Nerve conduction studies in amyotrophic lateral sclerosis.

Nerve conduction studies (NCS) are an integral part of the evaluation of amyotrophic lateral sclerosis (ALS) patients and are useful in distinguishing ALS from disorders that mimic it. The question often arises whether in the presence of severe atrophy and reduction of the compound muscle action potential amplitude, abnormal conduction velocity (CV), distal latency (DL), or F-wave latency (F) exceeds what can be expected from ALS alone. To determine the limits of abnormality in classic ALS, we prospectively evaluated NCS data from 61 patients who met a strict clinical definition of ALS. We related CV, DL, and F to distal evoked amplitude (AMP) in peroneal (n = 63 observations), median (n = 50), and ulnar (n = 52) nerves. In nerves with reduced AMP, CV rarely fell to less than 80% of the lower limit of normal, and DL and F rarely exceeded 1.25 times the upper limit of normal. Utilizing the entire data set and regression analyses, 95% confidence limits for expected values for CV, F, and DL as a function of AMP were calculated. These limits thus derived suggest criteria for NCS abnormalities in ALS and may be useful in differentiating ALS from other illnesses.     

Nerve conduction studies in natural rubella

Normal nerve conduction velocities and terminal latency values were obtained in 31 patients with natural rubella, many of whom complained of numbness, tingling, and other subjective sensory abnormalities. The observations suggest that true neuropathy may not occur in natural rubella.     

Nerve biopsy and conduction studies in diabetic neuropathy.

Morphological findings in sural nerves were related to nerve conduction in 12 patients with diabetic neuropathy, five with mainly sensory involvement, four with severe, symmetrical sensory-motor polyneuropathy, and three with multiple mononeuropathy. All had loss of large and small myelinated and of unmyelinated fibres, even early in the disease; segmental remyelination was the most prominent myelin alteration in teased fibres, segmental demyelination was found in only a few fibres. Axonal degeneration and Schwann cell damage seem to proceed independently of each other. The relation between recorded conduction velocity and that expected from the diameter of the largest fibres indicated that slowing of 20 to 30% was due to causes other than fibre loss; a grossly diminished conduction velocity was caused mainly by fibre loss. Electrophysiological findings in the sural nerve were largely representative of findings in other nerves, though abnormalities were less marked in the median nerve. In half the endoneurial vessels from diabetic neuropathy the perivascular space was thickened or contained more layers of basal laminae than normal. The same abnormalities were found in one-quarter of the endoneurial vessels from other acquired neuropathies.     

Nerve conduction studies and electromyography in Friedreich's ataxia.

Twenty-six of 50 patients were investigated with nerve conduction studies and electromyography using a standard protocol and were compared to the findings in 50 normal control subjects. Almost all cases of typical Friedreich's ataxia had absent sensory action potentials (SAP) in the digital (92%) or sural (96%) nerves. The others had markedly decreased S.A.P's. In these same patients motor conduction velocities were either normal or only slightly decreased. In the second, atypical group of 9 patients, the motor conduction velocities were considerably decreased. Because of the absence of sensory action potentials in Friedreich's ataxia, and that the absence was noted in our very mild cases, it is proposed that this measure be used to facilitate early diagnosis.     

Nerve conduction and electromyography studies

Nerve conduction studies (NCS) and electromyography (EMG), often shortened to 'EMGs', are a useful adjunct to clinical examination of the peripheral nervous system and striated skeletal muscle. NCS provide an efficient and rapid method of quantifying nerve conduction velocity (CV) and the amplitude of both sensory nerve action potentials (SNAPs) and compound motor action potentials (cMAPs). The CV reflects speed of propagation of action potentials, by saltatory conduction, along large myelinated axons in a peripheral nerve. The amplitude of SNAPs is in part determined by the number of axons in a sensory nerve, whilst amplitude of cMAPs reflects integrated function of the motor axons, neuromuscular junction and striated muscle. Repetitive nerve stimulation (RNS) can identify defects of neuromuscular junction (NMJ) transmission, pre- or post-synaptic. Needle EMG examination can detect myopathic changes in muscle and signs of denervation. Combinations of these procedures can establish if motor and/or sensory nerve cell bodies or peripheral nerves are damaged (e.g. motor neuronopathy, sensory ganglionopathy or neuropathy), and also indicate if the primary target is the axon or the myelin sheath (i.e. axonal or demyelinating neuropathies). The distribution of nerve damage can be determined as either generalised, multifocal (mononeuropathy multiplex) or focal. The latter often due to compression at the common entrapment sites (such as the carpal tunnel, Guyon's canal, cubital tunnel, radial groove, fibular head and tarsal tunnel, to name but a few of the reported hundred or so 'entrapment neuropathies').     

