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Brain Bypass Surgery

What is brain bypass surgery?

Brain bypass, or EC-IC bypass, is a surgical procedure used to reroute blood around a blocked blood vessel in the brain to restore blood flow. During a brain bypass, a small hole in the skull is made to expose the area of the brain that needs to be treated. The surgeon then takes a healthy blood vessel from outside the brain (usually from the scalp) and connects it to a blood vessel inside the brain to reroute blood around a blocked or narrowed artery, restoring blood flow to the brain. A brain bypass can also take a vein from the arm or leg and use it to direct blood around a blockage. The basics of the brain bypass surgery are similar to coronary artery bypass graft (CABG) surgery to get around blockages in the arteries that supply blood to the heart.

Who might undergo brain bypass surgery?

In 1985, a large international study found that brain bypass surgery had no clear-cut benefits for most stroke patients, compared to standard treatment with medication.1 Since then the procedure has not been performed very often, although it may still be used in a select group of high-risk patients with large aneurysms or other major blockages in the brain.2-4

Brain bypass is not recommended for most people who have had a blocked-vessel (ischemic) stroke.5, 6 However, there are studies underway using newer types of brain imaging tests to try to identify high-risk patients with narrowing in the internal carotid artery who may benefit from the surgery.6-8

A brain bypass may also be used if you have aneurysms that can't be treated with other surgeries (see treatments for bleeding stroke) alone or if you have a condition called moyamoya disease, a blockage at the base of the skull of arteries that supply blood to the brain.3, 4

What are the risks associated with brain bypass?

As with any surgical procedure, brain bypass has risks. Serious complications occur in about 1% to 4% of patients.1, 9 Possible complications include stroke, TIA, bleeding in the brain, infection, loss of vision and even death.


  1. Failure of extracranial-intracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international randomized trial. The EC/IC Bypass Study Group. N Engl J Med. Nov 7 1985;313(19):1191-1200.
  2. Tummala RP, Chu RM, Nussbaum ES. Extracranial-intracranial bypass for symptomatic occlusive cerebrovascular disease not amenable to carotid endarterectomy. Neurosurg Focus. Mar 15 2003;14(3):e8.
  3. O'Shaughnessy BA, Salehi SA, Mindea SA, Batjer HH. Selective cerebral revascularization as an adjunct in the treatment of giant anterior circulation aneurysms. Neurosurg Focus. Mar 15 2003;14(3):e4.
  4. Reis CV, Safavi-Abbasi S, Zabramski JM, Gusmao SN, Spetzler RF, Preul MC. The history of neurosurgical procedures for moyamoya disease. Neurosurg Focus. 2006;20(6):E7.
  5. Adams HP, Jr., del Zoppo G, Alberts MJ, et al. Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists. Stroke. May 2007;38(5):1655-1711.
  6. Sacco RL, Adams R, Albers G, et al. Guidelines for prevention of stroke in patients with ischemic stroke or transient ischemic attack: a statement for healthcare professionals from the American Heart Association/American Stroke Association Council on Stroke: co-sponsored by the Council on Cardiovascular Radiology and Intervention: the American Academy of Neurology affirms the value of this guideline. Stroke. Feb 2006;37(2):577-617.
  7. Grubb RL, Jr., Powers WJ, Derdeyn CP, Adams HP, Jr., Clarke WR. The Carotid Occlusion Surgery Study. Neurosurg Focus. Mar 15 2003;14(3):e9.
  8. Carotid Occlusion Surgery Study (COSS). ClinicalTrials.gov [December 17, 2007; http://clinicaltrials.gov/ct2/show/NCT00029146?term=COSS&rank=2. Accessed March 3, 2008.
  9. Mendelowitsch A, Taussky P, Rem JA, Gratzl O. Clinical outcome of standard extracranial-intracranial bypass surgery in patients with symptomatic atherosclerotic occlusion of the internal carotid artery. Acta Neurochir (Wien). Feb 2004;146(2):95-101.


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