Larger muscle mass of the upper limb correlates with lower amplitudes of deltoid MEPs following transcranial stimulation

To perform spinal surgery safely, it is important to understand the risk factors, including factors that negatively influence intraoperative neuromonitoring (IONM). Transcranial motor evoked potentials (TcMEPs) are important in IONM. Therefore, we aimed to investigate whether muscle mass affects the waveforms of TcMEPs to understand the risk factors influencing TcMEPs. We enrolled 48 patients with thoracolumbar spinal diseases who underwent surgery at our facility between April 2015 and March 2018. Before surgery, the body composition, including muscle mass and fat mass, of all patients was measured using bioelectrical impedance analysis (BIA). During surgery, cranial stimulation under general anesthesia was used to derive TcMEPs, enabling us to measure the amplitude, using the control wave of the TcMEPs of the deltoid muscles and the abductor digiti minimi (ADM) muscles. We found a negative correlation between the amplitude of deltoid-muscle TcMEPs and muscle mass of the upper limb. The amplitude of deltoid-muscle TcMEPs did not correlate with the skeletal muscle index (SMI), muscle mass of the lower limb, or body fat mass. The amplitude of ADM-muscle TcMEPs did not correlate with SMI, muscle mass of any limb, or body fat mass. In conclusion, a larger muscle mass of the upper limb correlated with a lower amplitude of deltoid-muscle TcMEPs. By contrast, there was no correlation between the muscle mass of the upper limb and the amplitude of ADM-muscle TcMEPs. These findings suggest that TcMEPs of the ADM are less influenced by muscle mass and are more stable than those of the deltoid.     

低钾型周期性瘫痪患者运动诱发试验中肌力和肌电图改变与血钾的关系

目的 通过长时运动诱发试验,观察低钾型周期性瘫痪患者肌力和肌电图的变化与血钾之间的关系.方法 收集确诊为低钾型周期性瘫痪患者78例,对小指展肌进行运动诱发试验测定,以拇短展肌作为对照,观察120 min,测定运动诱发前后尺神经/小指展肌和正中神经/拇短展肌复合肌肉动作电位(compound muscle action potential,CMAP)波幅变化,同时观察患者小指外展和小指内收肌力以及拇短展肌肌力的变化,部分患者测定运动前后血钾水平.分析运动后不同肌肉的肌力、CMAP波幅与血钾之间的关系.结果 在小指外展运动后,78例患者尺神经CMAP波幅运动后比运动前明显下降,分别为(4.6±2.7)、(9.6±3.2)mV(t=16.047,P=0.000),而正中神经CMAP波幅在小指外展运动后与运动前相比无明显差异,分别为(10.9±4.2)、(11.2±3.9)mV(t=0.673,P=0.822).在运动后,76例小指外展肌力下降;有41例小指外展肌力小于Ⅲ级,但同侧小指内收和拇短展肌肌力仍为V级,对其中10例患者在运动前和运动后测定血钾,结果无明显差异,分别为(3.8±0.3)、(3.9±0.4)mmol/L(t =0.395,P=0.702).结论 在低钾型周期性瘫痪患者进行运动诱发试验时,血钾并非影响肌力和CMAP波幅变化的关键因素.     

Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer

OBJECTIVES: To determine the prognosis in patients with Lambert-Eaton myasthenic syndrome (LEMS) without small cell lung cancer (SCLC), and to analyse longitudinal clinical, electrophysiological, and immunological data on each patient to establish prognostic factors for long term outcome. METHODS: The retrospective and part prospective study of 47 patients with LEMS was undertaken from data recorded during visits to a specialist neuromuscular clinic. Serial measurements of muscle strength score in shoulder abduction, elbow extension and hip flexion, compound muscle action potential (CMAP) amplitude, and postcontraction increment in abductor digiti minimi (ADM), and anti-P/Q-type voltage gated calcium channel (VGCC) antibody titre were made at each visit. RESULTS: Muscle strength scores were improved in 88% of patients after a median duration of immunosuppressive treatment of 6 years (range 1.3 to 17 years); anti-VGCC antibody titres fell in 52% after treatment; and mean resting CMAP amplitude improved from 2.7 mV initially to 8.8 mV after 2 years of treatment p<0.001). Initial pretreatment anti-VGCC antibody titre did not correlate significantly with either CMAP amplitude, CMAP increment, or clinical score: from serial measurements made during follow up, significant correlation between antibody titre and CMAP amplitude was seen in only two patients. Sustained clinical remission was achieved by 20 (43%) of whom only four remained in remission without the need for immunosuppression. Using a Cox proportional hazards model, the only independent predictor of sustained clinical remission was initial pretreatment clinical score (p=0.03). Lymphoma presented in three patients during the study. CONCLUSIONS: The prognosis in patients with LEMS without SCLC is favourable, although patients often need significant doses of immunosuppressive treatment to remain clinically stable. Only initial clinical muscle strength measurements and not anti-VGCC antibody titres or electrophysiological recordings are predictive of long term outcome.     