Nerve conduction studies in amyotrophic lateral sclerosis

We studied 137 ulnar nerves and abductor digiti minimi (ADM) muscles in 70 patients with amyotrophic lateral sclerosis (ALS), and correlated the results with ADM strength graded on the Medical Research Council (MRC) scale, to address the potential value of a standardized neurophysiological assessment of this nerve-muscle system. The ulnar nerves of 35 normal subjects matched for age, gender, and height served as controls. Reduced compound muscle action potential (CMAP) amplitude and area in the ADM muscle recordings correlated strongly with weakness. Distal motor latency, proximal conduction time, and F-wave frequency were abnormal with minimally detectable weakness. In weaker ADM muscles, conduction velocities and F-wave latencies were also abnormal. Conduction block was never observed and sensory potentials were normal. An "ALS neurophysiological index" was derived from these ulnar nerve studies and consisted of the expression: (CMAP amplitude/DML) x F frequency -, where F frequency was expressed as the number of F responses recorded in 20 trials. This index was strongly correlated with ADM weakness (r = 0.74, P < 0.001). Neurophysiological studies restricted to a single nerve-muscle system, the ulnar nerve/ADM, appear potentially useful in objectively assessing change in ALS.     

Nerve conduction studies in multiple system atrophy

To study the frequency and severity of peripheral neuropathy in multiple system atrophy (MSA), we performed nerve conduction studies in 42 MSA patients suffering from either cerebellar MSA (MSA-C) or parkinsonian MSA (MSA-P). Abnormal nerve conduction was present in 24% of the patients. Abnormalities were significantly more frequent in MSA-P (43%) compared to MSA-C (14%). Motor nerve conduction velocities were reduced in 4% of the MSA-C and in 7% of the MSA-P patients. Abnormal compound muscle action potentials were more frequent in MSA-P (29% versus 7% in MSA-C) pointing to a more pronounced loss of motor axons in this subgroup. Sensory nerve conduction velocities were abnormal in 4% of the MSA-C and 14% of the MSA-P patients, and mean sensory nerve action potentials were normal in all MSA-C and reduced in 7% of the MSA-P patients. The data provide evidence that the peripheral nervous system is differentially affected in MSA-C and MSA-P.     

Nerve conduction studies in infants and children

The electrophysiologic evaluation of peripheral nerves may provide critically important information, both with respect to diagnosis and prognosis, in the child with a suspected neuromuscular disorder. However, special attention to various technical considerations is necessary to avoid misleading results. Utilizing these techniques, both hereditary and acquired neuropathies may be identified and characterized. The latter has become especially important in view of recent advances in the treatment of acquired demyelinating neuropathies.     

Nerve conduction studies in selected peripheral nerve disorders

PURPOSE OF REVIEW: The physiological properties of nerve and muscle are influenced by pathological changes and the aim of this review is to discuss recent contributions of electrophysiological studies to the understanding and diagnosis of selected peripheral nerve disorders. The relationships between pathology and physiology emphasize the close interdependence between electrophysiological studies, clinical deficits and other laboratory information. Attention should be paid to the strengths and limitations of electrophysiological methods, considering their impact on diagnosis and treatment of patients. RECENT FINDINGS: Several studies have shown particular pathophysiological profiles associated with different antibody subtypes in autoimmune peripheral neuropathies and this association further supports the suggestion of pathological specificity in both acute and chronic neuropathy. The sensitivity and specificity of physiological profiles therefore become increasingly important since some of these neuropathies are accessible to treatment. On the other hand, the pathophysiological and clinical profiles may be heterogeneous in patients with some disorders. This could be related to a more indistinct division between different types of pathology with increased understanding of pathogenetic mechanisms. Moreover, new insights into disturbed axonal function have stimulated attempts to develop methods to explore normal and diseased human nerve function. SUMMARY: The exploration of axonal membrane and ion-channel function has become accessible using studies of excitability and are of potential value where conventional studies only provide nonspecific evidence of the number of fibers and the integrity of myelin. These studies will presumably become increasingly important in the years ahead considering the lack of understanding of the functional disturbances in axonal neuropathies.     

Nerve conduction studies of the sural nerve in childhood

A study of the sural nerve was undertaken to determine latency to onset and peak, duration of action potential, amplitude, and conduction velocity in 33 children, 1 to 7 years old. Multiple tests per patient resulted in 140 measurements per variable. To determine if the interpatient measurement variation was a significant factor compared to the intrapatient differences, one-way analysis of variance was performed. With each variable the F statistic showed the interpatient variation was significantly different (P less than .001) than the intrapatient measurement variation. There was no significant age effect in the latency to onset and peak, the amplitude, and the duration of action potential. The mean value for latency to onset was 2.430 msec, latency to peak 2.997 msec, duration 2.161 msec, and amplitude 8.736 muV. Age was highly significant (P less than .001) with conduction velocities calculated using latency to onset (CV1) and latency to peak (CV2), since distance was less in the younger child, according to the formulas: CV1 = 47.29 + 1.96 (age in years) and CV2 = 38.56 + 1.50 (age in years). Using regression analysis, temperature had no significant effect on CV1 or CV2.     

