Slowed conduction velocity of the median sensory nerve across the carpal tunnel in normal adults

OBJECTIVE: To examine the difference of using onset or peak latency in the segmental conduction study of the median nerve in normal adults without carpal tunnel syndrome. DESIGN: We investigated 60 hands of 30 young healthy adults (15 men and 15 women; mean age, 27.1 yrs; range, 18-36 yrs). We performed the mid-palm segmental conduction study using antidromic and orthodromic techniques in the median sensory nerves of the second and third digits and the onset and peak latencies of the proximal (wrist-palm) and distal (palm-digit) segments were measured. The distoproximal latency ratios were compared between onset and peak latencies and were compared with the ratios of the superficial radial sensory nerve. RESULTS: Distoproximal peak latency ratios in the median and superficial radial sensory nerves were always >1.0 in both the antidromic and orthodromic conduction studies. However, distoproximal onset latency ratios in the median sensory nerve were >1.0 in only 35% and 21.7% of second digits and in only 25% and 11.7% of third digits in orthodromic and antidromic studies, respectively (P < 0.05). The results of distoproximal onset latency ratios in the superficial radial sensory nerve were 93.3% in the orthodromic study and 86.7% in the antidromic study (P < 0.05). CONCLUSION: Prolongation of onset latency across the carpal tunnel during segmental conduction study of the median sensory nerve was common in healthy adults. When comparing proximal and distal segments for diagnosis of carpal tunnel syndrome, using onset latency as a diagnostic variable may cause greater reporting of false positives.     

Effect of gender on orthodromic sensory nerve action potential amplitude

OBJECTIVE: Studies in the literature have demonstrated a gender effect on sensory nerve action potential (SNAP) amplitude for the median and ulnar nerves by use of the antidromic method of recording. The objective of this study was to determine if performing orthodromic sensory nerve stimulation eliminates the gender bias by removing the finger circumference as a variable. METHODS: Fifty-five healthy subjects participated in the study. The mean age of the subjects was 37.8 +/- 5.9 yr and 35.3 +/- 5.9 yr for men and women, respectively. Orthodromic sensory nerve conduction studies were performed for the median and ulnar nerves measuring the SNAP amplitude by use of standard electrophysiologic technique. RESULTS: The mean finger circumference of the third digit was 6.5 +/- 0.58 cm for men and 5.9 +/- 0.47 cm for women, and for the fifth digit, it was 5.6 +/- 0.41 cm for men and 5.3 +/- 0.37 cm for women. The median SNAP amplitude and their percentiles of 2.5 and 97.5 for the median nerve were 30.0 microV for men and 28.0 microV for women. For the ulnar nerve, they were 16.5 microV for men and 16.0 microV for women. CONCLUSION: The study confirmed that orthodromic sensory nerve stimulation did not have any significant effect on SNAP amplitude between men and women.     

Sensitivity of median sensory nerve conduction tests in digital branches for the diagnosis of carpal tunnel syndrome

OBJECTIVE: To compare the sensitivity of median sensory nerve conduction tests performed by stimulating digital branches in patients with carpal tunnel syndrome. DESIGN: A prospective study in 506 hands of patients with carpal tunnel syndrome diagnosed electrophysiologically. RESULTS: The sensitivity of median sensory nerve conduction tests across the first three digit-to-wrist segments and palm-to-wrist segment was determined. The most common abnormal electrophysiologic finding was the slowing of sensory nerve conduction velocity over the palm-to-wrist segment, which was detected in 98.5% of the hands. Slowing of sensory nerve conduction velocity over the digit 1-, 2-, and 3-to-wrist segments of the median nerve was found in 95.4%, 88%, and 82% of the hands, respectively. CONCLUSION: The sensory nerve conduction velocity test of the digit 1-to-wrist segment has the most sensitivity among the three digital branches of the median sensory nerve, and it may be used more widely in the electrodiagnosis of carpal tunnel syndrome.     

