title: Transcranial Doppler sonography during head up tilt suggests preserved central sympathetic activation in familial dysautonomia.
abstract: OBJECTIVE
  Cerebral autoregulation was assessed by transcranial Doppler sonography in 10 patients with familial dysautonomia and 10 age matched controls.
  
  
  METHODS
  Blood pressure, heart rate, and middle cerebral artery blood flow velocity (CBFV) were simultaneously recorded when supine and during 180 seconds of head up tilt. Cerebrovascular resistance (CVR) was calculated from CBFV and mean blood pressure was adjusted to brain level.
  
  
  RESULTS
  In the controls, mean blood pressure remained stable during tilt, but heart rate increased significantly. In the patients with familial dysautonomia, mean (SD) blood pressure decreased by 15.0 (10.8)% (p < 0.05). Heart rate remained unchanged. In controls, systolic and mean CBFV decreased by 9.1 (4.7)% and 9.4 (7.0)%, respectively, while diastolic CBFV remained stable. In the patients, diastolic and mean CBFV decreased continuously by 32.1 (13.9)% and by 14.8 (31.4)%. Supine CVR was 28% higher in patients than in controls and decreased significantly less during head up tilt.
  
  
  CONCLUSIONS
  Tilt evokes orthostatic hypotension without compensatory tachycardia in patients with familial dysautonomia owing to decreased peripheral sympathetic innervation. High supine CVR values and relatively preserved CVR during tilt suggest preserved central sympathetic activation in familial dysautonomia, assuring adaptation of cerebrovascular autoregulation to chronic supine hypertension and orthostatic hypotension.
authors.affiliation: Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany. max.hilz@neuro.med.uni-erlangen.de
authors.forename: M J
authors.initials: MJ
authors.lastname: Hilz
authors.forename: F B
authors.initials: FB
authors.lastname: Axelrod
authors.forename: U
authors.initials: U
authors.lastname: Haertl
authors.forename: C M
authors.initials: CM
authors.lastname: Brown
authors.forename: B
authors.initials: B
authors.lastname: Stemper
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure; D002540:Cerebral Cortex / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000502:physiology; D002648:Child; D004402:Dysautonomia, Familial; D005260:Female; D006339:Heart Rate; D006706:Homeostasis; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D008297:Male; D012039:Regional Blood Flow; D018667:Tilt-Table Test; D018608:Ultrasonography, Doppler