皮肌炎和多发性肌炎175例神经传导检测

目的 研究皮肌炎(dermatomyositis,DM)和多发性肌炎(polymyositis,PM)合并神经传导检测(NCS)异常患者的临床和电生理特点以及病因探讨.方法 收集2005年1月到2008年9月中国医学科学院北京协和医院病房收治的DM或PM确诊病例175例,对其临床和NCS结果进行回顾性分析.结果 175例患者中,NCS异常者66例,其中明确的周围神经病32例(48.5%),不能肯定为周围神经损害者34例(51.5%).合并周围神经损害的DM或PM患者恶性肿瘤(3/32,9.3%)、其他免疫病(6/32,18.8%)的发生率较无周围神经损害的DM或PM患者(4/109,3.7%;7/109,6.4%)有明显增加(X2=13.653,P=0.003).结论 合并周围神经损害的DM或PM患者恶性肿瘤、其他免疫病的发生率明显增加,NCS可以为临床早期诊断提供更多的提示和帮助.     

肌萎缩侧索硬化患者205例的神经传导特点分析

目的 分析肌萎缩侧索硬化(ALS)患者的神经传导和F波特点,并探讨其与肌力、病程和首发部位等之间的关系.方法 收集于1997年1月至2008年5月期间我院门诊或病房收治的ALS患者205例,均采用常规肌电图检查,测定其运动神经传导、F波以及感觉神经传导(SCV).结果 在205例ALS患者中,仅有3例SCV异常,正中神经、尺神经及胫后神经末端潜伏期(DML)延长者分别占24.9%(48/193)、15.3%(25/163)、21.2%(7/33),复合肌肉动作电位(CMAP)波幅下降者分别占57.0%(110/193)、49.7%(81/163)、39.4%(13/33);68.9%(122/177)患者F波出现率下降,其中31.1%(55/177)F波出现率为0,肌力下降者DML、CMAP波幅及F波出现率改变明显.肢体起病组正中神经CMAP波幅下降[81.5%(53/65)]和F波异常率[70.9%(44/62)出现率下降,45.1%(28/62)出现率为0]较延髓部起病者[32.4%(11/34);F波38.2%(13/34)出现率下降,14.7%(5/34)出现率为0]更明显,两组比较差异有统计学意义(x2=23.629、9.753、9.029,均P<0.01);DML异常两组间差异无统计学意义.Logistic回归分析显示CMAP波幅的降低与上肢远端肌力、首发部位、病程显著相关,F波出现率的降低与上肢远端肌力、首发部位相关.结论 ALS患者可出现DML延长和CMAP波幅降低(后者改变更显著),F波出现率明显下降而传导速度相对正常;DML、CMAP波幅及F波出现率的异常与肌力明显相关.首发部位为肢体和(或)上肢远端肌力下降者CMAP波幅及F波异常率更明显.

Abstract：

Objective To investigate the F-wave and nerve conduction in patients with amyotrophic lateral sclerosis (ALS) and explore the correlation between these parameters and muscle strength, disease duration and onset site.Methods The data of outpatients and inpatients diagnosed with ALS were collected in Peking Union Medical College Hospital from January 1997 to May 2008.Standard sensory and motor nerve conduction study of the median nerve, ulnar nerve and tibial nerve was performed in 205 patients with ALS.F-wave velocity and frequency was measured in median nerve.Parameters for analyses included sensory conduction velocity and amplitude, distal motor latency (DML), and compound muscle action potential (CMAP) amplitude.Correlation between muscle strength and DML, CMAP amplitude or F-wave frequency were also explored.Results Delayed DML of the median nerve, ulnar nerve and tibial nerve were found in 24.9% (48/193), 15.3% (25/163), 21.2% (7/33) of patients respectively.Decreased CMAP amplitudes were found in 57.0% (110/193), 49.7% (81/163), 39.4% (13/33) of patients respectively.Decreased F-wave frequency of the median nerve was found in 68.9% (122/177) of patients.The abnormality of DML,CMAP amplitude and F-wave frequency of median nerve were increased in weaker muscles.Decreased median nerve CMAP amplitude (81.5% (53/65)) and F-wave abnormality (decreased persistence 70.9%(44/62), absent responses 45.1% (28/62)) in spinal onset groups were significantly higher than those in bulbar onset groups (CMAP 32.4% (11/34); F-wave: decreased persistence 38.2% (13/34), absent responses 14.7% (5/34); x2 = 23.629, 9.753, 9.029,all P <0.01).Compared with the bulbar onset group,the abnormality of DML in spinal onset group was higher, but not reach statistical significance.Logistic regression revealed a strong direct association between decreased CMAP amplitudes and upperextremity muscles strength, disease duration and onset symptom.Abnormality of F-wave frequency was associated with upper-extremity muscles strength and onset symptom.Conclusions Delayed DML and decreased amplitude of CMAP are found in ALS patients.CMAP amplitude is a sensitive parameter related to the severity of ALS.F-wave velocity is relatively normal while F-wave frequency of the median nerve is correlated with muscle strength.Decreasing CMAP amplitude and F-wave frequency are correlated strongly with muscle weakening,disease duration and symptom onset over limbs.     

