diagnosis

Last reviewed 10/2023

The diagnosis of autonomic failure may be confirmed by the following test results:

  • cardiovascular reflexes:
    • postural hypotension or more than 20 mmHg
    • absence of sinus arrhythmia with deep breathing
    • no bradycardia with carotid sinus massage
    • no hypertension or tachycardia when stressed e.g. loud noise, immersion of hand in cold water, mental arithmetic
    • no hypertension following Valsalva:
      • patient forcibly exhales through a tube for 12 sec
      • normally the blood pressure increases after, this is absent in autonomic failure
    • plasma noradrenaline low and unchanged after 30 min standing or sitting
  • sweating:

    • þþ no sweating following 90 min at a body temperature 1 deg.C. above normal

    • pupillary responses:
      • pupil dilates after instillation of 1:1000 adrenaline