Autonomic Nervous System Testing

POLICY NUMBER

L.2.01.418

DESCRIPTION

The autonomic nervous system (ANS) controls physiologic processes that are not under conscious control. ANS testing consists of a battery of tests intended to evaluate the integrity and function of the ANS. These tests are intended as adjuncts to the clinical examination in the diagnosis of ANS disorders.

Autonomic Nervous System

The autonomic nervous system (ANS) has a primary role in controlling physiologic processes not generally under conscious control. They include heart rate, respirations, gastrointestinal (GI) motility, thermal regulation, bladder control, and sexual function. The ANS is a complex neural regulatory network that consists of two complementary systems that work to maintain homeostasis: the sympathetic and the parasympathetic systems. The sympathetic nervous system is responsible for arousal, and sympathetic stimulation leads to increased pulse, increased blood pressure (BP), increased sweating, decreased GI motility, and an increase in other glandular exocrine secretions. This is typically understood as the “fight or flight” response. Activation of the parasympathetic nervous system will mostly have the opposite effects; BP and pulse will decrease, GI motility increases, and there will be a decrease in sweating and other glandular secretions.

ANS Disorders

ANS disorders, also called dysautonomias, are heterogeneous in etiology, clinical symptoms, and severity. ANS disorders can be limited and focal, such as patients with isolated neurocardiogenic syncope or idiopathic palmar hyperhidrosis. At the other extreme, some ANS disorders can be widespread and severely disabling, such as multiple systems atrophy, which leads to widespread and severe autonomic failure.

Symptoms of autonomic disorders can vary, based on the etiology and location of dysfunction. Cardiovascular manifestations are often prominent. Involvement of the cardiovascular system causes abnormalities in heart rate control and vascular dynamics. Orthostatic hypotension and other manifestations of BP lability can occur, causing weakness, dizziness, and syncope. Resting tachycardia and an inability to appropriately increase heart rate in response to exertion leads to exercise intolerance. There is a 2- to 3-fold higher incidence of major cardiac events in patients with diabetic autonomic neuropathy (myocardial infarction, heart failure, resuscitation from ventricular arrhythmia, angina, or the need for revascularization). There is also an increase in sudden cardiac death and overall mortality for these patients.

Many other organ systems can be affected by autonomic neuropathy. Involvement of the bladder can lead to incomplete emptying, resulting in urinary retention and possible overflow incontinence. GI involvement is commonly manifested as gastroparesis, which is defined as slowed gastric emptying and can cause nausea, vomiting, and a decreased tolerance for solid food and large meals. Constipation may also occur if the lower GI tract is involved. Impairment of sexual function in males can manifest as erectile dysfunction and ejaculatory failure. Dysfunction of thermal regulation and sweating can lead to anhidrosis and heat intolerance. Paradoxically, excessive sweating can also occur as a compensatory mechanism in unaffected regions.

A classification of the different types of autonomic dysfunction, adapted from Freeman and Macdougall and McLeod, can be made as follows:

• Diabetic autonomic neuropathy

• Amyloid neuropathy

• Immune-mediated neuropathy

  • Rheumatoid arthritis

  • Systemic lupus erythematosus

  • Sjögren syndrome

• Paraneoplastic neuropathy

• Inflammatory neuropathy

  • Guillain-Barré syndrome

  • Chronic inflammatory demyelinating polyneuropathy

  • Crohn disease

  • Ulcerative colitis

• Hereditary autonomic neuropathies

• Autonomic neuropathy secondary to infectious disease

  • HIV disease

  • Lyme disease

  • Chagas disease

  • Diphtheria

  • Leprosy

• Acute and subacute idiopathic autonomic neuropathy

• Toxic neuropathies.

Other chronic diseases may involve an ANS imbalance, without outright dysfunction of the nerves themselves. Approximately 40% of individuals with essential hypertension will show evidence of excess sympathetic activity. Sympathetic overactivity is also a prominent feature of generalized anxiety, panic disorder, and some types of depression, as well as certain cardiac disorders such as chronic heart failure. These types of ANS imbalances are not usually classified as ANS disorders.

Treatment Much of the treatment for autonomic disorders is nonpharmacologic and supportive. However, there are specific actions that can improve symptoms in patients with specific deficits. For patients with orthostatic hypotension, this involves adequate intake of fluids and salt, moving to an upright position slowly and deliberately, use of lower-extremity compression stockings, and keeping the head of the bed elevated 4 to 6 inches (10-15. cm). In severe cases, treatment with medications that promote salt retention, such as fludrocortisone, is often prescribed. Patients with symptoms of hyperhidrosis may benefit from cooling devices and potent antiperspirants such as Drysol, and patients with decreased tearing and dry mucous membranes can use over-the-counter artificial tears or other artificial moisturizers.

