Advancing disease monitoring of amyotrophic lateral sclerosis with the compound muscle action potential scan

ObjectiveTo determine which compound muscle action potential (CMAP) scan-derived electrophysiological markers are most sensitive for monitoring disease progression in amyotrophic lateral sclerosis (ALS), and whether they hold value for clinical trials.MethodsWe used four independent patient cohorts to assess longitudinal patterns of a comprehensive set of electrophysiological markers including their association with the ALS functional rating scale (ALSFRS-R). Results were translated to trial sample size requirements.ResultsIn 65 patients, 225 thenar CMAP scan recordings were obtained. Electrophysiological markers showed extensive variation in their longitudinal trajectories. Expressed as standard deviations per month, motor unit number estimation (MUNE) values declined by 0.09 (CI 0.07–0.12), D50, a measure that quantifies CMAP scan discontinuities, declined by 0.09 (CI 0.06–0.13) and maximum CMAP by 0.05 (CI 0.03–0.08). ALSFRS-R declined fastest (0.12, CI 0.08 – 0.15), however the between-patient variability was larger compared to electrophysiological markers, resulting in larger sample sizes. MUNE reduced the sample size by 19.1% (n = 388 vs n = 314) for a 6-month study compared to the ALSFRS-R.ConclusionsCMAP scan-derived markers show promise in monitoring disease progression in ALS patients, where MUNE may be its most suitable derivate.SignificanceMUNE may increase clinical trial efficiency compared to clinical endpoints.     

Pulmonary function tests and diaphragmatic compound muscle action potential in patients with sporadic amyotrophic lateral sclerosis

Sathyaprabha TN, Pradhan C, Nalini A, Thennarasu K, Raju TR. Pulmonary function tests and diaphragmatic compound muscle action potential in patients with sporadic amyotrophic lateral sclerosis.
Acta Neurol Scand: 2010: 121: 400–405.
© 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Background – Respiratory failure is the primary cause of death in patients with amyotrophic lateral sclerosis (ALS). Diaphragmatic compound muscle action potentials (DCMAP) are valid parameters to assess the respiratory muscle innervation. Aim – In this study we propose to establish evidence of pulmonary dysfunction in patients with ALS and its relation to DCMAP parameters among patients with sporadic ALS. Materials and methods – Twenty nine patients (M‐20, F‐9) diagnosed to have sporadic ALS by El. Escorial criteria, without symptoms of pulmonary dysfunction, and able to perform the PFT satisfactorily, were studied. Thirty controls (M‐20, F‐10) were selected from patient’s relatives. Forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), peak expiratory flow rate (PEFR) and maximum voluntary ventilation (MVV) were measured by spirometry. Maximum expiratory pressure (MEP) was measured by digital peak pressure monitor. Right phrenic nerve conductions (DCMAP) were performed and the latencies and amplitude of diaphragmatic com‐pound action potential (DCMAP) was recorded in controls and ALS patients. Results – The mean age of patients was 51.41 ± 10.72 years (37–82) and control was 53.57 ± 8.85 years (30–68). None of the patients had symptoms or clinical evidence of respiratory dysfunction. The FVC, FEV1, PEFR, MVV, MIP and MEP were significantly (P < 0.001) reduced in ALS. The mean DCMAP amplitude was reduced among patients (610 ± 506.231 μv) as compared to controls (1303.33 ± 584.56, P < 0.001) and mean latency was increased in patients (9.73 ± 2.57 ms) compared to controls (7.69 ± 0.87, P = 0.001). There was significant negative correlation between PFTs and latencies of DCMAP. Amplitude of DCMAP did not correlate with PFTs. Conclusion – There is significant negative correlation between DCMAP latencies and PFTs suggesting early loss of myelinated fibres and diaphragmatic dysfunction. DCMAP latencies may be a good indicator of early respiratory muscle involvement and also of disease progression in ALS.     

Diagnostic accuracy of nerve excitability and compound muscle action potential scan derived biomarkers in amyotrophic lateral sclerosis

Background and purpose

The lack of reliable early biomarkers still causes substantial diagnostic delays in amyotrophic lateral sclerosis (ALS). The aim was to assess the diagnostic accuracy of a novel electrophysiological protocol in patients with suspected motor neuron disease (MND).

Methods

Consecutive patients with suspected MND were prospectively recruited at our tertiary referral centre for MND in Utrecht, The Netherlands. Procedures were performed in accordance with the Standards for Reporting of Diagnostic Accuracy. In addition to the standard diagnostic workup, an electrophysiological protocol of compound muscle action potential (CMAP) scans and nerve excitability tests was performed on patients' thenar muscles. The combined diagnostic yield of nerve excitability and CMAP scan based motor unit number estimation was compared to the Awaji and Gold Coast criteria and their added value was determined.

Results

In all, 153 ALS or progressive muscular atrophy patients, 63 disease controls and 43 healthy controls were included. Our electrophysiological protocol had high diagnostic accuracy (area under the curve [AUC] 0.85, 95% confidence interval [95% CI] 0.80–0.90), even in muscles with undetectable axon loss (AUC 0.78, 95% CI 0.70–0.85) and in bulbar-onset patients (AUC 0.85, 95% CI 0.73–0.95). Twenty-four of 33 (73%) ALS patients who could not be diagnosed during the same visit were correctly identified, as well as 8/13 (62%) ALS patients not meeting the Gold Coast criteria and 49/59 (83%) ALS patients not meeting the Awaji criteria during this first visit.

Conclusions

Our practical and non-invasive electrophysiological protocol may improve early diagnosis in clinically challenging patients with suspected ALS. Routine incorporation may boost early diagnosis, enhance patient selection and generate baseline measures for clinical trials.     

