Early Detection of Peripheral Neuropathy by Assessment of Sudomotor Function

Abstract

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.