title: Basilar and middle cerebral artery reserve: a comparative study using transcranial Doppler and breath-holding techniques.
abstract: OBJECTIVE
  A 1997 report suggests that the posterior circulation of the normal brain has diminished vasoreactivity compared with the anterior circulation. To further study this, we quantified and compared the vasodilatory capacities of the middle cerebral (MCA) and basilar artery (BA) territories in response to changes in PaCO(2), as indices of respective cerebrovascular reserve (CVR). If posterior circulation CVR is indeed physiologically lower than that of the MCA, it might indicate a greater risk of low-flow ischemia distal to basilar obstructive cerebrovascular lesions and provide a rationale for earlier treatment of such lesions with interventional techniques. We also wished to establish normal baseline CVR values for the posterior circulation.
  
  
  METHODS
  Twelve patients with signs and/or symptoms suggestive of posterior circulation disease but without flow-limiting obstructive changes and 11 normal controls were entered into the study. With the use of transcranial Doppler techniques, alterations in blood flow velocity in response to sequential breath-holding trials of varying duration were simultaneously monitored in both MCAs and the BA. CVR was measured as the percent velocity increase (during breath-holding) from resting baseline values.
  
  
  RESULTS
  No significant differences were found in CVR between the MCA and BA territories in or between patients and controls.
  
  
  CONCLUSIONS
  Our study suggests that the anterior and posterior circulations have similar reserve capacities in individuals without flow-limiting cerebrovascular obstructive lesions and that the BA territory, relative to the MCA territory, is not at increased risk for low-flow stroke on the basis of limited reserve potential.
authors.affiliation: Department of Neurology, Massachusetts General Hospital, and the Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Barrett
authors.forename: R H
authors.initials: RH
authors.lastname: Ackerman
authors.forename: G
authors.initials: G
authors.lastname: Gahn
authors.forename: J M
authors.initials: JM
authors.lastname: Romero
authors.forename: M
authors.initials: M
authors.lastname: Candia
mesh_terms: D000328:Adult; D000368:Aged; D001488:Basilar Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D007040:Hypoventilation / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012016:Reference Values; D018570:Risk Assessment; D017585:Ultrasonography, Doppler, Transcranial; D014664:Vasodilation