ANS Testing ANS testing consists of a battery of tests. Any single test may be performed individually, or the entire battery of tests may be ordered. Individual components of testing may include cardiovagal function testing, sudomotor function, salivation testing, and tilt table testing.

• Cardiovagal Function Testing

  • Beat-to-beat variability in the heart rate can be measured at rest, or in response to provocative measures, such as deep breathing or the Valsalva maneuver. Reduced, or absent, heart rate variability is a sign of autonomic dysfunction.

  • Baroreflex sensitivity is measured by examining the change in pulse and heart rate variability in response to changes in BP. A medication such as phenylephrine is given to induce a raise in BP, and baroreflex sensitivity is calculated as the slope of the relation between heart rate variability and BP.

• Sudomotor Function (Sweat Testing) - Sweat testing evaluates the structure and function of nerves that regulate the sweat glands.

  • Quantitative Sudomotor Axon Reflex Test (QSART)

    - The QSART is an example of a commercially available semiquantitative test of sudomotor function. The test is performed by placing the color-sensitive paper on the skin, which changes color on contact with sweat. Measurement of the amount of color change is a semiquantitative measure of sudomotor function.

  • Silastic Sweat Imprint- Silastic material is placed on the skin, and the sweat droplets form indentations on the silastic surface, allowing quantitation of the degree of sweating present. The Neuropad test is an example of a commercially available silastic sweat imprint.

  • Thermoregulatory Sweat Test - A more complex approach in some centers is the use of a thermoregulatory laboratory. This is a closed chamber in which an individual sits for a defined period under tightly controlled temperature and humidity. An indicator dye is brushed on the skin, and it changes color when in contact with sweat. Digital pictures are taken and projected onto anatomic diagrams. Computer processing derives values for a total area of anhidrosis and the percent of anhidrotic areas.

  • Sympathetic skin response tests use an electric current to stimulate sympathetic nerves. The tests measure the change in electrical resistance, which is altered in the presence of sweat. In general, these tests are considered to be sensitive but have high variability and potential for false-positive results.

  • A variant of sympathetic skin response testing is electrochemical sweat conductance measured by iontophoresis (eg, Sudoscan). In this test, a low-level current is used to attract chloride ions from sweat glands. The chloride ions interact with stainless-steel plate electrodes to measure electrochemical resistance.

• Salivation Testing - The protocol for salivation testing involves the subject chewing on a preweighed gauze for 5 minutes. At the end of 5 minutes, the gauze is removed and reweighed to determine the total weight of saliva present.

• Tilt Table Testing - Tilt table testing is intended to evaluate for orthostatic intolerance. The patient lies on the table and is strapped in with a foot rest. The table is then inclined to the upright position, with monitoring of the pulse and BP. Symptoms of lightheadedness or syncope in conjunction with changes in pulse or BP constitute a positive test. A provocative medication, such as isoproterenol, can be given to increase the sensitivity of the test.

Composite Autonomic Severity Score The Composite Autonomic Severity Score, which ranges from 0 to 10, is intended to estimate the severity of autonomic dysfunction. Scores are based on self-reported symptoms measured by a standardized symptom survey. Scores of 3 or less are considered mild, scores of 3 to 7 are considered moderate, and scores greater than 7 are considered severe.

Since 1976, numerous ANS testing devices have been cleared for marketing by the U.S. Food and Drug Administration through the 510(k) process.

Autonomic Nervous System Test Devices

POLICY

Autonomic nervous system (ANS) testing, including parasympathetic function (cardiovagal innervation), sympathetic adrenergic function (vasomotor adrenergic innervation), and sudomotor function (quantitative sudomotor axon reflex test [QSART], thermoregulatory sweat test [TST], and silastic sweat imprint test), may be considered medically necessary for use as a diagnostic tool to evaluate symptoms of vasomotor instability after more common causes have been excluded by other testing, for any of the following:

1. Diagnose the presence of autonomic neuropathy in a patient with signs or symptoms suggesting a progressive autonomic neuropathy, including:

• Diabetic neuropathy

• Amyloid neuropathy

• Sjogren’s syndrome

• Idiopathic neuropathy

• Pure autonomic failure

• Multiple system dystrophy

2. Evaluate the severity and distribution of a diagnosed progressive autonomic neuropathy;

3. Differentiate the diagnosis between certain complicated variants of syncope from other causes of loss of consciousness;

4. Evaluate inadequate response to beta blockade in vasodepressor syncope;

5. Evaluate distressing symptoms in the patient with a clinical picture suspicious for distal small fiber neuropathy in order to diagnose the condition;

