Search

PURPOSE This study is to determine the diagnostic utility of optimal recording electrode placement for distal latency comparison of median-second lumbrical and ulnar-interossei/third lumbrical (M2L-UI3L) in carpal tunnel syndrome. METHODS Sixty-five hands of control and 75 hands of 62 clinically suspected carpal tunnel syndromes were used for the M2L-UI3L and standard conduction studies. To obtain optimal M2L-UI3L, the recording active electrode (E1) was placed at the midpalm over the third metacarpal bone, whereas the reference electrode (E2) was attached to the palmar digital crease area. Then, median and ulnar nerves were stimulated on the wrist each at 8 cm proximal to E1. M2L-UI3L and standard nerve conduction studies were performed. Sensitivity and specificity of M2L-UI3L were measured in the diagnosis of mild carpal tunnel syndrome. RESULTS For statistical analysis, the receiver operating characteristics and Student t-test were used. The area under the receiver operating characteristic curve of M2L-UI3L was 0.993. Diagnostic cutoff value of M2L-UI3L greater than 0.6 milliseconds yields sensitivity of 93% and specificity of 97%. The distal median motor latency to the second lumbrical alone showed the area under the curve of 0.998, and the diagnostic cutoff value greater than 3.4 milliseconds yields sensitivity of 96% and specificity of 100%. CONCLUSIONS This technique for M2L-UI3L shows high sensitivity and specificity compared with the previous reports on the diagnosis of carpal tunnel syndrome. Furthermore, the values of median-second lumbrical motor latency alone have higher sensitivity and specificity, comparable with the median sensory conduction study across the wrist segment.

OBJECTIVE To determine normal values for the amplitude ratio of sensory nerve action potential (SNAP) from an ulnar sensory segmental nerve conduction study, and to the evaluate usefulness in the diagnosis of mild-degree ulnar neuropathy at the elbow (UNE). DESIGN Segmental sensory conduction study of the ulnar nerve was performed in 71 healthy subjects. Peak latency and baseline to peak amplitudes were measured. The amplitude ratio of below-elbow to wrist (BE/W) stimulations and above-elbow (AE) to below-elbow stimulations (BE) were calculated. Normal cutoff values were obtained by subtracting 2 SD from the mean value, and these values were applied to 22 symptomatic UNE cases. The amplitude ratio was also obtained in six subjects with C8 radiculopathy. RESULTS The amplitude ratios of BE/W and AE/BE were 0.61 +/- 0.08 and 0.82 +/- 0.08, respectively. The cutoff value of BE/W was 0.45, and that of AE/BE was 0.65. The amplitude ratio of BE/W showed a weak correlation to the length of the forearm segment (r = -0.25, P < 0.05). Five of the 22 UNE patients revealed only reduced amplitude ratios of SNAP across the lesion, whereas all the patients with C8 radiculopathy showed normal amplitude ratios of ulnar SNAP. CONCLUSIONS The amplitude ratio of ulnar SNAPs may be useful in the diagnosis of mild ulnar neuropathy with only sensory symptoms and normal segmental motor conduction.

By using a fixed 8-cm distance between the stimulating and recording electrodes, we describe a new approach to peroneal nerve motor conduction studies to the proximal muscles. The recording active electrodes were fastened over the tibialis anterior and peroneus longus, while the stimulating cathode was placed at the posterolateral border of the fibular neck. The skin temperature was maintained at or above 32 degrees C in the lateral surface of the proximal shin. In normal subjects, 81 deep and superficial peroneal nerves were tested to establish reference values. The latencies to the tibialis anterior and peroneus longus were 2.5 +/- 0.3 (range, 2-3) ms and 2.6 +/- 0.2 (range, 1.9-3) ms, respectively. The amplitudes of compound muscle action potential for deep and superficial peroneal nerves were 6.2 +/- 1.3 (range, 3.6-9.3) and 6.2 +/- 1.7 (range, 3.4-10.6) mV, respectively. Also, 17 adult onset diabetic patients were tested for comparison. We concluded that this alternative test to the conventional methods is accessible for electrophysiologic evaluation of peroneal neuropathy.

It has been reported that the quantity of fibrillation potentials (FP) decreases with drop in the intramuscular temperature. However, the quantitative measurement of the FP with intramuscular temperature changes has not been reported. Under anesthesia of intraperitoneal sodium pentobarbital, the sciatic nerve of 6 rats (Sprague-Dawley) was surgically isolated. A 1-cm segment was excised after tying the proximal and distal ends of the nerve segment. A concentric needle electrode and thermometer needle probe were inserted approximately 1-cm apart into the posterior tibial muscles 3 to 4 days after the nerve segment excision. Before and during cooling the muscles with ice, FPs were evoked and printed on paper recording for later analysis. Visually recognizable potentials (30 microV or above) in each printed tracing with temperature changes (range, 37 degrees C to 15 degrees C) were manually counted. A positive linear correlation was found between the intramuscular temperature changes and the quantity of FPs. The recording of FP completely ceased at about 20 degrees C below baseline temperature. In this study, we have successfully semiquantified fibrillation potentials in a wide range of intramuscular temperature changes.

