**History/Background/and/or General Information**

The autonomic nervous system (ANS) is a regulatory branch of both the central
and peripheral nervous system, which controls and regulates the autonomic
functions within the body through sympathetic and parasympathetic nerves.
These functions include regulation of blood pressure, heart rate, airway size
and airflow to the lungs, digestive tract functions, sweat production, bladder
control, and sexual function. The ANS acts through a balance of its own two
components, the sympathetic and parasympathetic nervous systems. Autonomic
failure consists of impaired or absent function of autonomic responses, which
may be sympathetic or parasympathetic or both and can involve specific organ
systems or can be generalized. There are other autonomic disorders that
consist of excessive function of autonomic responses. The concept of an
imbalance between opposing autonomic systems is applicable to some disorders,
such as some cardiac arrhythmias, but not in all autonomic disorders.
Autonomic disorders may be congenital or acquired - primary or secondary. If
it becomes unbalanced, a person may experience a variety of symptoms that are
sometimes vague and can affect many bodily functions. To the specialist, the
presentation of autonomic dysfunction can be specific and diagnosed with
simple clinical tests. Autonomic testing, properly performed and interpreted,
is helpful toward achieving diagnostic specificity. Autonomic failure is
associated with increased morbidity and mortality. Orthostatic hypotension is
associated with an increased risk of falls and impairment in activities of
daily living.  
  
ANS testing can be grouped into the following general categories:

  1. Cardiovagal innervation \- a test that provides a standardized quantitative evaluation of vagal innervation to parasympathetic function of the heart.  Responses are based on the interpretation of changes in continuous heart recordings in response to standardized maneuvers and include heart rate response to deep breathing, Valsalva ratio, and 30:15 ratio heart rate responses to standing.
  2. Vasomotor adrenergic innervation - evaluates adrenergic innervation of the circulation and of the heart in autonomic failure. The following tests are included: beat-to-beat blood pressure and R-R interval response to Valsalva maneuver, sustained hand grip, and blood pressure and heart rate responses to tilt-up or active standing.
  3. Sudomotor - function testing is used to evaluate and document neuropathic disturbances that may be associated with pain. The quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test (TST), sympathetic skin responses, and silastic sweat imprints are tests of sympathetic cholinergic sudomotor function. 

The QSART measures axon reflex-mediated sudomotor responses quantitatively and
evaluates post-ganglionic sudomotor function. Recording is usually carried out
from the forearm and three lower extremity skin sites to assess the
distribution of post-ganglionic deficits.  

The TST evaluates the distribution of sweating by a change in color of an
indicator powder. This test has a high sensitivity, and its specificity for
delineating the site of lesion is greatly enhanced when used in conjunction
with QSART.

Sweat imprints are formed by the secretion of active sweat glands into a
plastic (silastic) imprint. The test can determine sweat gland density, a
histogram of sweat droplet size and sweat volume per area.



  4. Combined cardiovagal and vasomotor adrenergic innervation testing (CPT code 95924) of the autonomic nervous system is specifically of parasympathetic function and vasomotor adrenergic function using at least a 5-minute tilt with a passive tilt table. 

Appropriate application and interpretation of ANS testing requires a detailed
knowledge of the testing criterion and a match between the tests of suspected
clinical/functional impairment with the autonomic activity being tested. Most
autonomic disorders are diagnosed clinically, with laboratory and formal
diagnostic testing when ordered and performed appropriately playing both a
primary diagnostic and an adjunctive or confirmatory role. Testing may also be
appropriate to monitor disease progression when there is a change in clinical
status or to evaluate a patient's response to specific treatment for an
autonomic disorder.

**Covered Indications:**

Autonomic function testing is covered as reasonable and necessary when used as
a diagnostic tool to evaluate symptoms indicative of vasomotor instability,
such as hypotension, orthostatic tachycardia, and hyperhidrosis after more
common causes have been excluded by other testing, and the ANS testing is
directed at establishing a more accurate or definitive diagnosis or
contributing to clinically useful and relevant medical decision making for one
of the following indications:

