Objective: To investigate the influence of electronic filter setting change on the parameters of motor and sensory nerve conduction studies.

Method: Median motor and sensory nerve conduction studies were performed in 25 neurologically healthy adult subjects with a mean age of 29 years (range, 20∼50). Compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs) were recorded after fixing the low frequency filter cutoff value of 1 Hz, 10 Hz, 100 Hz and 300 Hz and by changing high frequency filter cutoff level from 10 KHz to 0.5 KHz. Onset and peak latency, amplitude of CMAPs and SNAPs were measured and the area of CMAPs were also recorded. Dantec Counterpoint MK2 machine was used. Skin temperature was maintained at 34^oC or above.

Results: As the high frequency filter was changed from 10 KHz to 0.5 KHz, the mean amplitude of SNAPs and CMAPs decreased by 33.5%, 3.3%, respectively. Onset and peak latency prolonged significantly below the high frequency filter level of 2 KHz (p＜0.01). When the low frequency filter was varied form 1 Hz to 300 Hz, large differences were seen in amplitude (69.7%) and area (86.5%) of CMAPs and amplitude of SNAPs (36.6%) (p＜0.01), but onset latency was not changed. Peak latency of CMAPs decreased by 20.8%, however, the peak latency of SNAPs reduced slightly (1.4%) (p＞0.01).

Conclusion: Significant alterations in parameters of CMAPs and SNAPs were produced by modification of filter setting. Optimum filter setting is recommended in nerve conduction study and filter parameters must remain constant when determining normal values and when performing serial studies on patients.

Objective: To investigate the possibility of volume conduction in the superficial radial sensory nerve conduction study in patients with a complete radial nerve injury.

Method: In patients with a complete radial neuropathy, a superficial radial sensory nerve conduction study was carried out by an antidromic and orthodromic methods. Antidromic technique was carried out by increasing stimulus intensity gradually. Median palmar cutaneous nerve conduction study was also carried out by an antidromic method.

Results: When the stimulus intensity was significantly higher than the optimal technique, a median palmar cutaneous nerve action potential was evoked instead of the superficial radial nerve action potential. This is a volume conducting potential which occurrs following a high intensity stimulus.

Conclusion: Superficial radial sensory conduction study must be carried out by an optimal stimulus intensity and an orthodromic method to eliminate the effect of volume conduction.

Method: The subjects were 50 healthy adults (mean age, 45.6 years) without the clinical signs and symptoms of peripheral neuropathy. All subjects underwent electrodiagnostic evaluation of the following sensory nerves in lower limbs: superficial peroneal, sural, proximal sural, lateral dorsal cutaneous branch of sural nerve (LDSN), and medial plantar. Examined late responses included: tibial F-wave, peroneal F-wave, and H-reflex recorded from the soleus muscle.

Results: No response rates of sensory nerve conduction studies such as superficial peroneal, sural, proximal sural, LDSN, and medial plantar nerves were 2%, 0%, 0%, 24%, and 18%, respectively. No response rates of late responses such as tibial F-wave, peroneal F-wave, and H-reflex were 0%, 2%, and 8%, respectively. And no response rates were significantly correlated with age (p＜0.05).

Conclusion: No response rate of sensory and late responses of lower limbs are relevant to age increments, the results should be considered for an early diagnosis of peripheral neuropathy in the lower limbs of old population. (J Korean Acad Rehab Med 2003; 27: 220-223)

Objective: To establish the posterior cutaneous nerve of arm (PCNA) conduction technique and set up the reference values.

Method: A PCNA conduction study was performed in 80 nerves of 40 neurologically healthy adult subjects with a mean age of 38 years (range, 20 to 56). Dantec Counterpoint MK2 machine was used. The recording bar electrodes were placed 10 cm distal to the axillary fold on a line connecting the posterior axillary fold and the olecranon. Supramaximal stimulation was applied to the axilla posterior to the brachial artery. Onset latency, baseline to peak amplitude and negative spike duration of sensory nerve action potentials were obtained. Skin temperature was measured in the posterior arm and maintained at 34^oC or above.

Results: Compound sensory action potential for the PCNA was recordable in all the subjects. The results were as follows: onset latency, 1.7⁑0.1 msec; baseline to peak amplitude, 4.6⁑1.4μV; negative spike duration, 1.1⁑0.2 msec.

Conclusion: PCNA response is readily obtainable. This study may help to assess the pain or paresthesia in the posterior aspect of the arm, although more studies are required for clinical application.