title: Correlation of xenon-enhanced computed tomography-defined cerebral blood flow reactivity and collateral flow patterns.
abstract: OBJECTIVE
  A chronic compromise of cerebral hemodynamics has been shown to identify a group of patients at an increased risk for stroke. Because a "steal phenomenon" induced by a vasodilatory challenge has characterized the group at greatest risk, it was hypothesized that these individuals would also have a severe compromise of primary collaterals and an increased dependence on leptomeningeal collaterals.
  
  
  METHODS
  Twenty-three patients with symptomatic cerebrovascular disease underwent angiography and xenon-enhanced computed tomographic cerebral blood flow studies before and after 1 g IV acetazolamide within 6 months of each other. Cerebral blood flow vasoreactivity was classified by whether cerebral blood flow increased (> 5%) or was unchanged (+/- 5%) (group 1) or fell by > 5% (group 2) in any vascular territory. Angiographic collateralization was classified into four types: normal (type 1), willisian (type 2), ophthalmic (type 3), and leptomeningeal (type 4).
  
  
  RESULTS
  Twenty percent (2/10) of group 1 patients and 69% (9/13) of group 2 patients (P = .0009) had leptomeningeal collaterals.
  
  
  CONCLUSIONS
  A negative flow reactivity is significantly associated with a dependence on leptomeningeal collaterals and implies a state of maximal hemodynamic compromise.
authors.affiliation: Department of Neurological Surgery, University of Pittsburgh, PA, School of Medicine.
authors.forename: H A
authors.initials: HA
authors.lastname: Smith
authors.forename: J
authors.initials: J
authors.lastname: Thompson-Dobkin
authors.forename: H
authors.initials: H
authors.lastname: Yonas
authors.forename: E
authors.initials: E
authors.lastname: Flint
mesh_terms: D000086:Acetazolamide; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000098:blood supply*; D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D002533:Cerebral Angiography; D002536:Cerebral Arteries / Q000187:drug effects / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002546:Ischemic Attack, Transient / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow / Q000187:drug effects; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014980:Xenon Radioisotopes
chemical_list: D014980:Xenon Radioisotopes; D000086:Acetazolamide