Cerebral Revascularization After the Carotid Occlusion Surgery Study

What Candidates Remain, and Can We Do Better?

Timothy G. White, MD; Hussam Abou-Al-Shaar, MD; Jung Park, MD, PhD; Jeffrey Katz, MD; David J. Langer, MD; Amir R. Dehdashti, MD


Neurosurg Focus. 2019;46(2) 

In This Article

Abstract and Introduction


Objective: Cerebral revascularization for carotid occlusion was previously a mainstay procedure for the cerebrovascular neurosurgeon. However, the 1985 extracranial-intracranial bypass trial and subsequently the Carotid Occlusion Surgery Study (COSS) provided level 1 evidence via randomized controlled trials against bypass for symptomatic atherosclerotic carotid occlusion disease. However, in a small number of patients optimal medical therapy fails, and some patients with flow-limiting stenosis develop a perfusion-dependent neurological examination. Therefore it is necessary to further stratify patients by risk to determine who may most benefit from this intervention as well as to determine perioperative morbidity in this high-risk patient population.

Methods: A retrospective review was performed of all revascularization procedures done for symptomatic atherosclerotic cerebrovascular steno-occlusive disease. All patients undergoing revascularization after the publication of the COSS in 2011 were included. Perioperative morbidity and mortality were assessed as the primary outcome to determine safety of revascularization in this high-risk population. All patients had documented hypoperfusion on hemodynamic imaging.

Results: At total of 35 revascularization procedures were included in this review. The most common indication was for patients with recurrent strokes, who were receiving optimal medical therapy and who suffered from cerebrovascular steno-occlusion. At 30 days only 3 perioperative ischemic events were observed, 2 of which led to no long-term neurological deficit. Immediate graft patency was good, at 94%. Long term, no further strokes or ischemic events were observed, and graft patency remained high at 95%. There were no factors associated with perioperative ischemic events in the variables that were recorded.

Conclusions: Cerebral revascularization may be done safely at high-volume cerebrovascular centers in high-risk patients in whom optimal medical therapy has failed. Further research must be done to develop an improved methodology of risk stratification for patients with symptomatic atherosclerotic cerebrovascular steno-occlusive disease to determine which patients may benefit from intervention. Given the high risk of recurrent stroke in certain patients, and the fact that patients fail medical therapy, surgical revascularization may provide the best method to ensure good long-term outcomes with manageable up-front risks.


INDICATIONS for cerebral revascularization have decreased over the last decade. Its indications fall into 2 main categories: 1) flow augmentation in the setting of ischemia, and 2) flow replacement in the setting of complex cerebral aneurysms or tumors. Flow augmentation has been well studied, with the recent publications of the Carotid Occlusion Surgery Study (COSS), the Japanese Adult Moyamoya Trial, and the Japan Extracranial-Intracranial Bypass Trial (JET).[8–10] Flow augmentation may be done in the setting of moyamoya disease, a rare steno-occlusive disease of the intracranial vasculature, or for symptomatic cerebral atherosclerotic stenosis and occlusion. However, historical and recent randomized clinical trials have whittled down the indications for bypass in the setting of cerebrovascular atherosclerotic steno-occlusive disease.

The first trial, published in the New England Journal of Medicine in 1985, showed no benefit for cerebral revascularization in patients with symptomatic nonmoyamoya vasculopathy; however, it failed to stratify patients by risk in order to determine which would receive the greatest benefit from intervention.[1] Subsequently, the St. Louis Carotid Occlusion Study (STLCOS) was able to identify patients at the highest risk for recurrent stroke in the setting of cerebrovascular stenosis and occlusion by using PET oxygen extraction fraction (OEF).[3,5] The COSS was then designed on this premise.[7] In order to determine whether patients with symptomatic cerebral atherosclerotic stenosis and occlusion who are at the highest risk of recurrent stroke would benefit from revascularization, patients in the COSS underwent PET OEF in order to stratify them by risk. They were then randomized to best medical therapy versus surgical revascularization. Despite numerous criticisms, the ultimate outcome showed that surgical revascularization provided no benefit over best medical therapy, mostly due to the impressive natural history of medical therapy and the perioperative surgical risk associated with revascularization.[6,11] That being said, more recent studies still demonstrate that misery perfusion is a predictor of stroke risk in patients with symptomatic atherosclerotic cerebrovascular steno-occlusive disease, even with newer optimal medical management.[13]

A small group of patients develop ischemic symptoms and symptomatic hypoperfusion (limb shaking and/or crescendo transient ischemic attacks [TIAs] or orthostatic hypoperfusion) even on optimal medical therapy, due to severe hemodynamic impairment. This group of patients has not been well studied by prior trials. There is little literature on their clinical syndrome and subsequent outcome and surgical risk after undergoing revascularization. The purpose of this study was to identify this group of patients and discuss their surgical outcomes in a single institution's series.