ISCHEMIC STROKE / PREVENTION

Extracranial-intracranial bypass

Created 23/09/2022, last revision 24/12/2022

• ICA occlusion is responsible for ~15-25% of strokes
• ICA occlusion is associated with a 2-year stroke risk of about 10-15%
  • the risk is even higher in the presence of impaired VMR  [Vernieri, 1999]
• extracranial-intracranial (EC-IC) arterial bypass surgery was developed to prevent stroke by improving hemodynamics distal to the occluded artery
  • in patients with symptomatic atherosclerotic ICA occlusion
  • in patients who would not tolerate planned ICA ligation (for surgically inaccessible aneurysms, tumors, etc.) according to balloon test occlusion (BTO)
• studies have not demonstrated the effectiveness of EC-IC bypass compared to conservative therapy in secondary stroke prevention in patients with ICA occlusion; even if techniques assessing hemodynamic impairment are used (see the COSS trial from 2011)

• the theoretical indications are untreatable ICA stenosis/occlusion or MCA occlusion
• the most commonly performed procedures (using a graft from the radial artery or sphenoid):
  • bypass between the superficial temporal artery (STA) and one of the cortical MCA branches
  • ICA-MCA bypass
  • indirect anastomoses
    • this bypass is most commonly offered in patients with moyamoya

• theoretical can be offered in otherwise untreatable stenoses and occlusions of vertebral and basilar arteries
• usually, the connection between the occipital artery and PICA or SCA is established
  • it is possible to create a high-flow bypass using a graft from the saphenous vein