ISCHEMIC STROKE / PREVENTION

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)
• 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)

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

Management