Which additional tests may be needed for the diagnosis of autonomic failure syndromes?

Updated: Oct 21, 2018
  • Author: Mohini Gurme, MD; Chief Editor: Selim R Benbadis, MD  more...
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Nerve conduction studies (NCS) and electromyography (EMG) are important to document any coexisting neuropathy or disorder of neuromuscular transmission.

Additional autonomic testing, such as sympathetic skin response, is available in some electrodiagnostic laboratories. Skin vasomotor responses and sweat testing are 2 highly specialized autonomic tests that can be performed in a few autonomic laboratories. Skin vasomotor responses may help distinguish PAF from MSA. Sweat testing, either with acetylcholine iontophoresis or thermoregulatory testing, may be helpful even if the patient does not complain specifically of sweating abnormalities.

GI motility can be evaluated in a number of ways, including an upper or lower GI series, cine videofluoroscopy, endoscopy, and gastric-emptying studies.

Bladder ultrasound and postvoiding residual volumes should be assessed in patients with urinary symptoms. Urodynamic studies and intravenous urography also may help to define the cause of urinary retention or incontinence.

Male impotence can be evaluated by using penile plethysmography and response to intracavernosal papaverine.

Measurement of levels of plasma noradrenalin with the patient supine may help distinguish central from peripheral autonomic failure. MSA patients, who have centrally mediated autonomic failure, have normal supine levels of noradrenalin.

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