Help Available for Hard-to-diagnose
This article originally appeared in Pathways, a magazine
published for physicians and the community by UMass Memorial Medical
When a patient presents with a history of fainting or any orthostatic
symptoms, a diagnostic work up to rule out cardiac etiologies and seizure
disorders is appropriate. If this process yields no definitive answer,
dysfunction of the autonomic nervous system (ANS) may be the culprit. Now,
thanks to an investment in state-of-the-art equipment, autonomic function
testing (AFT) is available at UMass Memorial Medical Center. In fact, the
Medical Center is home to one of only a handful of comprehensive AFT labs in the
"There are thousands of
patients who suffer from conditions relating to autonomic dysfunction,"
explained Peter Novak, MD, PhD, a board-certified neurologist who heads the AFT
Lab at UMass Memorial. "But they can be very hard to diagnose because
disturbances in ANS function can produce a wide variety of symptoms. These
include syncope, dizziness, chronic pain, bladder urgency or frequency, fatigue,
nausea, palpitations, abnormal sweating, bloating or cramping after meals,
constipation, or skin color changes.
"Many patients and their doctors are frustrated when these symptoms become
disabling, and there are no definitive answers as to what is causing them," he
continued. "With AFT, we can accurately and reliably establish whether
dysfunction of the autonomic nervous system is the cause, providing answers so
that appropriate treatment can be given."
"Syncope is a fairly common clinical symptom," noted Lan Qin, MD, PhD, a
board-certified neurologist and fellowship-trained neurophysiologist at the
Medical Center. "Abnormalities of the autonomic nervous system can be found in
75 percent of syncope patients who don't have heart diseases or seizure
disorders. We would not be able to accurately diagnose this group of patients
Specialized Testing Provides Objective Measurement
AFT entails several specialized tests to monitor blood pressure, blood flow,
heart rate, skin temperature and sweating. By measuring these functions, it is
possible to evaluate quantitatively the functioning of the autonomic nervous
system and correlate signs and symptoms of possible autonomic dysfunction with
this objective measurement in a way that is clinically useful. Tests include:
- The tilt-table test which measures heart rate and beat-to-beat blood
pressure response to tilt-up for evaluation of orthostatic hypotension
- The heart rate response to deep breathing (HRDB) test, used to evaluate
- The Valsalva maneuver, where a patient blows into a tube to increase
pressure in the chest, used to measure heart rate and beat-to-beat blood
pressure changes and to evaluate the cardiovagal and peripheral adrenergic
- Sudomotor testing, including the quantitative sudomotor axon reflex test,
which measures skin vasomotor function by assessing the small autonomic nerve
fibers which control the sweat glands, and the thermoregulatory sweat test, a
test of sympathetic nerves that supply the skin, which evaluates and documents
neuropathic disturbances that may be associated with pain.
The Value of Skin Biopsy Testing
In addition, the UMass Memorial Autonomic Function Testing Laboratory offers
skin biopsy testing to detect small-fiber neuropathy. Dr. Qin explained why this
testing is very important:
"Because one of my practice areas is neuromuscular diseases, I see a lot of
patients with neuropathy," she said. "Conventional electromyography usually can
detect large-fiber neuropathy, so an EMG study for patients with small-fiber
neuropathy could be normal, especially in the early stages.
"It is important to detect small-fiber neuropathy early because studies show
that it could be the first sign of diabetes," she continued. In fact, one study
showed that in 40 percent of patients with small-fiber neuropathy diagnosed only
after skin biopsy, oral glucose tolerance testing revealed a previously
undetected impaired glucose tolerance.
"Early detection of small-fiber neuropathy leads to early screening for
diabetes or glucose intolerance, and early lifestyle or pharmacological
interventions," she added.
In addition, skin biopsy testing demonstrates small-fiber neuropathy in
restless legs syndrome and erythromelalgia. Plus, in systemic diseases, such as
lupus, sarcoidosis, Sjögren's syndrome, celiac disease and hypothyroidism, skin
biopsy testing has enabled correlations between neuropathic symptoms and
Indications for AFT
When is a referral for AFT appropriate? "In general, when an autonomic
abnormality is suspected, or if it is unclear whether a common condition, such
as chronic fatigue or orthostatic symptoms, are neurological or not, laboratory
evaluation of the autonomic nervous system is appropriate," Dr. Novak said.
For example, sexual dysfunction may be the manifestation of disorders
affecting the ANS. AFT directly estimates the extent of involvement of the
sympathetic and parasympathetic nervous systems - particularly important in
evaluating patients with erectile dysfunction who may have both organic (such as
those with diabetes) and psychogenic etiologies.
In addition, disorders of bowel motility, such as achalasia, intestinal
pseudo-obstruction, chronic recurrent abdominal pain, and unexplained diarrhea
or constipation, are increasingly linked to generalized autonomic abnormalities.
Urinary frequency or retention may be an early symptom of ANS disease. Sweating
abnormalities, such as hyperhidrosis or heat intolerance, are measured directly
by AFT that includes quantitative sweat monitoring. And silent cardiac ischemia
in diabetic patients may be due to autonomic impairment, but because moderate
dysautonomia may produce few symptoms, it can remain undiagnosed without AFT.
Postural orthostatic tachycardia (POTS) syndrome, common in young women,
occurs when unexplained tachycardia accompanies orthostatic symptoms. Correctly
recognizing the problem can prevent unnecessary procedures such as
radiofrequency ablation or pacemaker placement. What is more, chronic fatigue
syndrome may result from chronic orthostatic hypotension. AFT can identify
patients who will benefit from treatment of orthostasis, enabling many to resume
a normal lifestyle.
The Ultimate Benefit
Providing timely, accurate diagnostic information to identify the most
appropriate therapy is the ultimate benefit of AFT, Drs. Novak and Qin
emphasized. "It's gratifying to be able to give patients and their physicians
answers to previously unexplained problems so that they know what is going on
and what to do about it," Dr. Novak said. AFT also can be used to monitor the
response to therapy.
"AFT is noninvasive and painless, except for the skin biopsy, which is
nothing more than a big scratch," he added. "Testing is done on an outpatient
basis and takes only about 60 to 90 minutes, depending on the number of studies
administered. And it is covered by insurance."