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.     

正常人周围神经传导速度40例分析

目的:研究健康成人周围神经运动传导速度(motor-nerveconductionve-locity,MCV)和感觉传导速度(sensory-nerveconductionvelocity,SCV)的正常值,为诊断周围神经疾病提供依据。方法:健康志愿者40例,年龄22～53岁,男女各20例。分别检测双侧正中神经、尺神经、胫神经及腓神经MCV和双侧正中神经、尺神经及胫神经SCV。分析指标包括潜伏期、波幅及神经传导速度(nerveconductionvelocity,NCV)。结果:NCV在正常人男女之间、左右侧肢体之间的差异在统计学上无显著性意义(P>0.05),并且随着年龄的增加而逐渐减慢。结论:NCV检测是周围神经病的重要诊断技术之一,而正常值的确定是临床诊断的前提。不同年龄组应采用各自的正常值。     

New criteria for sensory nerve conduction especially useful in diagnosing carpal tunnel syndrome

This article reports a technique for determining new standard values for median sensory nerve latencies, amplitudes, and durations. Use of these values should significantly improve the ability to diagnose carpal tunnel syndrome and to reduce the number of false negative results. Forty-five median sensory nerves of 30 neurologically healthy subjects were evaluated with rigid techniques and temperature control at stimulation and recording points. Latencies for antidromic and orthodromic conduction from wrist-to-thumb, wrist-to-index finger, wrist-to-middle finger, and wrist-to-ring finger (all 14 cm distances) are reported. Conduction time for nerve impulses through the transcarpal segment via ulnar and radial nerves was also measured for comparison with median nerve latencies. In addition to latency measurements, characteristics of electrical responses evoked by stimulation were described. These include amplitude of the recorded response measured from baseline to negative peak and from negative peak to positive peak, duration of the negative response wave (from baseline to return to baseline) and duration measured from onset of the negative wave to the positive peak. According to our data, a distal median nerve sensory latency of more than 3.3 ms (the mean of 2.9 ms plus two standard deviation values of 0.18 ms) when measured to the peak of the negative wave is indicative of abnormality.     

Ultrasound imaging of the carpal tunnel during median nerve compression

Median nerve (MN) compression is a recognized component of carpal tunnel syndrome (CTS). In order to document compressive changes in the MN during hand activity, the carpal tunnel was imaged with neuromuscular ultrasound (NMUS). Ten patients with CTS and five normal controls underwent NMUS of the MN at rest and during dynamic stress testing (DST). DST maneuvers involve sustained isometric flexion of the distal phalanges of the first three digits. During DST in the CTS patients, NMUS demonstrated MN compression between the contracting thenar muscles ventrally and the taut flexor tendons dorsally. The mean MN diameter decreased nearly 40%, with focal narrowing in the mid-distal carpal canal. Normal controls demonstrated no MN compression and a tendency towards MN enlargement, with an average diameter increase of 17%. Observing the pathologic mechanism of MN injury during common prehensile hand movements could help better understand how to treat and prevent CTS.     

Day-to-day variability of median nerve location within the carpal tunnel

Background

Carpal tunnel syndrome is a commonly encountered entrapment disorder resulting from mechanical insult to the median nerve. Magnetic resonance imaging (MRI)-based investigations have documented typical locations of the median nerve within the carpal tunnel; however, it is unclear whether those locations are consistent within an individual on different days.

Methods

To determine the day-to-day variability of nerve location, 3.0 T MRI scans were acquired from six normal volunteers over multiple sessions on three different days. Half of the scans were acquired with the wrist in neutral flexion and the fingers extended, and the other half were acquired with the wrist in 35° of flexion and the fingers flexed. Prior to half of the scans (in both poses), subjects performed a preconditioning routine consisting of specified hand activities and several repetitions of wrist flexion/extension. The shape, orientation, location, and location radius of variability of the median nerve and three selected flexor tendons were determined for each subject and compared between days.

Findings

Two of the six subjects had substantial variability in nerve location when the wrist was in neutral, and four of the subjects had high variability in nerve position when the wrist was flexed. Nerve variability was typically larger than tendon variability. The preconditioning routine did not decrease nerve or tendon location variability in either the neutral or the flexed wrist positions.

Interpretation

The high mobility and potential for large variability in median nerve location within the carpal tunnel needs to be borne in mind when interpreting MR images of nerve location.     

Sensitivity, specificity, and variability of nerve conduction velocity measurements in carpal tunnel syndrome

OBJECTIVE: To explore the diagnostic values of 8 commonly used electrodiagnostic techniques for measuring median nerve conduction velocity (NCV) in carpal tunnel syndrome (CTS). DESIGN: Sensitivity and specificity analyses. SETTING: A hospital-based electrodiagnostic laboratory. PARTICIPANTS: Forty-four normal hands and 136 symptomatic hands. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: (1) Long-segment studies: antidromic wrist-to-digit sensory NCV without subtraction, (2) short-segment studies: transcarpal palm-to-wrist mixed NCV without subtraction, and (3) 2 segment studies: antidromic transcarpal sensory NCV with subtraction (differential calculation from wrist-to-digit and palm-to-digit segments). Both onset and peak latency values were obtained for calculating the NCV. Sensitivity, specificity, and coefficient of variance were calculated for each NCV study. RESULTS: The short-segment, onset latency-based transcarpal mixed NCV yielded the highest sensitivity (75%). CONCLUSIONS: Results from measurement of a single, short-nerve segment tended to be superior to results obtained by either long-segment studies or differential subtraction between 2 segments of the same nerve in the electrodiagnosis of CTS. Explanations for our results are offered from both electrophysiologic and statistical perspectives.     

