2026 Workshop Handout Bundle-W02B- Autonomic Testing

W02B- Autonomic Testing - Chawla

Pdf Summary

The workshop reviews practical autonomic testing and how to incorporate it into electrodiagnostic (EDX) practice. Autonomic disorders can affect involuntary functions including heart rate, blood pressure, temperature regulation, sweating, and bowel and bladder function. The clinical cases illustrate possible diabetic autonomic and small-fiber neuropathy, including burning feet, erectile dysfunction, and severe orthostatic hypotension.

Three testing approaches are emphasized:

- <strong>QSART</strong> assesses postganglionic sudomotor function by stimulating sweat-gland nerves with acetylcholine and measuring sweat output. It is highly sensitive, but samples only a small skin area, so a normal result does not exclude small-fiber neuropathy. Abnormal results can also occur with generalized dysautonomia, complex regional pain syndrome, skin disorders, and anticholinergic medication use. Results vary with age and sex.
- <strong>Heart-rate response to deep breathing (HRDB)</strong> is the most sensitive test of cardiovagal parasympathetic function. Heart rate normally rises during inspiration and falls during expiration; the difference across repeated breathing cycles is measured and interpreted in relation to age.
- <strong>The Valsalva maneuver</strong> evaluates cardiovascular autonomic reflexes. The patient sustains an open-glottis strain at 40 mmHg for 15 seconds while heart rate and blood pressure are monitored. The heart-rate ratio compares responses during phases II and IV. Blood-pressure patterns also help identify adrenergic failure, such as absent recovery in late phase II or an absent phase-IV overshoot. The maneuver has contraindications, including proliferative retinopathy, malignant hypertension, and cerebral aneurysm.

The presentation explains the physiological pathways underlying these responses and outlines test procedures, recording sites, and interpretation. Together, these basic autonomic studies can help identify and characterize autonomic dysfunction, while findings must be interpreted in clinical context.

Keywords

autonomic testing

electrodiagnostic practice

QSART

heart-rate response to deep breathing

Valsalva maneuver

small-fiber neuropathy

diabetic autonomic neuropathy

sudomotor function

cardiovagal function

orthostatic hypotension