title: TCD study of hemodynamic changes in PCA response to photic stimulation.
abstract: OBJECTIVE
  During visual stimulation, the elevated metabolism rate will couple with increase of blood flow velocity(BFV) in posterior cerebral artery(PCA). This study with TCD was aimed to investigate whether the coupling might change according to the different vasoneuronal conditions.
  
  
  METHODS
  Ninety-nine volunteers including 24 hypertension(HT) patients and 2 patients suffering from both HT and diabetes mellitus (DM) were enrolled in this trial. BFV and pulse indexes(PI) in P2 segments of PCA on both sides were monitored during visual stimulation.
  
  
  RESULTS
  In all subjects, Mean BFV increased and PI went down in response to visual stimulation. The percentages of changes (deltaV and deltaP) of both mean BFV and PI were larger in young group( < 55 years old) than in old one(> or = 55 years old). There was significant positive correlation between deltaV and deltaP. Multivariated regression analysis did not show HT and DM, but age related to deltaV(deltaP). We did not find significant difference of deltaV(deltaP) between left and right sides.
  
  
  CONCLUSIONS
  Blood flow velocity in PCA P2 segment increased due to decreased cerebrovascular resistance during visual stimulation and the response weakened with aging of the patient.
authors.affiliation: Department of Neurology, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.
authors.forename: Xu-Ning
authors.initials: XN
authors.lastname: Zheng
authors.forename: Xiong-Chao
authors.initials: XC
authors.lastname: Zhu
authors.forename: Qiu-Fang
authors.initials: QF
authors.lastname: Xu
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Huang
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002560:Cerebrovascular Circulation; D048909:Diabetes Complications; D003920:Diabetes Mellitus / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D020769:Posterior Cerebral Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D013223:Statistics as Topic; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*