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 More than 30 years after leaving the laboratory for clinical applications
ranging from Podiatry to Neurology and dozens of other specialties
in-between, the Neurometer®
evaluation is proven to provide unique functional diagnostic measures of
sensory nerve conduction thresholds (sNCTs). We use minimum amounts of
painless electrical stimulus to consistently elicit a nerve response, the Current Perception Threshold (CPT).
Specific diagnostic applications for polyneuropathy, radiculopathy and other
conditions are reviewed below.
The Neurometer diagnostic neurostimulator generates a constant current
stimulus by monitoring and compensating for tissue impedance variations. The
stimulus evokes responses that quantify the functional integrity of each of
the three major sub-populations of sensory nerve fibers. Specifically, Aβ,
Aδ & C fiber groups are selectively stimulated by sinusoid waveform currents
of 2000 Hz, 250 Hz and 5 Hz respectively. Using small surface electrodes,
this test generates discrete double-blinded CPT measures (p<0.006)
representing minimum detectable current intensities (+/- 20 μAmp.) for each
fiber type.
Advantages of the Neurometer Evaluation
Common metabolic/toxic and progressive neuropathies affect sensory nerves
before motor nerves. Affected sensory nerves pass through reversible stages
of hyperesthesia (often sub-clinical) then hypoesthesia and anesthesia.
These sensory impairments occur in specific nerve fiber sub-populations. CPT
studies have the unique capacity to evaluate the full spectrum of sensory
nerve function in all the major fiber sub-populations. Patients are
frequently asymptomatic in the earliest stages. The earliest stage of the
pathologic process is usually the easiest phase to effectively intervene.
The Neurometer detects hyperesthetic sensory neuropathy in non-diabetics
with impaired glucose tolerance and in non-diabetic obese individuals. This
ability to detect subclinical abnormalities in conditions known to carry a
high risk of polyneuropathy is a tremendous clinical diagnostic advantage.
It also detects the hypoesthesia of advanced neuropathic conditions as well
as nerve regeneration.
A table is provided
presenting a comparison of features between various neurodiagnostic testing
procedures.
Research publications confirm that sensory impairments ranging from polyneuropathies
(diabetic, demyelinating, toxic) to compressive lesions (Carpal Tunnel
Syndrome), radiculopathies, spinal cord lesions as well as regeneration may
be neuroselectively evaluated. Additional applications of the Neurometer
include pharmaceutical, cosmetic, environmental and laboratory animals.
The Neurometer
Evaluation
Automated double-blind testing methodology is used to
determine the painless measures. It is based on the same psycho-physical principles used
in routine hearing tests. The painless stimulus is characterized as
“tingling”, “prickling”, or “buzzing”. Qualitative measures such as warm,
cold, vibration, touch etc. are not a factor.
Electrodes are positioned at the prescribed test site and held in place with
tape. Directions for the technician are displayed on the LCD screen. The
subject is instructed to press a button until a stimulus is detected at the
site of the electrode(s) and then release the button. At this point the
painless CPT
measure is verified using Compliance Guard®
software. This effectively
monitors responses for consistency. Depending on the
test mode the
standardized automated double-blind CPT measures from all 3 major
sub-populations of nerve fibers requires 3-8 minutes per nerve/site. CPT measures are then classified by
comparison to the internationally validated normative database.
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