Endocrinologists use the painless, non-invasive sNCT electrodiagnostic examination procedure to evaluate metabolic
polyneuropathies commonly observed in clinical endocrinology. Annual sNCT
evaluations for patients at risk for polyneuropathy (e.g. diabetes,
hypothyroidism) are recommended to objectively assess the presence or
absence of a polyneuropathy or evaluate its progression. Particular concern
is given to evaluating protective sensation. Normal sNCT evaluation results
indicate that no further sNCT testing beyond an annual exam is necessary
unless a change in the clinical condition suggesting sensory dysfunction
warrants a repeat evaluation.
Patients with certain types of endocrine disorders (e.g. diabetes) are
susceptible to developing compressive neuropathies and radiculopathies and
testing for these conditions may be required based upon the clinical
impression that the differential diagnosis of a patient's sensory impairment
may includes these conditions.
The sNCT procedure had its origins in the
evaluation of diabetic patients at the Johns Hopkins University
School of Medicine, Department of Neurology beginning in the early 1980's.
This clinical research led the FDA to grant permission to market the
Neurometer CPT device in 1986. Presently, there are more than 700 peer
reviewed articles demonstrating clinical utility of the sNCT evaluation.
Approximately 20% of these papers are devoted to diabetes.
The sNCT is the only electrodiagnostic sensory evaluation able to
quantify both hyperesthesia and hypoesthesia. Hyperesthetic conditions
reflect inflamed or irritated sensory nerve fibers that have not yet lost
their functioning but have abnormally low electrical excitatory response
thresholds. Hypoesthesia, differs in that it is associated
with a more advanced stage of neuropathy and represents a loss of function.
Hyperesthesia occurs before hypoesthesia in progressive peripheral nerve
damage. Detection of hyperesthesia permits earlier therapeutic
intervention, thereby improving the prognosis with the potential of
limiting more severe damage and reducing the cost of care.
demonstrate the sNCT evaluation ability to detect and evaluate
hyperesthesia in 50% of the neurologically asymptomatic diabetic subjects as
well as non-diabetic obese individuals. Studies shows that in those
diabetics with clinical signs of neuropathy about 75% of the abnormalities
were hyperesthetic. Diabetics with foot ulcerations, in contrast, had more than 98% of
their measures hypoesthetic.
The sNCT evaluation is also the only electrodiagnostic procedure capable of
selectively evaluating the functional integrity of the large myelinated,
small myelinated and unmyelinated sensory nerve fibers. This is particularly
important for diabetic subjects because diabetic neuropathy is not selective
for a specific sub-population of sensory nerve fibers. For instance, the
sNCT evaluation can detect small unmyelinated fiber neuropathy in diabetic
subjects who have normal myelinated fiber function. Numerous studies have
demonstrated that the sNCT evaluation is able to selectively evaluate small
fiber function while the other neurodiagnostic tests such as the Nerve
Conduction Velocity (NCV) lack this ability.
Small fiber functioning represents protective sensation. Protective
sensation is extremely important because it is the loss of protective
sensation that can lead to "painless neuropathy" and amputation. Small unmyelinated fiber function is
also correlated with autonomic nerve integrity. Autonomic neuropathy is
responsible for the majority of deaths occurring among diabetic patients and
the ability to easily assess unmyelinated nerve function with the sNCT
evaluation allows early identification of those patients at risk for related
The sNCT evaluation is the only electrodiagnostic procedure which can test
at the tips of the toes and fingers where the distal axonal neuropathies
commonly begin in diabetics. This allows the sNCT evaluation to detect
diabetic neuropathy months or years before it would be detectable by other
procedures such as the sensory Nerve Conduction Velocity (NCV) exam or Skin
Punch Biopsy (SPB). The
tuning fork evaluation is not capable of selectively assessing large fiber
function in the tip of the great toe because vibration is conducted by bone
conduction proximally and the loss of sensation can not be isolated to a
specific location. Also, unmyelinated fibers can be polymodal and respond to
a mechanical stimulus such as vibration, mono-filament pressure or pin-prick. As a consequence, patients with a
selective loss of large fiber function may show up normal with these evaluations.
Another type of polyneuropathy reported to
occurs in diabetes is immune mediated. This type of polyneuropathy presents
with an asymmetric distribution of sensory dysfunction which can occur
anywhere but typically occurs around the dorsal root ganglia. The sensory
NCV evaluation is limited to testing the physiological integrity of the
peripheral distal segment of nerves, and diabetic patients with proximal
immune mediated lesions of peripheral sensory nerves have normal peripheral
sensory NCVs. Studies from Columbia University, New York Medical College and
St. Vincents Medical Center in New York, University of Louisville School of
Medicine and the United States Air Force, have documented the ability of the
sNCT evaluation to detect and quantify these proximal demyelinating
Diabetics may also suffer from a vascular or circulatory related peripheral
neuropathy. These neuropathies may be focal and can effect sensory
function anywhere on the body. The sNCT evaluation is unique because it can
be used to test any cutaneous body site which allows the clinician to
objectively quantify this condition.
One additional and important consideration about the sNCT evaluation is that
it is painless. This feature encourages far better patient compliance for
repeated evaluation than the painful NCV or SPB. The painless
nature of the sNCT procedure is also of particular value in enhancing
compliance for the
electrodiagnostic analysis of juvenile diabetic patients.
Endocrinologists primarily use sNCT/CPT
studies to objectively evaluate the impact of diabetic and pre-diabetic
conditions to monitor and guide their patient’s medical management. The
Neurometer® CPT evaluation is prescribed by the endocrinologist when
clinical examination findings are equivocal or suggest the development of an
impairment in distal sensory function and an objective evaluation is
required to confirm and evaluate a diagnosis of polyneuropathy. Typically,
the distal great toe test site is tested bilaterally and if a polyneuropathy
is detected then therapeutic interventions or modifications are considered
to attempt to reverse the condition and/or prevent its progression. Normal
CPT evaluation results indicate that no further CPT testing is necessary
unless a change in the clinical condition or laboratory findings suggesting
sensory dysfunction requires an evaluation.
See related Publications.
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