Objective: To investigate the influence of five different recording electrodes on the various parameters of sensory nerve action potentials (SNAPs).

Method: Median sensory nerve conduction study was performed in 50 normal subjects using different five types of recording electrodes-disc electrode, ring electrode, bar electrode and two kinds of felt-tip bar electrodes (type 1 and 2). The interelectrode distances between active and reference electrodes were set at 4 cm for the disc and ring electrodes. The bar electrode, felt-tip electrodes type 1 and 2 were fixed at interelectrode distances of 3 cm, 3.7 cm and 2.3 cm, respectively. Onset and peak latency, onset to peak amplitude, peak to peak amplitude and duration of negative spike of SNAPs were measured. These parameters were compared using ANOVA test.

Results: Onset and peak latencies of SNAPs recorded from five different electrodes were not different (p＞0.05). Onset to peak and peak to peak amplitudes of SNAPs recorded from felt-tip type 2 electrode were significantly reduced compared to other electrodes (p＜0.05). Onset to peak amplitude of SNAPs was also reduced when the ring electrode was used (p＜0.05). The negative spike durations of SNAPs recorded from felt-tip type 2 and bar electrodes were shorter than other electrodes recording (p＜0.05).

Conclusion: Onset and peak latencies of SNAPs were not affected by the types of electrodes used. Shortening of interelectrode distance may be a main cause of reduction of peak to peak amplitude and negative spike duration of SNAPs.

Objective: To establish the reference values of the sensory conduction for all the digits in the hand, conduction studies were performed using the standard technique.

Method: One hundred hands of fifty neurologically healthy adults with mean age of 45 years (range, 23∼69) were tested. Depending on ages, the 50 adults were devided into three groups: group 1, 20∼45 years old; group 2, 46∼60 years old; group 3, 61∼ years old. Antidromic sensory nerve conduction techniques using a fixed distance were performed. The onset latency and baseline to peak amplitude of the sensory nerve action potentials (SNAPs) were measured. During the test, the skin temperature of the hand was maintained at 34^oC or above. These variables from SNAPs were compared according to age, gender, side, and recording digits.

Results: Comparison of the median and ulnar SNAPs between age groups revealed longer onset latency and smaller amplitude in the elderly group. The amplitude of SNAPs was larger in females than in males and the left side than the right side. Comparison of the latencies and amplitudes between the second and third digits showed no significant difference statistically. Also, the latencies and amplitudes of the median and ulnar nerves recorded from the fourth digits showed no significant difference statistically.

Conclusion: Based on these results, the reference values for sensory conductions from all the digits were obtained. These values would be helpful in evaluation of CTS or unspecified finger pain or upper extremity neuropathy.

Objective: To evaluate the usability of near-nerve needle recording techniques in cases of unrecordable sensory nerve action potentials (SNAPs) with a surface electrode and to determine a proper alternative value of the missing latencies.

Method: Twenty six hands of 23 patients with a carpal tunnel syndrome (CTS) and an unobtainable median SNAP by surface electrode were evaluated by the near-nerve needle recording of median SNAPs. Using the nerve conduction data of 113 patients with CTS, we have established 3 alternative values: maximal, 95 percentile and predictive latencies. The alternative values were compared with the mean onset latencies by the near-nerve needle recordings of median SNAPs.

Results: Median SNAPs were obtainable in the 22 out of 26 hands by the near-nerve recording technique. The mean onset latency was 5.51⁑0.36 ms. The alternative values from 113 patients with CTS were as follows: maximum latency, 6.9 ms; 95 percentile latency, 5.6 ms; and predictive latency, 5.52 ms (Y = ⁣0.123* X ⁢ 5.52491; Y, onset latency; X, amplitude; r²=0.564; p=0.00). The Predictive latency was nearest to the mean onset latency.

Conclusion: To minimize the selection bias and statistical errors, the near nerve recording techniques proved to be a valuable method in cases of unrecordable SNAPs with surface electrode. For compensation of missing data, a proper alternative value can be obtained by the predictive latency calculated from a linear regression.