Electrodiagnostic evidence of subclinical disease states in drug abusers.

One hundred drug abusers, free of clinical signs or symptoms of disease, were examined by electrodiagnostic techniques. Sensory conduction of median, ulnar and sural nerves was evaluated in terms of latency, velocity and amplitude of evoked potential. Motor nerve latencies and conduction velocities of median, ulnar and personeal nerves were determined. Definite changes in the evoked sensory potentials of median and sural nerves of subjects using heroin or LSD were demonstrated. The sensory amplitude changes were suggestive of axonal degreneration because of normal duration. Maximum motor conduction velocity was abnormal in one patient who admitted using a variety of drugs; five heroin and two barbiturate users showed dispersed motor responses suggesting small fiber involvement. No abnormality could be shown in marjuana smokers. Signifcance of these findings is explained, emphasizing important potential for recognition of subclinical abnormalities and the opportunity for disease prevention.     

Sensory palmar stimulation in the diagnosis of carpal tunnel syndrome

The measurement of motor and sensory latencies of the median and ulnar nerves using conventional techniques in able-bodied subjects and patients with a history compatible with carpal tunnel syndrome (CTS) is described. The results obtained by conventional techniques are compared with measurement of median nerve sensory latency obtained by palmar stimulation and the difference of median-ulnar nerve distal sensory latencies. It is concluded that the use of measurement of median palmar sensory latency under the flexor retinaculum adds to the sensitivity of the nerve conduction studies in the diagnosis of CTS. It is suggested that, in patients with suspected CTS in whom conventional nerve conduction studies are normal, other techniques such as the measurement of palmar sensory latency, difference between median and ulnar nerve distal sensory latency and examination of all the digits should be carried out.     

Sural nerve conduction studies and late responses in children undergoing hemodialysis

Physiologic evidence of peripheral neuropathy has been described previously in children undergoing hemodialysis. In order to detect early or subclinical evidence of peripheral neuropathy, several newer electrophysiologic techniques, including latencies of late responses (H reflex and F response) and sural nerve sensory studies, were evaluated in addition to routine motor and sensory conduction in 17 randomly selected children (mean age 14.2 years) undergoing hemodialysis (12 of whom had no clinical evidence of peripheral neuropathy) and 20 age-matched normal control subjects. Conventional motor and sensory conduction studies of median and ulnar nerves and motor conduction of peroneal and tibial nerves showed abnormalities of motor conduction in 5 (29%) and abnormalities of sensory conduction in 2 (12%). Sural nerve sensory potentials were abnormal in 10 (59%) patients. Late response were significantly abnormal in 10 (59%) patients, 5 (29%) of whom had normal routine motor conduction studies in the same nerve distribution. The abnormalities of late responses and motor and sensory conduction were more evident in lower limbs. Studies of late responses and sural sensory conduction provide a method of detecting subclinical neuropathy in this patient population at a time when results of conventional motor and sensory conduction tests are within normal limits. Effects of dialysis may then be followed quantitatively in patients whose neuropathy would otherwise be undetectable.     

Race effect on nerve conduction studies: a comparison between 50 blacks and 50 whites.

OBJECTIVE: To determine whether there are any differences in nerve conduction study results between blacks and whites. DESIGN: The following studies were performed: median, ulnar, peroneal, and tibial motor studies; median and ulnar mixed motor/sensory studies; sural and radial sensory studies; and H-reflex studies. SETTING: Private office or university-based clinic. PARTICIPANTS: Fifty adult blacks and 50 adult whites who met inclusion criteria, recruited through advertisements. MAIN OUTCOME MEASURES: Differences between blacks and whites were compared to determine whether they exceeded a cutoff of 0.2 msec for latencies, 20% difference for amplitudes, 5 m/sec for conduction velocity, and 1.2 msec for H-reflex times. A repeated analysis of variance was performed to detect statistically significant differences (defined as p< or =.01). RESULTS: Only values for the mean peroneal and tibial motor latencies exceeded the cutoff times. The mean peroneal response was faster by 0.3 msec and the mean tibial response was slower by 0.3 msec in blacks than whites. These differences were not statistically significant at a level of p< or =.01. CONCLUSION: There is no significant difference between blacks and whites in normal nerve conduction study findings in healthy adults.     