Nerve conduction studies in the superficial radial nerve entrapment syndrome

This report reviews the syndrome of entrapment of the superficial branch of the radial nerve (SBRN) in the forearm, and electrodiagnostic techniques to aid in diagnosis are presented. Normal mean radial sensory conduction in the forearm was found to be 61.4 +/- 3.1 m/sec. Three patients are presented. In two of these comparison of conduction in the SBRN to the lateral antebrachial cutaneous nerve (LACN) and contralateral SBRN was abnormal, whereas the absolute SBRN conduction appeared normal. Normal LACN-SBRN difference in the same arm was 1.9 +/- 1.6 m/sec, with a range of 0-7.0 m/sec; mean SBRN difference in opposite arms of the same subject was 1.8 +/- 1.6 m/sec.     

皮肌炎和多发性肌炎175例神经传导检测

目的 研究皮肌炎(dermatomyositis,DM)和多发性肌炎(polymyositis,PM)合并神经传导检测(NCS)异常患者的临床和电生理特点以及病因探讨.方法 收集2005年1月到2008年9月中国医学科学院北京协和医院病房收治的DM或PM确诊病例175例,对其临床和NCS结果进行回顾性分析.结果 175例患者中,NCS异常者66例,其中明确的周围神经病32例(48.5%),不能肯定为周围神经损害者34例(51.5%).合并周围神经损害的DM或PM患者恶性肿瘤(3/32,9.3%)、其他免疫病(6/32,18.8%)的发生率较无周围神经损害的DM或PM患者(4/109,3.7%;7/109,6.4%)有明显增加(X2=13.653,P=0.003).结论 合并周围神经损害的DM或PM患者恶性肿瘤、其他免疫病的发生率明显增加,NCS可以为临床早期诊断提供更多的提示和帮助.     

Nerve conduction studies in experimental non-freezing cold injury: I. Local nerve cooling.

In rabbits, the tibial nerve was exposed in the lower thigh under general anesthesia and cooled in a metal trough at 1 to 2 degrees C or 5 degrees C for 2, 3, or 4 hours. Nerve conduction studies showed local failure of conduction at the site of cooling which persisted after rewarming, and which was followed by distal degeneration of affected fibers. No persistent conduction block was seen. Changes in maximal velocity indicated that the fastest-conducting motor and afferent axons had been preferentially affected. Histological findings in nerves examined at different intervals after cooling confirmed the physiological evidence of primary axonal damage, affecting particularly large diameter fibers. Paranodal demyelination was inconspicuous and restricted to regions just proximal to sites of axonal degeneration. No segmental demyelination was seen. These results clarify previous uncertainties as to the time-course and distribution of nerve damage after local cooling at temperatures just above freezing point.     

Nerve conduction study in Sydenham's chorea.

Sydenham's chorea (SC) is a late complication of group A beta-hemolytic streptococci infection presumably caused by an abnormal autoimmune reaction. Despite rare case reports of peripheral neuropathy associated with streptococcal infection, there is no investigation of peripheral nerve in SC. We performed nerve conduction studies in a cohort of patients with SC. The neurophysiology investigation comprised measurement of amplitude and sensory conduction velocity of median, ulnar, and sural nerves; amplitude and motor conduction velocity; and F-wave latency of median, ulnar, fibular, and tibial nerves. Twenty-six patients entered the study (12 females, 14 males; mean age 12.8 +/- 3.6 years). Thirteen subjects had absent or decreased deep reflexes. All investigated neurophysiological parameters fell within the normal range for our population. We failed to find neurophysiological evidence of peripheral nerve involvement in patients with a history of SC. Our findings suggest that the possible autoimmune dysfunction in SC patients is not targeted against epitopes present in peripheral nerves.