How is the sNCT/CPT procedure conducted?

The Neurometer^® CPT sNCT electrodiagnostic examination employs a standardized, automated procedure to generate objective, quantitative measures of the conduction and functional integrity of sensory nerve fibers. The unit emits non-aversive transcutaneous electrical stimuli through a pair of gold plated electrodes to quantify neuroselective CPT values. The procedure includes testing the patient at one or more body sites with three different sinusoidal frequencies of electrical stimulus. Each frequency, 2000 Hz, 250 Hz, and 5 Hz, evokes a response from a different subpopulation of sensory nerve fibers, i.e. large myelinated, small myelinated and small unmyelinated fibers, respectively. Normative ranges of CPT values have been established and published for measures taken at multiple body sites and are used to analyze patient measures. Software included with each device can be used to analyze the data and print a report summarizing the results. The following is a brief description of the standard sNCT/CPT examination.

The CPT unit is situated with its controls placed out of view of the patient. The technician turns the unit on and conducts a Pre-Exam Cable Test by following directions displayed on the unit's Liquid Crystal Display (LCD) screen. Successful completion of this test confirms the proper functioning of the CPT unit, electrodes and cables prior to each examination.

The patient is placed in a comfortable position - sitting or reclining - and preferably in a location with minimal distractions. The examination procedure is explained to the patient. The prescribed skin sites to be evaluated are examined to confirm that the skin is intact. The skin may be cleaned and prepared for testing using a skin prep-paste. A pair of 1 cm. diameter disposable gold electrodes are coated with a thin layer of conductive gel and then taped to the test site.

The patient is first presented with an Intensity Alignment procedure which quickly narrows down the threshold level to a range of +/- 50 μAmperes out of a total range of 0 to 9.99 mAmperes. Next, the patient begins the Auto Test Mode which is a fully automatic, double-blind, forced choice procedure to determine the actual Current Perception Threshold measures. The patient is presented with randomly generated pairs of real and placebo stimuli which they are then asked to identify verbally or by pressing or releasing a button on a remote unit. Based upon the patient's response, the CPT device adjusts the output level of the stimulus and randomly generates a new testing order for the next pair of tests in the series. The automated design of the sNCT/CPT testing procedure assures that neither the patient nor the operator can influence the test outcome based upon subjective impressions. When a sufficient number of tests have been performed (p<0.006), the CPT device determines and displays the CPT value for the test series and optionally prints out the results. The Auto Test Mode follows a testing paradigm similar to that used in standard auditory tests and can determine the patient's CPT measures to within +/- 20 μAmperes. Compliance Guard™ technology monitors patient responses for consistency and accuracy. This testing sequence is repeated for each of the three frequencies of stimulus before moving on to the next body site.