Vertebrobasilar Insufficiency



  • Vertebrobasilar (VB) vascular system feeds the posterior region of the brain, which includes the brainstem, cerebellum, and inner ear
  • 2 vertebral arteries (VA) derive from subclavian arteries and give rise to the anterior spinal artery and then join to form the basilar artery
  • Arteries supplying the brainstem and cerebellum originate from the VB system before it branches into the 2 posterior cerebral arteries (PCA), such that a wide variety of focal neurologic deficits arise from VB circulatory dysfunction
  • Vertebrobasilar insufficiency (VBI) results in inadequate perfusion of VB arterial circulation from thrombotic, embolic, or low-flow states


  • Mechanism:
    • Thrombosis:
      • VB ischemia due to underlying VB atherosclerosis and clot formation
    • Embolus:
      • VB ischemia due to embolization of clot from proximal location
    • Low-flow states:
      • Hypoperfusion of VB system from systemic (e.g., cardiogenic shock) or localized (e.g., subclavian steal) reduction in blood flow
    • Less common etiologies:
      • Fibromuscular dysplasia
      • Hypercoagulable states
  • Ischemic mechanisms causing VB insufficiency can herald and lead to VB territory infarcts
  • Severe episodes of VB hypoperfusion or loss of circulation can lead to:
    • “Locked-in” syndrome:
      • Quadriplegia (eyelid or eye movement only) with intact consciousness
    • “Top-of-basilar” syndrome:
      • Pontine and cerebellar dysfunction with diminished level of consciousness

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