Orthostatic intolerance: Different abnormalities in the neural sympathetic response to a gravitational stimulus

Raffaello Furlan, Renata Magatelli, Laura Palazzolo, Alexandra Rimoldi, Simona Colombo, Alberto Porta

Research output: Contribution to journalArticlepeer-review


In this paper we shall focus on the different abnormalities in the neural sympathetic response to a gravitational stimulus, characterising syndromes with symptoms of orthostatic intolerance.In Vaso-vagal Syncope, an increase or a reduction of cardiac and vascular sympathetic modulation have been described in occasional and habitual fainters, respectively. Pure Autonomic Failure (PAF) is characterized by a global cardiovascular denervation. Accordingly, the spectral markers of cardiac and vascular sympathetic modulation are absent or reduced. However, a concomitant vagal diminished activity is present. In Chronic Orthostatic Intolerance (COI), the most common form of dysautonomia in young female, an abnormal regional distribution of sympathetic discharge has been hypothesized during standing. Indeed, an overall increased sympathetic activity is present in recumbent position; during tilt a blunted vascular sympathetic discharge, with a concomitant exaggerated cardiac sympathetic modulation, is evident. Baroreflex Failure is a syndrome that may result from neck surgery or irradiation due to different forms of regional cancer. It is characterized by a volatility of blood pressure and heart rate, without habitual orthostatic hypotension. In the present paper, we describe a case of Baroreflex Failure with marked orthostatic hypotension in spite of a huge muscle sympathetic nerve activity (MSNA) and high levels of plasma cathecolamines. The most relevant finding was the absence of any coordinate rythmicity in blood pressure, heart rate and MSNA, both at rest and during tilt, particularly in the frequency band likely to be related with sympathetic modulation, i.e. at 0.1 Hz. We hypothesize that the absence of 0.1 Hz spontaneous fluctuations might play a role in sustaining orthostatic hypotension.

Original languageEnglish
Pages (from-to)83-88
Number of pages6
JournalAutonomic Neuroscience: Basic and Clinical
Issue number1-2
Publication statusPublished - Jul 20 2001


  • Baroreflex Failure
  • Muscle sympathetic nerve activity (MSNA)
  • Orthostatic intolerance
  • Sympathetic nervous system
  • Tilt test
  • Vaso-vagal Syncope

ASJC Scopus subject areas

  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Endocrine and Autonomic Systems


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