Who should take the ANS test?
EXAMPLES OF THE MANY SITUATIONS WHERE AUTONOMIC TESTING IS OF CLINICAL UTILITY INCLUDE
- Patients with syncope: Autonomic testing is necessary to differentiate neurally mediated syncope from neurogenic orthostatic hypotension and other causes of syncope.
- Patients with diabetes mellitus: All patients with diabetes are recommended to have autonomic testing (sudomotor, cardiovagal and adrenergic) at diagnosis (type 2 diabetes) or five years after diagnosis (type 1 diabetes). There is a high prevalence of cardiovascular autonomic neuropathy in the diabetic population. The relationship between autonomic dysfunction and cardiovascular risk has been well documented and is important to monitor for patients planning major surgical procedures or considering moderate to high intensity physical exercise. This is the reason that the ADA recommends autonomic testing for all patients with type 2 diabetes at the time of diagnosis, and all patients with type 1 diabetes five years after diagnosis. The increased perioperative mortality in cardiovascular autonomic neuropathy is linked to greater blood pressure instability and hypothermia. This information may prompt high‐risk patients to forgo an elective procedure or allow the anesthesiologist to prepare for potential hemodynamic changes, thereby reducing the risks of morbidity and mortality.
- Patients with orthostatic dizziness: Patients with recurrent dizziness when standing may have autonomic dysfunction, postural tachycardia syndrome, or other autonomic neuropathy that can be treated if a diagnosis is made. All autonomic tests (sudomotor, cardiovagal, and adrenergic) are appropriate to use in forming a differential diagnosis, defining the physiology of orthostatic intolerance in the individual patient, grading the severity of impairment, and directing appropriate therapy.
- Patients with disorders of sweating: Autonomic testing can provide a diagnosis which can lead to treatment of the underlying disorder and improvements in clinical outcomes. Patients found to have global anhidrosis may be at risk for heat exhaustion or heat stroke and can benefit from interventions to restore sweating, when a reversible cause is diagnosed, or otherwise from management strategies to avoid heat stress. Although sudomotor testing will provide specific information about the problem with sweating, cardiovagal, and adrenergic testing will narrow the differential diagnosis and are therefore integral parts of the autonomic test (i.e., does the patient have an autonomic ganglionopathy, an isolated autonomic neuropathy such as Ross syndrome, a peripheral neuropathy causing distal anhidrosis and proximal hyperhidrosis, how severe or anatomically widespread is the deficit, etc.).
- Patients with peripheral neuropathy from a number of different causes such as (but not limited to) amyloidosis, Fabry’s disease, Sjögren’s syndrome, and autoimmune neuropathies.