REPETITIVE PHRENIC NERVE STIMULATION: USEFULNESS IN DIAGNOSTIC WORK-UP OF MIASTENIA GRAVIS (MG)

Cocito D., Isoardo G., Ciaramitaro P., Proto G., Testa M., Durelli L., Bergamasco B.
Dipartimento di Neuroscienze, Università di Torino
OBJECT : To evaluate sensitivity and specificity of repetitive nerve stimulation on diaphragm muscle stimulating phrenic nerve (RNS-DIAP) for diagnosis of MG, in comparison with RNS on abductor digiti minimi stimulating ulnar nerve (RNS-ADM) and on deltoid muscle stimulating axillary nerve (RNS-DELT). PATIENTS AND METHODS : We performed RNS-DIAP, RNS-DELT and RNS-ADM in 12 MG patients (9 women, 3 men, mean age: 55 ± 19 years) and 12 healthy controls (4 women, 8 men, mean age: 33 ± 14). RESULTS : Only 2 of 12 MG patients had positive RNS-ADM (-10% change in M-response area at fifth response), 11 had positive RNS-DELT and 12 had positive RNS-DIAP. Mean decrease in CMAP area was 8 ± 9% in RNS-ADM, 27 ± 13% in RNS-DELT and 31 ± 10% in RNS-DIAP. Difference between decrease in CMAP area was significant only between RNS-DIAP and RNS-ADM (p=0.002) and between RNS-DELT and RNS-ADM (p=0.0003). There was a weak correlation between clinical MG score and decrease in CMAP area in RNS-DIAP, however, 3 of 12 positive patients developed respiratory failure a few days after the test. DISCUSSION : In our hands, RNS-DIAP has no significant advantage as compared to RNSW-DELT in terms of sensitivity and specificity for MG diagnosis. Furthermore, this test was not well tolerated by the vast majority of patients.     

肌萎缩侧索硬化患者膈神经传导的电生理分析

目的 通过分析肌萎缩侧索硬化(Amyotrophic Lateral Sclerosis,ALS)患者膈神经传导检测,并结合其它神经电生理资料,为该病提供更深入的认识,进一步指导临床诊疗。方法 研究范围为武汉大学人民医院2014年1月-2021年12月就诊的ALS患者共88例,收集患者的一般资料、主要症状及体征、肌萎缩侧索硬化改良量表(ALSFRS-R)评分、运动神经传导检测中的复合肌肉动作电位(CMAP)波幅和远端运动潜伏期(DML)等指标。结果(1)运动神经传导检测中CMAP波幅降低192条(43.6%),膈神经波幅异常率为35.2%; 远端潜伏期延长116条(26.4%),膈神经DML异常率为77.3%;(2)膈神经DML在性别方面存在明显差异(P<0.01);(3)ALSFRS-R评分与膈神经、尺神经、正中神经、腓总神经、胫神经的CMAP波幅呈正相关(r=0.393,P<0.01; r=0.375,P<0.01; r=0.413,P<0.01; r=0.251,P<0.05; r=0.442,P<0.01);(4)膈神经DML及CMAP波幅在起病部位方面存在明显差异(P<0.05; P<0.05);(5)膈神经DML在判断病情中度和轻度之间的最佳界点为9.095 ms,敏感性为85.7%,特异性为80.2%。结论 ALS患者的运动神经传导可表现异常,CMAP波幅下降占比较大,但膈神经中潜伏期延长比CMAP波幅降低更多见。膈神经传导检测存在一定程度的性别差异。行运动神经传导检测时多条神经CMAP波幅变化可反映ALS患者病情严重程度。膈神经潜伏期变化可更敏感地反映ALS的病情严重程度,以期指导临床诊断与治疗。     

