• 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:
  • 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)
Vertebrobasilar territory

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
Extracranial anastomoses in vertebral artery occlusion
Stenosis of the right subclavian artery, occlusion the left subclavian artery, occlusion of V0 segments bilaterally. Collateral circulation comes from the thyrocervical trunk

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
  • 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


  • 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
Stenosis of the left subclavian artery (CTA)
Subclavian artery stenosis on CTA
Occlusion of the brachiocephalic trunk on CTA

Digital subtraction angiography (DSA)

  • completely replaced by non-invasive methods in the diagnostic evaluation
  • most commonly performed only as a part of the intervention
Stenosis in the V0 segment of vertebral artery on DSA
Vertebral steal on DSA. Green arrow shows retrograde filling of vertebral artery and subclavian artery


Acute posterior circulation stroke

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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Vertebrobasilar steno-occlusive disease
link: https://www.stroke-manual.com/vertebrobasilar-steno-occlusive-disease/