title: Dynamic cerebrovascular regulation in patients with autonomic dysfunction: a transcranial Doppler study.
abstract: BACKGROUND
  Regulation of cerebral blood flow during orthostatic stress has been a major research interest. The purpose of this study was to scan healthy volunteers and patients with orthostatic dizziness and autonomic dysfunction for differences in cerebral hemodynamic patterns during orthostasis.
  
  
  METHODS
  Thirteen patients with orthostatic dizziness and autonomic dysfunction and 9 healthy volunteers were recruited for monitoring of variations in intracranial hemodynamics with transcranial Doppler ultrasound during a 30-minute head-up tilt. Heart rate and blood pressure were monitored with surface electrocardiography and cuff sphygmomanometer, respectively. Cerebral blood flow velocity was continuously monitored using transcranial Doppler ultrasonography.
  
  
  RESULTS
  The baseline mean cerebral blood flow velocity was significantly lower in the patient group (p < 0.05). After tilting up, the extent of immediate decreases in systolic blood pressure and in the mean blood flow velocity were significantly more in the patients (p < 0.05). However, the mean blood flow velocity remained significantly more retarded for up to 90 seconds after the initial drop in the patient group, while the blood pressure showed no significant difference between the patients and controls.
  
  
  CONCLUSIONS
  Impaired dynamic cerebrovascular regulation can be documented as a delayed recovery of cerebral blood flow velocity upon orthostatic challenges, which may help verify the status of cerebrovascular regulation in patients with autonomic dysfunction.
authors.affiliation: Department of Neurology, Kaohsiung Medical University, Kaohsiung, Taiwan, ROC.
authors.forename: A-Ching
authors.initials: AC
authors.lastname: Chao
authors.forename: Han-Hwa
authors.initials: HH
authors.lastname: Hu
authors.forename: Kwong-Kan
authors.initials: KK
authors.lastname: Liao
authors.forename: Chang-Ming
authors.initials: CM
authors.lastname: Chern
mesh_terms: D000328:Adult; D000368:Aged; D001342:Autonomic Nervous System Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001794:Blood Pressure; D002560:Cerebrovascular Circulation; D004244:Dizziness / Q000503:physiopathology; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D017585:Ultrasonography, Doppler, Transcranial