Effect of interelectrode distance on sural nerve action potential parameters

OBJECTIVE: To assess differences in amplitude, latency, and duration, using a 3-cm vs. 4-cm distance between the active and reference electrodes when performing sural nerve conduction studies (NCS). Current normative data in lower-limb studies are generally based on 3-cm interelectrode differences, although 4-cm differences have been reported to be optimal in the upper limb. DESIGN: Prospective study comparing the onset latency, peak latency, duration, and amplitude for the sural sensory nerve action potential (SNAP) recording at two interelectrode distances in adult volunteers. RESULTS: Forty-three sural nerves were studied in 22 normal subjects. Peak latencies recorded with a 4-cm interelectrode distance were significantly longer than those recorded with a 3-cm distance (mean difference = 0.06 msecs [SD = 0.09, P = 0.0073]). Duration was significantly longer (mean difference = 0.03 msecs [SD = 0.07, P = 0.0270]), conduction velocities were significantly slower (mean difference = -0.7 msecs [SD 1.0, P = 0.0012]), and onset latency and amplitude were not found to differ significantly. Average differences in peak latencies, duration, velocity, onset latency, and amplitude were not correlated with gender, age, or BMI. CONCLUSIONS: In contrast to studies of upper-limb sensory NCS, sural SNAP parameters obtained with 3- and 4-cm interelectrode distances did not differ for onset latencies and amplitude. Peak latencies, duration, and conduction velocity differences, though statistically significant, were of insufficient magnitude to be clinically meaningful. By using a 4-cm instead of a 3-cm interelectrode difference for sural nerve studies, the small prolongation of 0.06 msecs in peak latency and tiny increment of 0.27 muV observed in our investigation is unlikely to influence the electrodiagnostician's interpretation of the study.     

神经传导速度差异规律量化评估肌萎缩侧索硬化症

背景肌电图的神经传导速度异常是肌萎缩侧索硬化( amyotrophic lateral sclerosis,ALS)的诊断标准之一,可否以其变化差异规律来量化患者病情变化和评估预后? 目的研究肌萎缩侧索硬化 (amyotrophic lateral sclerosis,ALS)患者中神经传导速度的改变,建立量化评定肌萎缩侧索硬化病情及其预后的神经生理指数. 设计回顾性分析. 地点和对象本研究的地点为北京大学第三医院神经科,研究对象为北京大学第三医院神经内科 1997-02/1999-03住院患者. 方法对 21名 ALS患者的 30条尺神经、 32条正中神经及 24名健康对照组的 38条尺神经、 40条正中神经进行运动传导速度 (motor conduction velocity, MCV)及感觉传导速度( sensory conduction velocity, SCV)和 F波进行检测.两组间数据进行统计学分析. 主要观察指标两组正中神经神经传导速度与 F波, ALS组患者小指展肌的肌力与 CMAP波幅 /DML× F出现率数值的相关性. 结果 ALS组正中神经、尺神经运动传导速度的远端潜伏期 (distal motor latency, DML)、肌肉动作电位( compound muscle action potential, CMAP)波幅及面积、 F波的出现率较对照组有显著性差异.而两组 MCV、 SCV、 F波的潜伏期差异无显著性. ALS组中 10名小指展肌的肌力与 CMAP波幅 /DML× F出现率的数值有显著的相关性 (r=0.89,P< 0.01). 结论 CMAP波幅 /DML× F波的出现率是一种有效的客观的电生理指数,可对 ALS病情及其预后进行量化评估.     

Effect of Hand Warming on Electrodiagnostic Testing Results and Diagnosis in Patients With Suspected Carpal Tunnel Syndrome

Burnham RS, Burnham TR. Effect of hand warming on electrodiagnostic testing results and diagnosis in patients with suspected carpal tunnel syndrome.

Objectives

To evaluate the effects of hand warming on electrodiagnostic (EDX) parameters of carpal tunnel syndrome (CTS). Specifically, to evaluate the type and magnitude of change in EDX values; to determine whether warming can change the EDX diagnosis of CTS and, if so, to determine whether specific EDX tests are more vulnerable to the effects of warming.

Design

Interventional before-after trial.

Setting

Community EDX laboratory.

Participants

Consecutive patients (N=33) referred for EDX evaluation of suspected CTS.

Intervention

Each upper limb was tested at room temperature (average hand temperature, 31.9°C) and retested after 20 minutes of heating pad warming (average hand temperature, 33.5°C).

Main Outcome Measures

Median and ulnar nerve motor and sensory latency, conduction velocity, and amplitude.

Results

Warming resulted in significantly faster transcarpal tunnel sensory and motor conduction (6%–10%), reduced median: ulnar sensory latency to digit 4 difference (23%), and reduced sensory nerve and compound motor action potential amplitude (10% and 13%, respectively). The changes resulted in 15% fewer limbs meeting the EDX conduction velocity criteria of CTS and 9% fewer by median: ulnar sensory latency to digit 4 difference. Waveform amplitudes became abnormally low after warming in 12% of limbs.

