title: Supine-to-standing transcranial Doppler test in patients with multiple system atrophy.
abstract: BACKGROUND
  Supine-to-standing test, a transcranial Doppler (TCD) based technique, has been recently developed to evaluate cardiovascular dysautonomia. We explored the value of supine-to-standing TCD test in predicting the course of multiple system atrophy (MSA) with orthostatic hypotension (OH).
  
  
  METHODS
  By monitoring the signals of middle cerebral artery during supine-to-standing posture changes, the trend curves of cerebral blood flow velocities, pulsatility index and resistance index were obtained from 38 MSA patients with OH and 31 healthy subjects. The correlation between TCD findings and the clinical outcome of the patients, which was determined by follow-up structured phone interview, was analyzed. Adverse outcome was defined if a patient died, was in bed-ridden state or had recurrent syncope (>1 per month).
  
  
  RESULTS
  Two characteristic TCD findings were revealed in the MSA patients but not in the controls, i.e. a blunted cerebral blood flow velocity rebound after standing and/or sustained higher pulsatility index upon standing than supine baseline. Structured phone interview was completed in 31 of the 38 patients (mean follow-up time, 20 ± 11 months). While no subject had recurrent syncope before enrollment, 12 patients developed an adverse outcome during follow-up. The coexistence of two characteristic TCD findings predicted adverse outcomes with positive predictive value 66.7% and negative predictive value 87.5%.
  
  
  CONCLUSIONS
  Supine-to-standing TCD test is valuable in predicting the course of MSA with OH at early stage. We hypothesize baroreflex failure effects and paradoxical cerebral vasoconstriction in response to OH may account for the TCD findings in MSA patients.
authors: Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Shuaifuyuan 1, Beijing 1000730, China. xuwhpumch@yahoo.com.cn
authors: Wei-Hai
authors: WH
authors: Xu
authors: Han
authors: H
authors: Wang
authors: Ying-Huan
authors: YH
authors: Hu
authors: Bo
authors: B
authors: Wang
authors: Jie
authors: J
authors: Chen
authors: Shan
authors: S
authors: Gao
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis* / Q000503:physiopathology; D011187:Posture / Q000502:physiology*; D016683:Supine Position / Q000502:physiology*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*