Diagnosis

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