Character of diaphragm compound muscle action potential and phrenic nerve conduction time in patients with obstructive sleep apnea-hypopnea syndrome☆◇

BACKGROUND： Both hypoxia and.carbon dioxide retention can damage phrenic nerve and muscle conduction, as well as diaphragm function. Diaphragm compound muscle action potential and phrenic nerve conduction time are reliable indicators for measuring phrenic nerve and diaphragm function. OBJECTIVES： To verify the hypothesis that changes of phrenic nerve conduction time （PNCT） and diaphragm compound muscle action potential （CMAP） in obstructive sleep apnea-hypopnea syndrome （OSAHS） patients might contribute to the decline of phrenic nerve and diaphragm function. PNCT and CMAP were measured with multipair esophageal electrodes combined with unilateral magnetic stimulation. DESIGN, TIME AND SETTING： Case controlled study. The experiment was carried out in Guangzhou Institute of Respiratory Disease, Guangzhou MediCal College, from June 2005 to April 2006. PARTICIPANTS： Twenty seven OSAHS patients and eight primary snoring subjects from Guangzhou Institute of Respiratory Disease, Guangzhou Medical College were recruited and all subjects were diagnosed by polysomnography （PSG）. Sixteen healthy, non-snoring subjects in the hospital for medical examination during the same time period were selected as the control group. METHODS： Esophageal electrodes, made by Guangzhou Institute of Respiratory Disease, combined with unilateral magnetic stimulation, were used to measure PNCT and CMAP of all subjects. PNCT was defined as the time from stimulation artifact to the onset of CMAP and diaphragm CMAP amplitude was measured from peak to peak. Oxygen desaturation index and apnea-hypopnea index were measured using PSG, and their relevance to PNCT and CMAP were analyzed. PNCT and CMAP in five OSAHS patients were repeatedly measured after effective nasal continuous positive airway pressure treatment for more than 2 months. MAIN OUTCOME MEASURES： （1） PNCT and diaphragm CMAP of subjects in each group. （2） Relevance of oxygen desaturation index and apnea-hypopnea index to PNCT and CMAP. （3） Changes of     

Quantitative assessment of motor impairment and surgical outcome in Hirayama disease with proximal involvement using motor unit number index

ObjectiveTo assess the feasibility of motor unit number index (MUNIX) in quantitatively evaluating Hirayama disease (HD) with proximal involvement and to identify the effectiveness of anterior cervical fusion (ACF) in treating atypical HD with proximal involvement.MethodsThis study included 28 atypical HD patients with proximal involvement (proximal-distal vs. distal-proximal groups: 5 vs. 23) and 41 healthy controls. All patients underwent pre- and postoperative 1-year MUNIX tests on abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB) and deltoid (Del). The disabilities of arm, shoulder and hand (DASH) and Medical Research Council (MRC) scales were also performed in these patients before and one year after operation.ResultsPreoperatively, the patients in the distal-proximal group showed reduced compound muscle action potential (CMAP), decreased MUNIX and increased motor unit size index (MUSIX) in bilateral distal muscles and symptomatic-side proximal muscles (P < 0.05), and similar abnormalities were also observed in ADM, BB and Del on the symptomatic side in the proximal-distal groups (P < 0.05). Postoperative follow-up analysis identified increased MUNIX in the symptomatic-side proximal muscles with improved motor function in the proximal-distal groups (P < 0.05), and distal-proximal group patients showed an increase in both CMAP and MUSIX in the symptomatic-side proximal muscles (P < 0.05).ConclusionsMUNIX may serve as an available supplementary test to quantitatively evaluate the motor dysfunction and treatment outcome in HD with proximal involvement. ACF procedures can effectively treat these atypical HD patients, especially for those whose symptoms started in proximal muscles.     