Conclusions

Hand warming using a heating pad for 20 minutes increases median nerve transcarpal tunnel conduction velocity and reduces amplitude. These phenomena introduce potential sources of diagnostic error, particularly in borderline cases. Generally, within hand, between nerve, and within nerve comparison techniques are less susceptible to the conduction velocity effects of warming.     

Compound nerve action potentials from the median and ulnar nerves

The compound nerve action potentials from mixed motor/sensory (MNAP) and sensory (SNAP) nerve stimulation in the median and ulnar nerves were recorded in both arms of 20 able-bodied subjects. Intranerve and internerve peak-to-peak amplitudes were compared. An SNAP/MNAP amplitude ratio greater than 0.25 exceeded the mean by 2SD. The fastest, intermediate, and slowest conduction velocities were calculated from chosen points on the biphasic waveform. An intermediate MNAP conduction velocity for the median and ulnar nerves of less than 49.5m/sec exceeded more than 2SD below the mean. Likewise, an intermediate SNAP conduction velocity of less than 45.5m/sec exceeded 2SD below the mean. Median MNAP latency across the carpal tunnel was 1.0 +/- 0.3 and ulnar MNAP conduction velocity across the elbow was 59.7 +/- 3.8m/sec. This technique may supplement traditional electrodiagnostic studies in evaluating upper extremity neuropathies.     

腕尺管综合征肌电图检测分析

目的探讨腕尺管综合征的肌电图表现。方法对13例腕尺管综合征患者行肌电图检测,包括尺神经运动潜伏期、运动波幅、尺神经小指感觉传导速度、感觉波幅等,与其健侧对照比较,评估肌电图表现差异。结果腕尺管综合征患者其患侧肌电图与健侧比较,尺神经运动潜伏期延长(P<0.01),运动波幅缩小(P<0.01),尺神经小指感觉传导速度减慢(P<0.01)、感觉波幅缩小(P<0.01),小指展肌、第Ⅰ骨间肌肌电图也出现静息状态及重收缩状态的改变。结论腕尺管综合征患者存在肌电图的多项改变,早期检测对于其诊断及其治疗具有重要意义。     

Electrodiagnosis of mild carpal tunnel syndrome

Electrophysiologic tests have been reported to detect mild carpal tunnel syndrome (CTS). Such tests include (i) absolute palmar latency of median wrist segment; (ii) comparison of median and radial distal sensory latencies in digit I; (iii) comparison of median and ulnar distal sensory latencies in digit IV; (iv) comparison of median and ulnar palmar latencies; (v) comparison of median and ulnar sensory potential amplitudes in digits II and V. To clarify the clinical utility of these tests, the parameters of all five tests were determined across four carefully established patient subgroups: group A, controls; group B, CTS referrals with normal nerve conduction studies (NCS) and normal needle electromyography (EMG); group C, CTS referrals with abnormal NCS and normal EMG; group D, CTS referrals with abnormal NCS and abnormal EMG. Special attention was focused on patients in group B who represent the diagnostic dilemma. In group B, tests ii and iii each yielded abnormal results in 44% of hands, while the combination of tests ii and iii yielded abnormal results in 51% of hands.     

腕管综合征的电生理分析及与身体质量指数的相关性

目的:探讨88例腕管综合征(CTS)的电生理特点,明确电生理检查的诊断价值。方法:对88例门诊腕管综合征患者行一侧或双侧正中神经、尺神经的分段运动神经传导速度(MCV)和,Ⅰ、Ⅴ、Ⅳ指刺激感觉神经传导速度(SCV)测定,以及拇短展肌针极肌电图检查;计算每一位患者身体质量指数(BMI)及正中神经与尺神经Ⅳ指刺激感觉神经动作电位(SNAP)波幅比值。结果:Ⅰ、Ⅳ指刺激正中神经SNAP潜伏期延长者的百分比分别为59.1%与65.9%;复合肌肉动作电位(CMAP)波幅降低者中拇短展肌肌电图异常者占87.2%;SNAP各参数正常者中有8例(72.7%)出现Ⅳ指刺激正中神经与尺神经波幅比值的异常,各异常参数患者BMI值无显著性差异。结论:神经电生理检查是诊断CTS的理想检测手段。     

