# Autonomic Testing Protocols | Symptoms, Causes, Tests and Treatment | OSANG > The autonomic nervous system test protocol is a standard test system that comprehensively evaluates various effector functions of the autonomic nervous system, including… - Official page: https://osns.co.kr/en/encyclopedia/autonomic-testing-protocols - Organization: OSANG Neurosurgery ## Page content Diagnostic Tools ## Autonomic Testing Protocols Autonomic Testing Protocols The autonomic nervous system test protocol is a standardized test combination to systematically evaluate the function of the sympathetic and parasympathetic nervous systems, and is essential for objective diagnosis and severity classification of autonomic nervous system dysfunction. ## At a glance The autonomic nervous system test protocol is a standard test system that comprehensively evaluates various effector functions of the autonomic nervous system, including the cardiovascular system, sweating, and pupil response. The Ewing test battery is the classic standard and includes heart rate variability (HRV), Valsalva maneuver, orthostatic blood pressure test, orthostatic tilt test, and sweat function test. It is performed by combining at least three tests, and its sensitivity and specificity are higher than those of a single test. - 01Definition and Overview - 02Preparation before inspection - 03standard test battery - 04Interpretation of results - 05Limitations of the test ## Definition and Overview The autonomic testing protocol is a combination of standardized tests to evaluate the function of the sympathetic and parasympathetic nervous systems in an objective and reproducible manner. Since the autonomic nervous system controls a wide range of functions, including cardiovascular, sweating, digestion, and urogenital functions, it is difficult to determine the overall functional status through a single test. Therefore, a test battery that evaluates multiple effectors simultaneously is needed. ## Preparation before inspection ### Patient Preparation For accurate test results, the following must be observed: - Fasting for at least 3 hours before the test (water is allowed) - Avoid consuming caffeine, nicotine, or alcohol on the day of the test - Comfortable clothes, plenty of sleep - Maintain laboratory temperature between 22 and 24°C ### drug withdrawal Discontinue medications that affect the autonomic nervous system before an appropriate period of time, in consultation with your doctor. - Beta-blockers, alpha-blockers: more than 48 hours ago - Anticholinergics, antihistamines: more than 48 hours before - Tricyclic antidepressants, SSRIs: 5 to 7 days before (gradual reduction) - midodrine, fludrocortisone: more than 24 hours ago ## standard test battery ### 1. Cardiovascular parasympathetic function test #### Heart Rate Variability (HRV) Record the electrocardiogram at rest and analyze indicators in the time domain (RMSSD, pNN50) and frequency domain (LF, HF, LF/HF ratio). The HF (0.15~0.40 Hz) component reflects parasympathetic nerve activity, and the LF/HF ratio represents sympathetic-parasympathetic balance. #### Deep breathing test Heart rate fluctuations are measured while taking 6 deep breaths per minute. The expiratory-inspiratory heart rate difference (E:I ratio) is a sensitive indicator of parasympathetic function. There are normal standards for each age; more than 15 times/minute is considered normal, and less than 10 times/minute is considered abnormal. #### Valsalva maneuver While forced expiration is maintained for 15 seconds at a pressure of 40 mmHg, the four-phase response (phase I to IV) of heart rate and blood pressure is observed. Valsalva ratio (phase IV maximum heart rate/phase II minimum heart rate) reflects parasympathetic function, and a value of 1.21 or higher is normal. ### 2. Cardiovascular sympathetic function test #### Active standing blood pressure test Changes in blood pressure and heart rate are measured when standing from the supine position. Orthostatic hypotension is diagnosed when systolic blood pressure drops by more than 20 mmHg or diastolic blood pressure by more than 10 mmHg within 3 minutes of standing. #### Head-up tilt test Observe changes in blood pressure and heart rate for 20 to 45 minutes while passively maintaining a standing position of 60 to 70 degrees. It is essential in the differential diagnosis of vasovagal syncope, POTS, and orthostatic hypotension. #### Valsalva maneuver blood pressure response Analyze the four-stage response of blood pressure during the Valsalva maneuver. Failure of blood pressure recovery late in Phase II and loss of Phase IV overshoot suggest sympathetic dysfunction. ### 3. Sweating