Character of diaphragm compound muscle action potential and phrenic nerve conduction time in patients with obstructive sleep apnea-hypopnea syndrome

BACKGROUND: Both hypoxia and carbon dioxide retention can damage phrenic nerve and muscle conduction, as well as diaphragm function. Diaphragm compound muscle action potential and phrenic nerve conduction time are reliable indicators for measuring phrenic nerve and diaphragm function.OBJECTIVES: To verify the hypothesis that changes of phrenic nerve conduction time (PNCT) and diaphragm compound muscle action potential (CMAP) in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients might contribute to the decline of phrenic nerve and diaphragm function. PNCT and CMAP were measured with multipair esophageal electrodes combined with unilateral magnetic stimulation.DESIGN, TIME AND SETTING: Case controlled study. The experiment was carried out in Guangzhou Institute of Respiratory Disease, Guangzhou Medical College, from June 2005 to April 2006.PARTICIPANTS: Twenty seven OSAHS patients and eight primary snoring subjects from Guangzhou Institute of Respiratory Disease, Guangzhou Medical College were recruited and all subjects were diagnosed by polysomnography (PSG). Sixteen healthy, non-snoring subjects in the hospital for medical examination during the same time period were selected as the control group.METHODS: Esophageal electrodes, made by Guangzhou Institute of Respiratory Disease, combined with unilateral magnetic stimulation, were used to measure PNCT and CMAP of all subjects. PNCT was defined as the time from stimulation artifact to the onset of CMAP and diaphragm CMAP amplitude was measured from peak to peak. Oxygen desaturation index and apnea-hypopnea index were measured using PSG, and their relevance to PNCT and CMAP were analyzed. PNCT and CMAP in five OSAHS patients were repeatedly measured after effective nasal continuous positive airway pressure treatment for more than 2 months.MAIN OUTCOME MEAAURES: (1) PNCT and diaphragm CMAP of suhjects in each group. (2) Relevance of oxygen desaturation index and apnea-hypopnea index to PNCT and CMAP. (3) Changes of PNCT and CMAP of OSAHS patients before and after treatment.RESULTS: All subjects were included in the analyzed results. (1) PNCT of the OSAHS group was significantly longer compared to that of the control and primary snore groups, while CMAP of the OSAHS group was significantly lower (P<0.05). (2) PNCT and CMAP recorded from both sides correlated significantly with oxygen desaturation index and with apnea-hypopnea index (P<0.01). (3) PNCT shortened signiticantly after effective nasal continuous positive airway pressure treatment for more than 2 months (P<0.05).CONCLUSION: Prolongation of PNCT and decrease of CMAP might contribute to the decline of phrenic nerve and diaphragm function caused by repeated nocturnal hypoxia and carbon dioxide retention. The impairment of the phrenic nerve might also decrease diaphragm function.     

临床运动诱发试验在低钾型周期性瘫痪诊断中的价值

目的 通过观察运动诱发试验后小指外展幅度和肌电图复合肌肉动作电位(compound muscle action potential,CMAP)变化的特点,建立一种在非发作期诊断低钾型周期性瘫痪的新方法.方法 收集确诊为低钾型周期性瘫痪的患者59例,以非周期性瘫痪患者38例作为对照,对小指展肌进行运动诱发试验测定(低钾型周期性瘫痪患者选择发作间期),观察120 min,测定运动诱发前后肌电图CMAP波幅变化的百分比,同时观察小指展肌肌力的变化以及小指外展幅度的变化.结果 在运动结束后120 min,患者组和对照组CMAP波幅下降的百分比[M50(M25,M75)]分别为54.1%(43.1%,66.3%)和11.1%(2.0%,21.3%),差异有统计学意义(Z=6.731,P=0.000);小指外展幅度下降百分比[M50(M25,M75)]分别为39.4%(26.3%,48.9%)和7.8%(1.3%,13.7%),差异有统计学意义(Z=5.519,P=0.000).运动后小指展肌肌力小于Ⅳ级者在两组分别为96.3%(52/54)和8.6%(3/35,x2=69.2,P=0.000).当采用小指外展幅度下降百分比＞20%作为界值时,诊断周期性瘫痪的敏感度为87.5%,特异度为90.5%.结论 临床运动诱发试验有助于低钾型周期性瘫痪的诊断.     

