Early Detection of Peripheral Neuropathy by Assessment of Sudomotor Function
David Whaley, Slav Danev, Michael Alexander, Jonathan R.T. Lakey
Chronic hyperglycemia in both type 1 and type 2 diabetes commonly lead to diabetic peripheral
neuropathy (DPN) which commonly affects small nerve fibers, including autonomic sudomotor nerves,
of the lower limbs. DPN results from nerve damage leading to gradual onset of foot pain, tingling,
numbness, muscle weakness, extreme sensitivity to touch, and heat intolerance. Peripheral neuropathy
is associated with increased all-cause mortality and morbidities such as foot ulcers, poor wound healing,
local and systemic infection, limb amputation, and painful neuropathic symptoms. DPN is also typically
diagnosed during later stages when disease progression has already led to irreversible nerve damage
and associated severe symptoms. As such, early detection of peripheral neuropathy is important in
implementing early interventions and can help preserve nerve function and prevent serious complications
of DPN.
Non-invasive methods of testing for early DPN rely on assessment of sudomotor nerve function. One
method includes quantitative sudomotor axon reflex test (QSART) which measures postganglionic
sympathetic function via iontophoresis which allows quantification of sweat production, and by
extension, autonomic function. In general, QSART provides a non-invasive, reproducible, and precise
evaluation of autonomic function in both controls and diabetics. It can be used to evaluate a large
number of autonomic diseases, and the quantitative data it generates provides a measure of the extent
and location of the peripheral neuropathy in each individual. Another assessment method includes the
sympathetic skin response (SSR) test which measures the change in electrical potential of the skin which
itself comes from activated eccrine sweat glands. The SSR test has a well-established protocol, and the
results are easily-measured, and the results are quantifiable. It can be used reliably in the diagnosis of
numerous autonomic disorders including DPN where a diminished or absent response correlate with
sudomotor nerve damage.
SudoCheck by VitalScan is an FDA-cleared, non-invasive autonomic sdomotor assessment tool that
combines QSART, SSR, BIA, and EIS to provide rapid results with a specificity of 95% and a sensitivity
of 80%. It was created to enable a precise evaluation of sweat gland function, and by extension, the
presence and progression of diabetic peripheral neuropathy including early sub-clinical disease.
