steno-occlusive disease
Created 06/02/2023, last revision 06/02/2023
- the vertebrobasilar (VB) system (also called posterior circulation) consists of the subclavian, vertebral and basilar arteries and 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 patients with cerebrovascular disease
- predominantly affects the origin of the vertebral artery
- in addition to atherosclerosis, other conditions may affect perfusion:
- hypoplasia or aplasia
- 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 V3 segment)
- hypoplasia or aplasia
- the most common mechanisms of posterior circulation stroke/TIA are:
- thromboembolism (from plaque, dissection, cardioembolism)
- hypoperfusion (due to severe stenosis of various etiologies)
- vasospasm (less frequent)
- thromboembolism (from plaque, dissection, cardioembolism)
Collateral circulation
- proximal stenosis/occlusion of the subclavian and vertebral arteries may be compensated by collateral circulation:
- 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
Clinical presentation
- 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 hypoperfusion symptoms
- most often vertigo or drop attacks
- subclavian (vertebral) steal syndrome
- Bow-hunter’s syndrome
- posterior circulation TIA/stroke
- variable combination of symptoms from the brainstem, thalamus, cerebellum, and occipital and temporal lobes
- caused by hypoperfusion or thromboembolism or both
- transient symptoms (TIA) may precede the infarct
Diagnostic evaluation
Neurosonology
- first-line method – accurate, non-invasive, safe, widely available and inexpensive
- useful in combination with CTA is useful when the invasive procedure is planned
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CT/MR angiography
- CT angiography is preferred
Digital subtraction angiography (DSA)
- completely replaced by non-invasive methods in the diagnostic evaluation
- most commonly performed only as a part of the intervention
Management
Acute posterior circulation stroke
- recanalization therapy for all eligible patients
- medical therapy (see below) for the remainder
Stroke prevention
- patients with symptomatic vertebral stenosis have a higher risk of recurrence than patients with carotid stenosis [Flossmann, 2003]
- aggressive medical therapy is crucial
- there are no standardized indication criteria for intervention
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