Across-elbow ulnar nerve sensory conduction technique

Compression of the ulnar nerve across the elbow is one of the most common of the entrapment syndromes. The usual method of electrodiagnostic evaluation is to determine the motor nerve conduction for this nerve segment. Normal values for sensory conduction and amplitude changes for this nerve segment have been rarely reported, and clinical usefulness of the sensory techniques remains unclear and controversial. This study reports an ulnar nerve sensory technique for the across-elbow segment. Normal data with the elbow flexed to 90 degrees and for a 10-cm nerve segment were 1.8msec, mean +2SD for sensory latency measured to onset and 1.9msec to peak. Comparable motor latency was 2.0msec. Sensory amplitude decrement across the elbow was 41% mean +2SD and 7.6% for the comparable motor amplitude decrement. Three cases of ulnar nerve compression at the elbow are reported, exemplifying that this technique appears to be useful particularly in patients with sensory, as opposed to mixed (sensory and motor), clinical abnormalities.     

Deep peroneal sensory nerve. Standardization in nerve conduction study

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.     

Differences in sensory conduction velocity between different sensory branches and segments of the median and ulnar nerves

Abnormality of absolute values of median sensory conduction velocities and differences in conduction velocity between median and ulnar nerves are used as criteria for abnormality in the diagnosis of carpal tunnel syndrome. Detailed studies of sensory conduction in various median and ulnar branches and segments indicate that conduction velocities measured and calculated by standard methods are different in the different nerves, segments and branches. In particular, the velocity in the middle digit branch of the median nerve is slower than that in the index, and that in the 3-4 palmar branch is slower than that in the 2-3 palmar branch. Median and ulnar sensory conduction velocities are not well correlated in the same hand in the same individual, so comparison of these nerves for diagnostic purposes is subject to some risk. Palmar and digital conduction velocity in the same nerve may not be identical and the median nerve may have asymptomatic palmar slowing of no clinical significance. The conclusion that abnormality is present must take these factors into account.     

Evaluation of sensory nerve conduction velocity testing of the superficial radial nerve

The purposes of this study were to evaluate the methods for examining the superficial radial nerve and to compare velocities and amplitudes of responses based on electrode shape and placement and site of stimulation. We selected 51 subjects with a mean age of 37 years from a healthy group. Twenty additional subjects with a mean age of 28 were also examined. Nerve conduction was done by stimulating over the dorsal forearm and lateral arm and recording from the superficial radial nerve where its branches cross the extensor pollicis longus tendon. The second group of subjects were stimulated at the same site and also at the elbow. Recording was done with a rectangular-shaped electrode placed in the area between the extensor pollicis longus and the extensor pollicis brevis tendons. We found a mean conduction velocity of 61 m/sec +/- 4.91 in the first group with a mean amplitude of response of 36.7 microV +/- 11.7 when we stimulated at the forearm site and 4.06 microV +/- 6.75 when we stimulated at the lateral arm site. In the second group of subjects, conduction velocity from lateral arm to forearm site was 63 m/sec +/- 4.50; from the lateral arm to elbow, 66 m/sec +/- 10.4; and from the elbow to the forearm site, 64 m/sec +/- 9.71. Amplitudes of response were 43.8 microV +/- 14.45 at the forearm stimulation site, 18.06 +/- microV +/- 7.37 at the elbow site, and 6.7 microV +/- 4.25 at the lateral arm site. We compared the mean velocities from the two methods and found no significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasound effects on electroneuromyographic measures in sensory fibers of the median nerve

The purpose of this study was to clarify the available literature and study the influence of ultrasound on the conduction velocity and amplitude of evoked sensory potentials in the median nerve. Thirteen subjects were assigned to either Experimental or Control Groups for ultrasound or placebo treatments. We compared sensory-nerve conduction velocity in the median nerve after 10 minutes of ultrasound treatment at three intensity levels (0.5, 1.0, and 1.5 W/cm2) with sensory-nerve conduction velocity in the median nerve after 10 minutes of placebo ultrasound treatment (0.0 W/cm2). No significant differences were noted between groups at any of the three ultrasound intensity levels, nor were the interaction effects significant. A hypothetical model, based on the available literature, proposes that ultrasound-induced changes in sensory-nerve conduction velocity may not progress in a direct linear fashion relative to the duration of treatment.     