80例腕管综合征患者的神经电生理测定

目的：观察神经电生理检测对腕管综合征(CTS)的诊断敏感性。方法：80例临床提示为CTS或不能除外CTS的患者进行神经电生理测定并进行回顾性分析。结果：80例116侧正中神经复合肌肉动作电位末端运动潜伏期和波幅、肘至腕的运动传导速度、指至腕部的感觉传导速度及感觉神经动作电位波幅等5项指标检测异常率分别为75．0％、19．8％、9．5％、88．8％及37．9％；45例65侧拇指正中／桡浅神经潜伏期差(MRLD)及环指正中／尺神经潜伏期差(MULD)检测异常率95．4％。结论：正中神经拇指至腕段的感觉传导速度测定是诊断CTS的敏感指标，采用MRLD及MULD测定，诊断敏感性更高。     

Repeatability of Nerve conduction Measurements using Automation

Objective

To quantify nerve conduction study (NCS) reproducibility utilizing an automated NCS system (NC-stat^®, NeuroMetrix, Inc.).

Method

Healthy volunteers without neuropathic symptoms participated in the study. Their median, ulnar, peroneal, and tibial nerves were tested twice (7 days apart) by the same technician with an NC-stat^® instrument. Pre-fabricated electrode arrays specific to each nerve were used. Both motor responses (compound motor action potential [CMAP] and F-waves –all nerves) and sensory responses (sensory nerve action potentials [SNAP] –median and ulnar nerves only) were recorded following supramaximal stimuli. Automated algorithms determined all NCS parameters: distal motor latency (DML), mean F-wave latency (FWL), distal sensory latency (DSL), CMAP amplitude, and SNAP amplitude. Latency was adjusted for skin temperature deviation from reference. Pearson correlation coefficient (CC), intraclass correlation coefficient (ICC), coefficient of variance (CoV), and relative intertrial variation (RIV) were calculated.

Results

Fifteen subjects participated in either upper or lower extremity studies with nine participating in both. With the exception of CMAP amplitude, all parameters had CoV less than 0.06. Upper extremity amplitude parameters had CCs greater than 0.85. CCs for latencies were greater than 0.80 except for the median nerve FWL (CC = 0.69). For lower extremity nerves, ICCs were highest for mean FWL (>0.90), followed by DML (>0.82) and then CMAP (peroneal 0.33, tibial 0.73). The 10th to 90th RIV percentiles were bounded by ±7% for F-wave latencies;?±9% for all DSLs; and?±11% for DML (except peroneal at 15%).

Conclusions

The reproducibility of NCS parameters obtained with an automated NCS instrument compared favorably with traditional electromyography laboratories. F-wave latencies had the highest repeatability, followed by DML, DSL, SNAP and CMAP amplitude. Given their high reproducibility, automated NCS instrument may encourage wider utilization of NCS in clinical and research applications.     

Physical activity: its influence on nerve conduction velocity

In a group of 40 healthy subjects, distal and proximal latencies of the median, tibial, and peroneal motor, and sural sensory nerves and their respective skin surface temperatures (Tsk) were measured before and after walking or bicycling. The baseline tests were performed 30 minutes after resting in a constant room temperature of 24C. The ambulation or bicycling task was continued for 30 minutes at a constant rate. Postactivity tests were performed within 30 minutes and between 45 to 60 minutes after termination of activity. Another test was done 75 to 90 minutes after bicycle exercise. After walking, there was a significant increase in Tsk in all lower extremity nerves tested (p less than 0.01). The increases were accompanied by faster distal and proximal latencies in both testing periods (p less than 0.01). Median nerve Tsk, distal and proximal latencies did not differ significantly from baseline values initially, but 45 minutes after walking Tsk was elevated and proximal latency had become faster (p less than 0.01). Following bicycling, lower extremity Tsk was significantly reduced over tibial, peroneal, and sural nerves by the third testing period (p less than 0.01) but only sural latencies were significantly prolonged (p less than 0.05) by this time. In the upper extremities median Tsk was significantly elevated and distal latency had become significantly faster 45 minutes after bicycling. Our data suggest that activity significantly influences nerve conduction latency results due to tissue temperature alteration. In addition, 30 minutes of rest after activity may not be sufficient time for the lower extremity temperatures to become stable.     