6. Differentiate the cause of postural tachycardia syndrome;

7. Evaluate change in type, distribution or severity of autonomic deficits in patients with autonomic failure;

8. Evaluate the response to treatment in patients with autonomic failure who demonstrate a change in clinical exam;

9. Diagnose axonal neuropathy or suspected autonomic neuropathy in the symptomatic patient;

10. Evaluate and diagnose sympathetically maintained pain, as in reflex sympathetic dystrophy or causalgia; or

11. Evaluate and treat patients with recurrent unexplained syncope to demonstrate autonomic failure.

Autonomic nervous system (ANS) testing is considered investigational for all other indications that do not meet the above criteria, including but not limited to:

1. Screening or routine testing of patients without signs or symptoms of autonomic dysfunction, including patients with diabetes, hepatic or renal disease;

2. Testing for the sole purpose of monitoring disease intensity or treatment efficacy in diabetes, hepatic or renal disease;

3. Patients with a clearly diagnosed somatic neuropathy, especially demyelinating neuropathies;

4. Patients with uncomplicated vasovagal syncope;

5. General diagnosis of conditions including, but not limited to:

• Asthma

• Anxiety and/or stress

• General wellness

• Obesity

• Psychological conditions

• Post-partum dysfunctions

• Sleep apnea

• Chronic fatigue syndrome

• Fibromyalgia

• Allergic Conditions

• Hypertension

Sympathetic skin response (SSR) testing is considered investigational.

Quantitative direct and indirect axon reflex testing (QDIRT) is considered investigational.

POLICY EXCEPTIONS

Federal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

Although there is no standard battery of tests for autonomic nervous system (ANS) testing, a full battery generally consists of individual tests in 3 categories.

• Cardiovagal function (heart rate variability, heart rate response to deep breathing and Valsalva maneuver)

• Vasomotor adrenergic function (blood pressure response to standing, Valsalva maneuver, and hand grip, tilt table testing)

• Sudomotor function (Quantitative Sudomotor Axon Reflex Test, quantitative sensory test, Thermoregulatory Sweat Test, silastic sweat imprint, sympathetic skin response, electrochemical sweat conductance).

At least one test in each category is usually performed. More than one test from a category will often be included in a battery of tests, but the incremental value of using multiple tests in a category is unknown.

There is little evidence on the comparative accuracy of different ANS tests, but the following tests are generally considered to have uncertain value in ANS testing:

• Pupillography

• Pupil edge light cycle

• Gastric emptying tests

• Cold pressor test

• Quantitative direct and indirect testing of sudomotor function test

• Plasma catecholamine levels

• Skin vasomotor testing

• The ANSAR® test.

ANS testing should be performed in a dedicated ANS testing laboratory. Testing in a dedicated laboratory should be performed under closely controlled conditions, and results should be interpreted by an individual with expertise in ANS testing. Testing using automated devices with results interpreted by computer software has not been validated and thus has the potential to lead to erroneous results.

Medically Necessary is defined as those services, treatments, procedures, equipment, drugs, devices, items or supplies furnished by a covered Provider that are required to identify or treat a Member's illness, injury or Mental Health Disorders, and which Company determines are covered under this Benefit Plan based on the criteria as follows in A through D:

A. consistent with the symptoms or diagnosis and treatment of the Member's condition, illness, or injury; and

B. appropriate with regard to standards of good medical practice; and

C. not solely for the convenience of the Member, his or her Provider; and

D. the most appropriate supply or level of care which can safely be provided to Member. When applied to the care of an Inpatient, it further means that services for the Member's medical symptoms or conditions require that the services cannot be safely provided to the Member as an Outpatient.

For the definition of medical necessity, “standards of good medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. BCBSMS makes no payment for services, treatments, procedures, equipment, drugs, devices, items or supplies which are not documented to be Medically Necessary. The fact that a Physician or other Provider has prescribed, ordered, recommended, or approved a service or supply does not in itself, make it Medically Necessary.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

05/01/2013: New policy added. Approved by Medical Policy Advisory Committee.

02/27/2015: Policy reviewed. Policy statement updated to add chronic fatigue syndrome, fibromyalgia, allergic conditions, and hypertension as investigational conditions. Sources section updated.

08/21/2015: Code Reference section updated for ICD-10.

06/06/2016: Policy number L.2.01.418 added. Policy Guidelines updated to add medically necessary and investigative definitions.

06/29/2018: Policy description extensively re-written. Policy statements unchanged. Policy Guidelines updated regarding ANS testing.

07/05/2019: Policy reviewed; no changes.

12/21/2021: Code Reference section updated to revise ICD-10 diagnosis code description for code range M35.00 - M35.09.

03/14/2024: Policy reviewed. Policy statements unchanged. Policy Guidelines updated to change "Nervous/Mental Conditions" to "Mental Health Disorders" and "Medically Necessary" to "medical necessity."

03/28/2025: Policy reviewed; no changes.

SOURCE(S)

1. Blue Cross Blue Shield of Texas medical policy, Autonomic Nervous System (ANS) Testing

2. Blue Cross Blue Shield Association policy # 2.01.96

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.

Covered Codes

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