function test #### Quantitative axon reflex sweating test (QSART) Sweating is induced using acetylcholine iontophoresis, and the amount of sweating is quantitatively measured. It is performed in four areas: forearm, proximal lower extremity, distal lower extremity, and foot, and is useful for early diagnosis of small fiber neuropathy and autonomic neuropathy. #### Thermoregulatory sweat test (TST) After applying a sweating indicator (alizarin red powder) to the entire body, the room temperature is raised to increase body temperature by 1°C and the distribution of sweating is observed. Central-peripheral lesions are differentiated based on the pattern of anhidrosis area. ## Interpretation of results ### Composite Autonomic Severity Score (CASS) The Composite Autonomic Severity Score (CASS), developed by the Mayo Clinic, quantifies the severity of autonomic dysfunction with a score of 0 to 10 by adding three subscores: sweating (0 to 3 points), cardiovascular adrenaline (0 to 4 points), and cardiovascular choline (0 to 3 points). - 0 points: normal - 1 to 3 points: mild dysfunction - 4 to 6 points: moderate functional impairment - 7-10 points: severe functional impairment ### Clinical Interpretation Patterns - Parasympathetic dominance disorder: decreased deep breathing heart rate variability + decreased Valsalva ratio, normal orthostatic blood pressure → early stage of diabetic autonomic neuropathy - Widespread autonomic failure: decreased parasympathetic + sympathetic functions + orthostatic hypotension → multiple system atrophy, pure autonomic failure - Selective sympathetic dysfunction: sweating abnormalities + orthostatic hypotension, relative preservation of parasympathetic function → dopamine β-hydroxylase deficiency - POTS pattern: Increased heart rate by more than 30 bpm upon standing, no orthostatic hypotension, possibly accompanied by abnormal sweating. ## Limitations of the test Autonomic nerve test results are affected by age, gender, medication, water intake, laboratory environment, etc., so it should be performed under standardized conditions and normal values for each age should be applied. Additionally, abnormal test results do not necessarily indicate a specific disease and must be interpreted in conjunction with clinical findings. ## Frequently asked questions ### Q01What preparations are needed before undergoing an autonomic nerve test? Fast for at least 3 hours before the test, and avoid coffee, smoking, and alcohol. To obtain accurate results, medications that affect the autonomic nervous system (beta-blockers, anticholinergics, antihistamines, etc.) must be discontinued 48 hours to 1 week in advance in consultation with your doctor. ### Q02How long does the test take? The basic test battery (heart rate variability + Valsalva maneuver + standing test) takes about 30 to 45 minutes, and including the standing tilt test takes about 60 to 90 minutes. If a sweating function test (QSART, etc.) is added, a total of 1.5 to 2 hours is required. ### Q03If an autonomic nerve test shows an abnormality, what disease is suspected? Decreased parasympathetic function most commonly appears in the early stages of diabetic autonomic neuropathy. Decreased sympathetic function and orthostatic hypotension suggest neurodegenerative diseases such as Parkinson's disease, multiple system atrophy, and pure autonomic failure. POTS shows a pattern in which only the heart rate increases excessively when standing. ### Q04What symptoms should I get an autonomic nerve test for? Major indications for autonomic nerve tests include repeated fainting or dizziness, low blood pressure or abnormal heart rate when standing, abnormal sweating of unknown cause, digestive dysfunction (gastroparesis, constipation), and bladder dysfunction. It is also performed as a regular screening test for diabetic patients. ### Q05How are test results interpreted? The results of each test are combined to determine the presence or absence of autonomic dysfunction, type (sympathetic/parasympathetic), severity (mild/moderate/severe), and distribution (systemic/localized). Using the composite autonomic severity score (CASS), severity can be quantified on a scale of 0 to 10. ## Related articles - Amyloid PET - Cognitive function test - Electromyography - pupillometry test This article provides general medical information and does not replace an individual diagnosis or treatment plan. Please seek a medical assessment if symptoms persist. ## Important notice This Markdown alternative helps search and AI tools understand the public page accurately. It provides general health information and does not replace an individual diagnosis or treatment.