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。     

正中神经压迫试验对腕管综合征神经传导速度的影响

目的比较正中神经压迫试验对腕管综合征（carpal tunnel syndrome,CTS）患者正中神经传导速度的影响。方法设置CTS组和对照组两个组别,共29例受试者纳入研究。CTS组为14例CTS患者,对照组为15例健康受试者。神经传导速度测定包括正中神经和尺神经的感觉传导末端潜伏期（distal sensory latency,DSL）、感觉神经动作电位（sensory nerve action potential,SNAP）、跨腕关节感觉传导速度（sensory conduction velocity,SCV）、运动传导末端潜伏期（distal motor latency,DML）及复合肌肉动作电位（compound muscle action potential,CMAP）。先测感觉传导,再测运动传导。正中神经压迫试验5min后再次测量上述指标。结果正中神经压迫试验前后电生理检查考虑诊断CTS分别为22侧和24侧。压迫正中神经后,CTS组正中神经DSL较压迫前显著延长（P〈0.05）。CTS组尺神经和对照组正中神经及尺神经的各参数在压迫前后均无显著改变（P〉0.05）。与对照组相比,在压迫试验前后CTS组的正中神经DSL和DML均明显延长（P〈0.05）,尺神经DSL和DML均无显著改变（P〉0.05）。结论正中神经压迫试验5min能使CTS患者正中神经的感觉传导末端潜伏时明显延长,有助于提高神经传导测定对早期CTS的诊断率。     

Electrophysiologic responses of human sural nerve to temperature

The purpose of this study was to assess the conduction, specifically the latency and amplitude of the sensory nerve action potential (SNAP), of the sural nerve as a function of intraneural temperature of the leg. The electrophysiologic responses of the sural nerve were determined at different temperatures in 22 healthy adults. Distal sensory latency and amplitude of the sural SNAP was determined at 1 degree C intervals over a limb temperature range of 23 degrees to 40 degrees C. Limb temperature was monitored with a thermistor probe placed subcutaneously near the sural nerve. Ice bath soaks were used for cooling and infrared radiation for warming the limbs. An analysis of covariance was performed for the SNAP latencies and amplitudes to determine the effect of gender and leg (right or left) at each temperature level. No effect of gender or leg on neural conduction was detected in individual subjects. A regression analysis was then used on pooled data to determine the effect of temperature on sural SNAP latency and amplitude. An inverse linear change in the latency of sural SNAP was observed over the temperature ranges used. Mean latency increased 0.1 msec per 1 degree C increase in subcutaneous temperature. A direct relationship between amplitude of the SNAP and temperature was determined. Mean amplitude increased 0.3 muV per 1 degree C increase in subcutaneous temperature. The results of this study support previous reports, which state that SNAP latency is indirectly related to the intraneural temperature. Clinical electromyographers must monitor the temperature of the lower leg and foot whenever sensorineural conduction of the lower limbs is performed.     

Ulnar nerve involvement in carpal tunnel syndrome

This is a retrospective study of the involvement of the ulnar nerve in patients with electrodiagnostic evidence of carpal tunnel syndrome as defined by median sensory nerve action potential (SNAP) greater than 3.6msec at the wrist and/or motor distal latency in excess of 4.3msec. The study included 248 patients, 63 (25%) with unilateral and 185 (75%) with bilateral carpal tunnel syndrome. The electrodiagnostic criteria for ulnar nerve involvement was a SNAP peak latency greater than 3.7msec and/or motor distal latency in excess of 4.2msec. One hundred fourteen patients (46%) had delayed ulnar SNAP peak at the wrist; of these, 100 cases had bilateral ulnar nerve involvement and 14 had unilateral abnormalities. Slowing of the motor nerve conduction velocity for the elbow-wrist segment was noted in 24% and 15% of the study group for the median and ulnar nerves, respectively. An incidental finding was the presence of "double crush syndrome" in 35 patients (14%). The results of this study suggest the frequent association of ulnar nerve involvement at the wrist for sensory fibers and 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.     

The pronator syndrome. An evaluation of dynamic maneuvers for improving electrodiagnostic sensitivity

The role of three test maneuvers (elbow flexion, forearm pronation and finger flexion against resistance) in improving sensitivity of conventional nerve conduction studies used in cases of suspected pronator teres syndrome were evaluated in 11 healthy control subjects and 10 patients with the clinical diagnosis of pronator teres syndrome. Stimulation of the median nerve was performed above and below the elbow before exercise and immediately after the test maneuvers; the resultant median motor and sensory responses were recorded. Before and after exercise, median motor and sensory responses (e.g., amplitude, latency, velocity) did not differ significantly between the two groups; only one patient with suspected pronator teres syndrome developed sensory amplitude changes after exercise. We concluded that these test maneuvers did not significantly improve the sensitivity of conventional nerve conduction studies in the diagnosis of pronator teres syndrome.