平山病患者的临床、肌电图和磁共振研究

目的探讨平山病(HD)患者的临床表现、肌电图和磁共振(MRI)特点。方法收集2009-05-2012-02收治的HD患者的人口学资料、临床表现、电生理和颈椎MRI表现,并进行分析。另设年龄、性别匹配的健康对照组进行电生理检查。结果 (1)HD患者共25例,均为男性,年龄15～24岁,平均年龄(17.64±2.20)岁。临床表现局限于单侧者22例,其中右侧15例、左侧7例;双侧者3例。手或/和前臂肌肉萎缩25例,冷麻痹13例,手指震颤5例。(2)有临床表现侧小指展肌和拇短展肌肌肉电位波幅均减低,且二者波幅比值减小。(3)异常自发活动出现率在第一骨间肌和小指展肌100%、拇短伸肌89.3%、拇短展肌85.7%;在单侧有临床表现的22例中,11例(50%)患者的无症状侧显示异常自发活动。(4)完成MRI扫描的14例中,自然位均显示第2～7颈椎体后方下缘连线与椎体相交、下段颈髓萎缩变扁平;屈曲位时硬膜腔后壁前移7例。结论 HD多见于男性,以右侧多发。结合临床、肌电图以及影像学表现,有助于临床更全面认识HD。     

Reply to Spielholz

In this study we describe the electrophysiological findings in botulism patients with neuromuscular respiratory failure from major botulism outbreaks in Thailand. High‐rate repetitive nerve stimulation testing (RNST) of the abductor digiti minimi (ADM) muscle of 17 botulism patients with neuromuscular respiratory failure showed mostly incremental responses, especially in response to >20‐HZ stimulation. In the most severe stage of neuromuscular respiratory failure, RNST failed to elicit a compound muscle action potential (CMAP) of the ADM muscle. In the moderately severe stage, the initial CMAPs were of very low amplitude, and a 3‐HZ RNST elicited incremental or decremental responses. A 10‐HZ RNST elicited mainly decremental responses. In the early recovery stage, the initial CMAP amplitudes of the ADM muscle improved, with initially low amplitudes and an incremental response to 3‐ and 10‐HZ RNSTs. Improved electrophysiological patterns of the ADM muscle correlated with improved respiratory muscle function. Incremental responses to 20‐HZ RNST were most useful for diagnosis. The initial electrodiagnostic sign of recovery following treatment of neuromuscular respiratory failure was an increased CMAP amplitude and an incremental response to 10–20‐HZ RNST. Muscle Nerve 40: 271–278, 2009     

Visualization of the diaphragm muscle with ultrasound improves diagnostic accuracy of phrenic nerve conduction studies

Introduction: Evaluation of phrenic neuropathy (PN) with phrenic nerve conduction studies (PNCS) is associated with false negatives. Visualization of diaphragmatic muscle twitch with diaphragm ultrasound (DUS) when performing PNCS may help to solve this problem. Methods: We performed bilateral, simultaneous DUS–PNCS in 10 healthy adults and 12 patients with PN. The amplitude of the diaphragm compound muscle action potential (CMAP) (on PNCS) and twitch (on DUS) was calculated. Results: Control subjects had <38% side‐to‐side asymmetry in twitch amplitude (on DUS) and 53% asymmetry in phrenic CMAP (on PCNS). In the 12 patients with PN, 12 phrenic neuropathies were detected. Three of these patients had either significant side‐to‐side asymmetry or absolute reduction in diaphragm movement that was not detected with PNCS. There were no cases in which the PNCS showed an abnormality but the DUS did not. Conclusions: The addition of DUS to PNCS enhances diagnostic accuracy in PN. Muscle Nerve 49 : 669–675, 2014     

Significant CMAP decrement by repetitive nerve stimulation is more frequent in median than ulnar nerves of patients with amyotrophic lateral sclerosis