Temperature effect on antidromic and orthodromic sensory nerve action potential latency and amplitude

The measurement of sensory nerve action potential (SNAP) latency and amplitude is often necessary to accurately diagnose disorders of peripheral nerves. The sensory evoked response can be obtained using either the antidromic (AD) or orthodromic (OD) technique. In a previous study we demonstrated that in healthy subjects the AD SNAP distal latency of median and ulnar nerves at 14 cm distance is approximately 0.2 msec slower than the OD SNAP distal latency at 32C. The AD SNAP amplitude was also two times greater than the OD SNAP amplitude. In this study we observed that these differences between the AD and OD SNAP latency and amplitude varied significantly as temperature changed. The AD median nerve SNAP distal latency was delayed by .06 msec/degree with cooling. The OD median nerve SNAP distal latency was delayed by .03 msec/degree with cooling. These values represent less of a slowing per degree centigrade cooling than has been previously noted in the literature. The median nerve SNAP amplitude was found to increase with upper extremity cooling with the AD and OD technique by 3.5 microV and 0.5 microV per degree, respectively. For accurate interpretation of SNAP latency and amplitude, the electromyographer must be familiar with the technique used and the differing effect of the temperature with each technique.     

Tourniquet obliteration of exercise-induced sensory nerve conduction augmentation.

OBJECTIVE: We previously discovered that minimally suprathreshold sensory nerve action potential amplitudes increased during isometric muscle contraction. In this study, the hypothesis was that the exercise-induced response could be blocked with a tourniquet. METHODS: A total of 21 healthy male and female subjects were recruited from the medical center. Baseline and postevent serial sural nerve recordings were made in the leg of 16 healthy subjects under the following conditions: (1) blood pressure cuff inflation at the arm, (2) isometric muscle contraction in the hand, and (3) conditions 1 and 2 combined. RESULTS: Results showed there was a 2.9 microV increase in the sural nerve response 5 min after muscle contraction compared to baseline at rest. The exercise-induced sensory response was largely obliterated by the blood pressure cuff with exception of the 1-min postexercise recording. CONCLUSION: In conclusion, the results show a tourniquet placed on the proximal arm blocks the effect of the muscle contraction of the hand on the minimally suprathreshold sensory sural nerve conduction recording in the ankle. The likely reason for this is the interruption of a thus far unidentified circulating factor. The clinical implication is the discovery of a sensory regulatory mechanism controlled by the motor system.     

Effect of technique variation on sensory nerve conduction characteristics

The impact of technique variation on the wave-form characteristics of the evoked sensory potential was determined from the median and ulnar nerves of healthy subjects. The conduction characteristics of latency, amplitude, and duration were determined for orthodromic and antidromic techniques of stimulation as measured under each of three recording modes: 1) single evoked response, 2) superimposition, and 3) electronic averaging. Variation in the technique of stimulation significantly affected each of the three wave-form characteristics. Peak latency and duration of the evoked sensory potential were longer in antidromic stimulation. The amplitude of the sensory potential varied significantly with both recording and stimulating techniques. The amplitude of the sensory response was larger in antidromic stimulation than in orthodromic stimulation and also was found to be smaller with electronic averaging than with the other recording modes in both antidromic and orthodromic conduction techniques. This degree of variation requires that standardized techniques of methodology be established with the development of normal values for the particular laboratory.     

Automated sensory nerve conduction testing using fuzzy logic.

