07/18/2013    Stephen Barrett, DPM, MBA

SudoScan (Howard Dinowitz, DPM)

Peripheral neuropathy (PN) has many etiologies,
and can have great variance from patient to
patient. As we all know, there are two components
to PN—sensorimotor and autonomic. There are
numerous ways to evaluate the sensorimotor status
of patients with PN, including, but not limited
to NCV/EMG, clinical evaluation, epidermal nerve
fiber density biopsy, high resolution diagnostic
ultrasound for entrapment, neurosensory testing
with the PSSD (pressure specified sensory
device), vibrometry, and physical evaluation to
mention a few.

However, autonomic dysfunction of the peripheral
nervous system has, up until this point, relied
solely on observation of xerotic skin, and the
failure to sweat. The SudoScan device appears to
be the first simple to use, reliable,
reproducible and objective measurement of the
ability of the eccrine glands to produce sweat,
as measured via reverse iontophoresis to
determine the level of Chloride ions excreted by
the patient after low voltage galvanic
stimulation of the hands and feet.

Thermoregulatory control of sweating is
intimately linked to the autonomic nervous system
via sympathetic C fibers, and sweat glands are
richly endowed with a neuropeptidergic
innervation. This valuable estimate of the
autonomic function of the patient has significant
ramifications, which may in fact save lives, as
we know that cardiac autonomic neuropathy can
account for mortality. Low conductance will also
indicate a dry foot, which is at higher risk for
cracking, ulcers and infection.

The SudoScan can pick up the severity of the
autonomic dysfunction thereby giving insight into
other autonomic pathology, which is so prevalent
in the diabetic patient, and effective treatment
planning. Moreover, quantifying this disturbance
in sweating may be useful in monitoring responses
to therapeutic intervention. We now have the
technological power to take advantage of this
physiological arrangement to better understand,
monitor, and treat disorders of small nerve
fibers and the somatic and autonomic nervous
system (ANS). This method of sudomotor function
testing is rapid, noninvasive, not technically
demanding, and accessible to the outpatient
clinic.

Regarding whether the use of the SudoScan is
within the scope of podiatric practice seems
purely intuitive, and is entirely within the
purview of the podiatric physician, just as you
would evaluate the glucose level of a diabetic
patient on the morning of the surgery.
Podiatrists are trained to effectively evaluate
systemic disease as it affects the foot and
ankle, and perioperative management of lower
extremity pathology.

The fact that the hands are also being tested non-
invasively with this device is no different than
when a podiatrist evaluates a complete blood
study to see if the patient is an acceptable
surgical candidate. If pathology is present, then
the ordering podiatric physician makes
appropriate referral after review of the
results.

There is simply no other specialty that deals
with the amount of peripheral neuropathy than
podiatrists, and this device will allow for
another objective measurement increasing their
arsenal.

Stephen Barrett, DPM, MBA, Vice President,
Association for Extremity Nerve Surgeons (AENS),
sbarrett@barrettmed.com

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