Introduction: Several studies have shown a significant amplitude decrement in compound muscle action potentials (CMAPs) on repetitive nerve stimulation (RNS) of muscles involved in amyotrophic lateral sclerosis (ALS).In ALS, muscle wasting preferentially affects the thenar muscles (APB) rather than the hypothenar muscles (ADM). Methods: We performed RNS studies in the APB and ADM muscles of 32 ALS patients to determine whether the effect of RNS differs between the median and ulnar nerves. Results: The decremental responses to RNS were greater in the APB than in the ADM. Reduced CMAP amplitude was negatively correlated with CMAP decrement in median but not in ulnar nerves. Conclusions: The greater CMAP decrement in median nerve is attributable to preferential involvement of the APB in the pathophysiology of ALS or some underlying difference in the biology of the two muscles/nerves. Further investigations will better our understanding of the pathophysiology of ALS. Muscle Nerve, 2012     

Clinical and electrophysiological aspects of distal ulnar neuropathy

OBJECTIVES: To evaluate the use of fixed distance side to side comparison of abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) studies in the diagnosis of distal ulnar neuropathy. MATERIALS AND METHODS: Thirty normal controls underwent ADM and FDI CMAP studies bilaterally at a fixed ADM recording to stimulating point distance of 6 cm. Side to side mean latency differences to both muscles were calculated. Twenty patients with suspected unilateral distal ulnar neuropathy from routine nerve conduction studies had positive results when compared with controls. RESULTS: The upper limit of normal for side to side mean latency difference at 3 SD above the mean was 0.394 and 0.474 ms for ADM and FDI, respectively. All 20 patients had side to side mean CMAP latency difference above 3 SDs in the ADM, FDI or both muscles. Fifty percent of cases had involvement of the superficial sensory branch. CONCLUSIONS: Fixed distance side to side CMAP latency comparison is a useful electrodiagnostic adjunct for distal ulnar neuropathy. Trauma was the most common aetiology in the 20 reported cases. Correlation was found between aetiological factors and sites of lesions as localized with this method.     

Pattern difference of dissociated hand muscle atrophy in amyotrophic lateral sclerosis and variants

Introduction: Split hand is considered to be a specific feature of amyotrophic lateral sclerosis (ALS). Methods: We evaluated the pattern difference of intrinsic hand muscles of upper limb‐onset ALS (UL‐ALS), upper limb‐onset progressive muscular atrophy (UL‐PMA), brachial amyotrophic diplegia (BAD), and Hirayama disease (HD) by measuring objective electrophysiological markers. Results: The abductor digiti minimi (ADM)/abductor pollicis brevis (APB) compound muscle action potential (CMAP) amplitude ratio was significantly higher in UL‐ALS than other variants, but a considerable proportion of UL‐ALS cases had an amplitude ratio in the range of other variants. Absent APB CMAP and abnormally high ADM/APB CMAP amplitude ratio (≥4) occurred only with UL‐ALS. Conversely, an absent ADM CMAP was identified only in UL‐PMA and BAD. Conclusions: The absolute ADM/APB CMAP amplitude ratio was not specific for ALS; however, several findings from simple electrophysiological measurements may help predict prognosis in patients with motor neuron diseases and may be early diagnostic markers for ALS. Muscle Nerve 51: 333–337, 2015     

Muscular fatigue and decremental response to repetitive nerve stimulation in X-linked spinobulbar muscular atrophy

Background and Purpose:  We report decremental responses to repetitive nerve stimulation (RNS) in 11 patients diagnosed with X-linked spinobulbar muscular atrophy (X-SBMA).
Methods:  The compound muscle action potential (CMAP) of the right abductor digiti minimi (ADM) and trapezius (TZ) in response to a 3-Hz stimulation of the ulnar nerve at the wrist and accessory nerve at the neck were recorded by surface electrodes.
Results:  A decremental response to RNS was observed in 90.9% of the TZ muscle and 27.2% in the ADM muscle of patients with X-SBMA.
Conclusion:  These electrophysiological features of X-SBMA are considered to be useful for diagnosis of X-SBMA. Furthermore, the waning phenomena that mostly appeared in the TZ muscle and increment of CMAP in RNS after the exercise also suggest a unique manifestation in X-SBMA.     