Medial femoral cutaneous nerve (MFCN), a sensory branch of the femoral nerve, supplies the skin on the anterior medial aspect of the thigh and knee. A conduction study for this nerve is described. A recording electrode was placed anterior-medially in the thigh and 14 cm distal to the stimulating cathode that was placed immediately lateral to the femoral artery just below the inguinal ligament. Sixty-four nerves of 32 adults with a mean age of 40 yr (range, 21-56) were tested. The latencies to the onset and peak were 2.4 +/- 0.2 and 2.9 +/- 0.2 ms, respectively. The amplitude of baseline to negative peak was 4.9 +/- 1.0 microV. The conduction velocity calculated by the distance divided by the onset latency was 60 +/- 5 m/s. We conclude that the MFCN is accessible for electrophysiologic evaluation, which may help in diagnosing the MFCN or femoral neuropathy.

Objective: To determine the clinical usefulness of the compound nerve action potential of the common peroneal nerve recorded immediately distal to or at the fibular neck, at the same time stimulating the common peroneal nerve laterally at the posterior knee. Design: For recording the compound nerve action potential of the common peroneal nerve, the active recording electrode was secured just distal to or at the fibular neck area, whereas the stimulating electrode was placed on the medial border of the lateral hamstring tendon at the level of the popliteal crease. To reduce shock artifacts, a biphasic stimulation was used. Results: In 35 adults (n = 19 men), 70 nerves were tested. The compound nerve action potential from each individual was recorded. The compound nerve action potential amplitude of a baseline-to-negative peak and conduction velocity were measured on both sides. For comparisons of the side-to-side amplitude and conduction velocity, Wilcoxon's signed-rank test was applied. Conclusion: This approach of recording the compound nerve action potential of the common peroneal nerve, in addition to conventional methods, may enhance the process of determining the precise localization of peroneal nerve lesion in the knee.

Lateral ankle or foot pain may have various etiologies including entrapment of or injury to the distal sural nerve or early peripheral neuropathy. Antidromic distal sural conduction studies have not been used in clinical neurophysiologic evaluation, however, for technical reasons. The purpose of this study was to determine if by modifying recording parameters and using electronic averaging adequate responses could be obtained to permit standardization of distal sural conduction. Standard surface recording electrodes with an inter-electrode separation of 37 mm were used. The distal sural nerve conduction of 40 healthy adult subjects (mean age = 33 +/- 9 yr, range = 23 to 52) was measured. The latency to the onset was 3.2 +/- 0.4 ms (range = 2.5 to 4.0 ms) and to the negative peak was 3.9 +/- 0.5 ms (range = 3.0 to 4.9 ms). The conduction velocity was 38 +/- 5 m/s (range = 30 to 48 m/s). The amplitude measured from baseline to negative peak was 5.8 +/- 2.1 microV (range = 3.0 to 11.0 microV). The results indicated that electrodiagnostic evaluation of the distal sural nerve could be readily achieved and that this might be useful in differential diagnosis.

Ankle or foot pain may be due to various clinical conditions. Injury or entrapment of the deep peroneal sensory nerve is part of the differential diagnosis; however, no technique studying the deep peroneal sensory conduction velocity has been described. We describe a technique that is simple and reproducible with averaging. We electrophysiologically studied the deep peroneal sensory nerve in 40 neurologically healthy adult subjects. The latency to onset of the sensory action potential was 2.9 +/- 0.4 ms (range = 2.1-3.6 ms). The latency to the peak of the sensory action potential was 3.6 +/- 0.4 ms (range = 2.7-4.2 ms). The conduction velocity was 42 +/- 5 m/s (range = 33-53 m/s). The amplitude was 3.4 +/- 1.2 microV (range = 1.6-6.6 microV). We conclude that the deep peroneal sensory nerve is readily accessible for electrophysiologic evaluation. It may be of value in diagnosing deep peroneal nerve pathology.

The tibialis posterior can be a valuable muscle in the electrodiagnostic evaluation of the sacral plexus, lumbosacral roots, lower extremity neuropathies and tibial nerve lesions. It may be under utilized, however, because it is generally considered to be inaccessible to needle examination. The purpose of this study was to compare the widely recommended posterior approach to this muscle to an anterior approach that we define. In six cadaver legs, the safe access to this muscle via the anterior approach was 16.8 +/- 5 mm by contrast to 9.5 +/- 2 mm by the posterior approach. We conclude that the anterior approach to needle electromyography of the tibialis posterior muscle is easier, safer and deserves more widespread practice.