  1. To diagnose the presence of autonomic neuropathy in a patient with signs or symptoms suggesting a progressive autonomic neuropathy.
  2. To evaluate the severity and distribution of a diagnosed progressive autonomic neuropathy.
  3. To differentiate the diagnosis between certain complicated variants of syncope from other causes of loss of consciousness.
  4. To evaluate inadequate response to beta blockade in vasodepressor syncope.
  5. To evaluate distressing symptoms in a patient with a clinical picture suspicious for distal small fiber neuropathy in order to diagnose the condition.
  6. To differentiate the cause of postural tachycardia syndrome.
  7. To evaluate change in type, distribution, or severity of autonomic deficits in patients with autonomic failure.
  8. To evaluate the response to treatment in patients with autonomic failure who demonstrate a change in clinical exam.
  9. To diagnose axonal neuropathy or suspected autonomic neuropathy in the symptomatic patient.
  10. To evaluate and treat patients with recurrent unexplained syncope to demonstrate autonomic failure, after more common causes have been excluded by other standard testing.

**Equipment for Autonomic Nervous System Studies**

General professional standards apply for all equipment. Unknown algorithms
untested on the Medicare population in systematic trials do not constitute the
professional component of diagnostic testing. Equipment with FDA clearance for
heart rate variability measurements in response to paced respirations and
exercises that tests only heart rate variability does not meet the full range
of testing parameters required for the performance of testing of autonomic
nervous system function cardiovagal innervation (parasympathetic function) and
vasomotor adrenergic innervation and does not ensure full test requirements,
such as blood pressure monitoring, nor do they incorporate proper testing
conditions, such as the use of a tilt table. Providers may be asked to supply
information on the equipment used to perform autonomic nervous system studies
to ensure that all studies performed meet the requirements of the procedure.

**Limitations:**

Syndromes of autonomic dysfunction for which ANS testing might add valuable
clinical information are relatively rare. Generally, only after excluding more
common causes of autonomic signs or symptoms (e.g., hypotension,
hyperhidrosis, and orthostatic tachycardia) may formal autonomic testing be
indicated to exclude or confirm autonomic disorders. The following indications
are not considered medically reasonable and necessary and will not be covered:

  * To screen patients without signs or symptoms of autonomic dysfunction, including patients with diabetes, hepatic or renal disease;
  * Testing for the sole purpose of monitoring disease intensity or treatment efficacy in diabetes, hepatic or renal disease;
  * Testing where the results are not used in clinical decision-making and patient management;
  * Testing performed by physicians who do not have evidence of training, and expertise to perform and interpret these tests. Testing must be done for an accepted clinical indication by a properly trained examiner and interpreted by qualified individuals within their scope of practice (weekend courses may not demonstrate expertise). Physicians must have knowledge, training, and expertise to perform and interpret these tests, and to assess and train personnel working with them. This training and expertise must have been acquired within the framework of an accredited residency and/or fellowship program or must reflect extensive continued medical education activities. If these skills have been acquired by way of continued medical education, the courses must be comprehensive, and designated for the American Medical Association (AMA) category I credit by an ACCME (Accreditation Council for Continuing Medical Education) or SMS (State Medical Society) accredited CME provider.

Diagnostic testing may be allowed once to confirm or exclude specific
autonomic disease. For patients with diagnosed autonomic disorders, repeat
testing is governed by a change in clinical status or response to a
therapeutic intervention. If a repeat test is needed, it is not expected to
exceed once per year.

Providers who perform these tests on an unusually high proportion of their
patients, or at frequencies exceeding once per year may be subject to medical
review.

As published in the CMS IOM Publication 100-08, Medicare Program Integrity
Manual, Chapter 13, Section 13.5.4, an item or service may be covered by a
contractor LCD if it is reasonable and necessary under the Social Security Act
Section 1862 (a)(1)(A). Contractors shall determine and describe the
circumstances under which the item or service is considered reasonable and
necessary.

**Provider Qualifications:   **

A qualified physician for this service/procedure is defined as follows: A)
Physician is properly enrolled in Medicare. B) Training and expertise must
have been acquired within the framework of an accredited residency and/or
fellowship program in the applicable specialty/subspecialty in the United
States or must reflect equivalent education, training, and expertise endorsed
by an academic institution in the United States and/or by the applicable
specialty/subspecialty society in the United States.

For guidelines regarding general supervision during performance of a
procedure, please refer to 42 CFR Section 410.32 Diagnostic x-ray tests,
diagnostic laboratory tests, and other diagnostic tests: Conditions.

For guidelines regarding studies performed in an Independent Diagnostic
Testing Facility (IDTF), please refer to 42 CFR Section 410.33 Independent
diagnostic testing facility.