Can we accurately measure the onset latency to the first dorsal interosseous?

We present two cases with and without a latency difference of the compound muscle action potential (CMAP) from the abductor digiti minimi (ADM) and the first dorsal interosseous (FDI). In each case, onset latencies of FDI CMAPs using the contralateral small finger as E2 were shorter than those of belly-tendon CMAPs from the ADM and FDI. We conclude that onset of the belly-tendon FDI CMAP does not necessarily indicate initial activation of the FDI.     

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.     

单肢肌萎缩/平山病:41例患者临床、电生理和颈椎MRI特征分析

目的 探讨单肢肌萎缩(MMA)/平山病患者的临床、肌电图及颈椎MRI特征。方法 2009年5月至2014年5月就诊本科,符合诊断标准的患者,连续登记并详细记录及分析人口学资料、临床、电生理和颈椎自然位和屈曲位MRI资料。结果(1)共41例,男39例、女2例,发病年龄14～24岁、平均年龄(16.87±2.62)岁。病程1～121月、平均病程(22.13±26.25)月。双上肢均有临床症状者6例(14.6%),症状局限单侧者35例(85.4%); 单侧者左12例(29.3%)、右23例(56.1%)。冷麻痹22例,指震颤9例,手麻木4例; 41例均有手固有肌萎缩,均无感觉障碍;(2)症状侧尺和正中神经运动潜伏期延长,小指展肌、拇短展肌运动波幅减低,小指展肌/拇短展肌波幅比值减小;(3)症状侧针肌电图显示异常自发活动者的出现率,在第一骨间肌和小指展肌为100%、拇短伸肌90.1%、拇短展肌86.3%、肱桡肌16.8%、肱二头肌13.8%; 在仅限于单侧症状的35例患者中,无症状侧手固有肌也显示异常自发活动者占51.4%;(4)32例患者完成颈椎MRI检查。自然位时32例均显示颈2-颈7椎体后方下缘连线与椎体相交; 均显示下段颈髓萎缩变扁平,其中位于C5-C7节段14例,C5-C6节段6例,C6-C7节段7例,C5-T1节段5例; 屈颈位时15例显示硬膜腔后壁前移,移位的硬膜后方可见硬膜外占位,内有流空信号,恢复自然位后占位消失。9例显示髓内可疑T₂异常高信号。结论 MMA/平山病主要见于青少年男性; 电生理表现为低位颈髓前角细胞病变,且无症状侧可显示临床下神经源性损害; 小指展肌/拇短展肌波幅比值减小,是有鉴别意义的电生理指标; 屈颈位颈椎MRI对于诊断很重要。结合临床、神经电生理及影像表现,有助于更全面认识本病。     

Respiratory electrophysiological studies in Guillain-Barré syndrome.

Respiratory failure is a common and potentially life threatening complication in patients with Guillain-Barré syndrome. The incidence of phrenic nerve involvement and the predictive value of phrenic nerve conduction and diaphragmatic needle EMG were studied in 40 patients with Guillain-Barré syndrome within the first three days of admission to hospital. The negative peak onset latency of the diaphragmatic compound muscle action potential (CMAP), and its amplitude, duration, and area were abnormal in 83%. The need for ventilation was correlated with diaphragmatic CMAP amplitude (P = 0.005), and area (P = 0.001), but not with latency or duration. Abnormalities in diaphragmatic needle EMG were found in 45%, mainly a decreased number of motor unit potentials. The abnormalities correlated with the need for ventilation (P = 0.013). Of the 40% who required ventilation, all had either abnormal phrenic conduction, abnormal diaphragmatic needle EMG, or both. Eighty one per cent of the ventilated patients had abnormal forced vital capacity on the day of the electrophysiological examination. The results indicate that phrenic nerve conduction studies and diaphragmatic EMG are useful in detecting respiratory involvement in patients with Guillain-Barré syndrome and in identifying those at risk of respiratory failure.