Failure of cerebral hemodynamic selection in general or of specific positron emission tomography methodology?: Carotid Occlusion Surgery Study (COSS)

Stroke. 2011 Dec;42(12):3637-9. doi: 10.1161/STROKEAHA.111.627745. Epub 2011 Sep 29.


Background and purpose: The Carotid Occlusion Surgery Study (COSS) was an improvement over the Extracranial-Intracranial Bypass Study, which did not utilize physiological selection. To assess possible reasons for early closure of the COSS trial, we reviewed COSS methods used to identify high-risk patients and compared results with separate quantitative data.

Methods: Increased oxygen extraction fraction (OEF) by positron emission tomography is a gold standard for ischemia, but the specific thresholds and equivalency of the semiquantitative OEF ratio utilized in COSS and quantitative OEF are at issue.

Results: The semiquantitative hemispheric OEF ratio used in COSS did not identify the same group of patients as did quantitative OEF using a threshold of 50%.

Conclusions: The failure of COSS is likely caused by a failure of the semiquantitative, hemispheric OEF ratio method rather than by the selection for bypass based on hemodynamic compromise.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Brain Ischemia / diagnostic imaging
  • Brain Ischemia / etiology*
  • Brain Ischemia / physiopathology
  • Carotid Stenosis / complications
  • Carotid Stenosis / diagnostic imaging
  • Carotid Stenosis / physiopathology
  • Carotid Stenosis / therapy*
  • Humans
  • Positron-Emission Tomography
  • Randomized Controlled Trials as Topic
  • Risk Factors
  • Stroke / diagnostic imaging
  • Stroke / etiology*
  • Stroke / physiopathology