Reduced longitudinal excursion of the median nerve in carpal tunnel syndrome

OBJECTIVE: To determine if longitudinal excursion of the median nerve is reduced in patients with carpal tunnel syndrome (CTS). DESIGN: Case-control study. SETTING: University human movement laboratory. PARTICIPANTS: Nineteen patients with CTS (8 men, 11 women; mean age, 57+/-15 y), and 37 healthy controls (8 men, 29 women; mean age, 48+/-10 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Longitudinal excursion of the median nerve, and the ratio of nerve to flexor digitorum superficialis tendon excursion at the carpal tunnel evoked by finger extension. Measurements were taken using a validated Doppler ultrasound technique, and tests were conducted with the elbow positioned in extension and flexion. RESULTS: Mean longitudinal excursion of the median nerve was significantly greater in controls (11.2+/-2.8 mm) than patients (8.3+/-2.6 mm) with the elbow extended (P=.013), but not with the elbow flexed (controls, 12.5+/-2.5 mm; patients, 10.2+/-3.1 mm; P=.089). Mean nerve/tendon excursion ratios were significantly greater in controls (.32+/-.07) than patients (.23+/-.06), with the elbow extended (P<.001), and flexed (controls, .36+/-.06; patients, .28+/-.10; P=.019). Discriminant analysis identified that 11 (58%) of the 19 patients and 3 (8%) of the 37 controls showed a nerve/tendon excursion ratio of .25 or less when tested with the elbow in extension. CONCLUSIONS: Reduced longitudinal excursion of the median nerve at the carpal tunnel was identified in a substantial proportion of patients with CTS. Further studies are merited to determine if reduced median nerve excursion at the carpal tunnel is clinically relevant in CTS, and can be influenced by movement-based interventions.     

感觉神经传导检查比较法在诊断轻度腕管综合征中的应用

目的寻找诊断轻度腕管综合征（CTS）敏感的神经电生理指标。方法回顾性分析经吉林大学第一医院手外科医生临床诊断,并经手术治疗疗效确实,但常规电生理检查提示拇短展肌复合肌肉动作电位的潜伏期（CAMP）及示、中指感觉神经传导检查正常的患者80人,共92例手的腕管综合征患者进行神经电生理分析,采用顺向法记录掌腕正中、尺神经混合神经电位潜伏期时差和环指腕正中、尺神经感觉神经电位潜伏期时差,以潜伏期时差差值≥0．4ms为阳性指标,计算其阳性符合率,并进行统计学分析。结果掌腕正中、尺神经混合神经电位潜伏期时差≥0．4ms为64例,阳性率为69．56％;环指腕正中、尺神经感觉神经电位潜伏期时差≥0．4ms为83例,阳性率为90．21％。其中两种方法均为阳性的62例,均为阴性的7例。结论环指腕正中、尺神经感觉神经电位潜伏期时差在诊断轻度腕管综合征时具有较高的诊断价值。     

Ultrasound elastographic evaluation of the median nerve in hemodialysis with carpal tunnel syndrome

Purpose

The aim of this study was to compare the elasticity of the median nerve (MN) between hemodialysis (HD) patients without carpal tunnel syndrome (CTS) and with CTS, and to evaluate the diagnostic usefulness of the elasticity of the MN in HD-CTS.

Materials and methods

The MN in 22 HD patients without CTS and 49 HD-CTS patients was studied. The cross-sectional area (CSA) and the elasticity of the MN, which was measured as the subcutaneous fat/median nerve (SF/MN) strain ratio, were evaluated.

Results

The mean SF/MN strain ratio in the groups that had received hemodialysis for 0–5, >5–10, and >10–15 years was 1.4 ± 0.28, 1.7 ± 0.18, and 2.0 ± 0.67, respectively. The mean CSA of the MN in the three groups was 9.9 ± 1.30, 11.6 ± 1.61, and 13.4 ± 2.14 mm², respectively. The presence of CTS was predicted by means of SF/MN strain ratio and CSA cutoff values of 1.8 and 11 mm², respectively. Both the SF/MN strain ratio and the CSA in the patients with CTS were higher than those in the patients without CTS (P < 0.05). The sensitivity and specificity of the SF/MN strain ratio and CSA of the MN were 75 and 92 % and 79.2 and 84 %, respectively.

Conclusion

Sonoelastography helps to improve the diagnostic accuracy of the ultrasonographic assessment of CTS.

     

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)     

Palmar conduction time of median and ulnar nerves of normal subjects and patients with carpal tunnel syndrome.

The wrist-palm conduction time for the median and ulnar nerves was determined using antidromic technique in thirty normal subjects. For the median nerve, the conduction time was 1.6 msec. to initial deflection from baseline and 1.7 msec. to peak of the initial negative deflection for the mean plus 2 SD. The median wrist-palm conduction time was then compared to the difference between the median and ulnar wrist-digit conduction times (mean plus 2 SD of 0.5 msec. measured either to initial deflection or peak negative deflection) in order to determine which technique aids more in the electrodiagnosis of patients with a presumptive clinical diagnosis of carpal tunnel syndrome but which normal distal sensory latencies. It was found in ten patients that the results of these two electrodiagnostic methods paralleled each other, and neither appeared more sensitive than the other in establishing the diagnosis.     

"Tethered" median nerve stress test in chronic carpal tunnel syndrome

Tension of the median nerve produced by simultaneous extension of the supinated wrist and distal interphalangeal joint of the index finger was noted to result in proximal volar forearm pain radiation in patients with chronic carpal tunnel syndrome. This sign was less frequent in patients with a more acute syndrome. Adhesions between the median nerve and the overlying transverse carpal ligament and the development of a pseudoneuroma can individually or together occur in the chronic carpal tunnel syndrome limiting distal nerve excursion of the tethered nerve during simultaneous wrist and index finger extension.     

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.