Nerve conduction studies continue to be an important tool in the evaluation of peripheral nerve disorders but have come under increased scrutiny because of heightened cost control in health care service delivery. In selected clinical settings, automated nerve conduction studies may be a useful clinical tool replacing conventional testing, but existing instruments are limited and have not generally been accepted into clinical practice. Further advancements in nerve conduction automation may be possible by incorporating expert system approaches into nerve conduction measurement and control algorithms. Using fuzzy logic techniques to duplicate the reasoning strategies of experienced electrodiagnostic clinicians, a software controller was developed to automatically perform sensory nerve conduction studies. The fuzzy logic system successfully performed 88% of 97 sensory studies in a mixed group of normal and patient populations. Sensory nerve action potential latency and amplitude measures obtained with automated testing were the same as determined by clinicians. Failures were related to design limitations of the controller, noise, and artifact. The high negative predictive value and sensitivity of fuzzy logic based testing suggest that its utility is in minimizing the need for unnecessary conventional electrodiagnostic studies in patients with normal nerve function. Fuzzy logic appears to be a useful approach to nerve conduction automation that can model expert reasoning and judgment.     

Interexaminer repeatability of antidromic ulnar sensory nerve conduction velocity measurements

OBJECTIVE: To determine the interexaminer repeatability of the ulnar antidromic sensory nerve conduction velocity (NCV). DESIGN: Test-retest design. Based on a randomization list of various combinations and sequences from 2 of a total of 3 examiners, the measurement was repeated within half an hour by a second examiner blinded to the results of the first examiner. SETTING: Outpatient department. PARTICIPANTS: Twenty-four consecutive healthy subjects (mean age, 38 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The intraclass correlation coefficient (ICC) and the coefficient of repeatability (CR) were determined for the below elbow to wrist (BE-to-W), above elbow to below elbow (AE-to-BE), and axilla to above elbow (AX-to-AE) segments. RESULTS: The ICC was .42 for the BE-to-W, .15 for the AE-to-BE, and -.05 for the AX-to-AE segment. The CR was 12.2m/s for the BE-to-W, 16.2m/s for the AE-to-BE, and 21.4m/s for the AX-to-AE segment. CONCLUSIONS: During the assessment of the antidromic sensory NCV of the ulnar nerve, a moderate amount of interexaminer variability must be taken into account for the BE-to-W segment. More proximally, an extremely large amount of interexaminer variability must be taken into account. This calls into question the usefulness of the antidromic ulnar sensory NCV for the AX-to-AE and AE-to-BE segments.     

双侧正中神经、尺神经多节段运动神经传导各参数正常值的建立

目的：建立双侧正中神经、尺神经多节段运动神经传导速度（MCV）、潜伏期(LAT)和波幅(AMP)的正常值。方法：200例健康志愿者,男100例,女100例,分别按年龄分成5组,正中神经记录点在拇短展肌,刺激点分别为掌点、腕点、肘点、腋点、Erb点;尺神经记录点在小指展肌,刺激点分别为腕点、肘下点、肘上点、腋点、Erb点,记录各段MCV、LAT、AMP值。结果：正中神经、尺神经多节段MCV 、LAT、AMP与性别、侧别无相关性;年龄与正中神经各段MCV、LAT、AMP及尺神经AMP有关。 结论：双侧正中神经、尺神经多节段运动神经传导的准确检测对临床疾病诊断有重要价值。     

Ulnar palmar cutaneous nerve and hypothenar sensory conduction studies.

The ulnar palmar cutaneous nerve (UPCN) is potentially useful to the electrodiagnostician. However, no definitive nerve conduction study techniques for the UPCN have been reported. The UPCN supplies sensory innervation to the hypothenar palm. This study describes an orthodromic sensory conduction technique for the hypothenar palm. Data were collected from 20 normal limbed patients (ages 22-58). Potentials were recorded over the ulnar nerve 10cm proximally and at the elbow. Distal latency was 2.19 +/- 0.17msec, and distal amplitude was 12.7 +/- 6.9uv. Additionally, a modified collision technique was used in several subjects to examine the possibility of volume conduction to more than one ulnar nerve branch. The techniques described may be useful in selected cases of distal ulnar nerve pathology. A case is reported in which injury to the superficial sensory branch of the ulnar nerve, with sparing of the UPCN was demonstrated electrodiagnostically. Further study is needed to determine if the UPCN can consistently be electrophysiologically isolated.