肌萎缩侧索硬化患者复合肌肉动作电位特点分析及其与临床关系的研究

目的分析肌萎缩侧索硬化患者复合肌肉动作电位之特点,探讨波幅改变与肌力、病程以及神经功能等级评分等方面的关系。方法收集2001年5月-2004年11月肌电图检查表现为广泛神经源性损害的肌萎缩侧索硬化患者127例,根据ElEscorial诊断标准,确诊级43例、拟诊级39例、可能级13例、可疑级32例。选择其中确诊级和拟诊级患者82例进行神经功能评分和Appel肌萎缩侧索硬化量表评分,然后对其复合肌肉动作电位波幅值与肌力、病程以及神经功能评分变化间的关系进行比较分析。结果(1)82例患者复合肌肉动作电位波幅下降,与肌力改变呈明显指数拟合关系(r=0.969,P=0.001)。(2)同一患者波幅水平随病程而逐渐降低,波幅下降速度较慢者病程较长;不同患者的波幅与病程无显著相关(r=!0.077,P=0.502)。(3)复合肌肉动作电位波幅水平降低与神经功能等级评分呈显著正相关(r=0.412,P=0.001),与Appel评分呈显著负相关(r=!0.549,P=0.001)。(4)患者复合肌肉动作电位波幅水平的降低与运动神经传导速度无明显相关(r=!0.087,P=0.545),但若将波幅与传导速度转换为正常下限的百分比取其平方根后,二者间则呈线性相关(r=0.382,P<0.001)。结论复合肌肉动作电位波幅改变是肌萎缩侧索硬化原发性与继发性病理改变共同作用的结果,随着患者肌无力和肌萎缩症状的逐渐加重,复合肌肉动作电位波幅亦明显下降,但由于此时髓鞘仍保留完整,传导速度仍可保持正常,提示肌萎缩侧索硬化患者肌力下降的机制主要系下运动神经元损害所致。在同一患者,复查时显示复合肌肉动作电位波幅随病程进展而逐渐下降,但尚难建立反映二者平行关系的时间-波幅曲线,提示复合肌肉动作电位波幅改变与病程关系较为复杂。此外,复合肌肉动作电位波幅与肌萎缩侧索硬化患者的神经功能等级评分和Appel量表评分明显相关,提示早期波幅下降较慢者病情相对较轻。     

血清肌酸激酶与肌萎缩侧索硬化的相关性

目的 探讨血清肌酸激酶(CK)与肌萎缩侧索硬化(ALS)疾病进展率的相关性.方法 分析144例ALS患者和100例健康体检者的临床信息,分析不同亚组ALS患者血清CK差异及与疾病进展率(△FS表示)的相关性.结果 ALS患者血清CK水平男性与女性分别为224.6± 19.3U·L-1、137.8±15.1 U·L-1,对照组分别为63.5±5.3U·L-1、60.2±4.8U·L-1,P值分别＜0.001和0.023,表明无论男性还是女性ALS患者血清CK水平均较对照组升高,差异有统计学意义.另外从年龄来看,无论是＜60岁(209.1±19.6 U·L-1)还是＞60岁(161.3±18.3U·L-1)的ALS患者血清CK水平均较对照组明显升高(P值分别为0.001和0.005).然而ALS患者血清CK水平与ALSFRS-R评分及△FS不存在相关性.对发病部位进行调整后,仅肢体起病ALS患者血清CK与△FS存在弱相关(R2=0.18,P=0.006).结论 ALS患者血清CK水平升高,与疾病进展率不存在相关性.     

Mechanisms defining the action potential abnormalities in simulated amyotrophic lateral sclerosis

The present study investigates action potential abnormalities obtained in simulated cases of three progressively greater degrees of uniform axonal dysfunctions. The kinetics of the currents, defining the action potential propagation through the human motor nerve in the normal and abnormal cases, are also given and discussed. These computations use our previous multi-layered model of the myelinated motor axon, without taking into account the aqueous layers within the myelin sheath. The results show that the classical "transient" Na(+) current contributes mainly to the action potential generation in the nodal segments, as the contribution of the nodal fast and slow potassium currents to the total nodal ionic current is negligible. However, the ionic channels beneath the myelin sheath are insensitive to the short-lasting current stimuli and do not contribute to action potential generation in the internodal compartments along the fibre length. The slight changes obtained in the currents underlying the generated action potentials in the three amylotropic lateral sclerosis cases are consistent with the effect of uniform axonal dysfunction along the fibre length. Nevertheless that the uniform axonal dysfunction progressively increases in the nodal and internodal segments of each next simulated amylotropic lateral sclerosis case, the action potentials cannot be regarded as definitive indicators for the progressive degrees of this disease.     

The motor cortex and amyotrophic lateral sclerosis

On theoretical grounds, abnormalities of the motor cortex in patients with amyotrophic lateral sclerosis (ALS) could lead to anterograde ("dying-forward") transneuronal degeneration of the anterior horn cells as suggested by Charcot. Conversely, retrograde ("dying-back") degeneration of the corticospinal tracts could affect the motor cortex. Evidence derived from clinical, neuropathological, static, and functional imaging, and physiological studies, favors the occurrence of anterograde degeneration. It is hypothesized that transneuronal degeneration in ALS is an active excitotoxic process in which live but dysfunctional corticomotoneurons, originating in the primary motor cortex, drive the anterior horn cell into metabolic deficit. When this is marked, it will result in more rapid and widespread loss of lower motor neurons. In contrast, slow loss of corticomotoneurons, as occurs in primary lateral sclerosis (PLS), precludes excitotoxic drive and is incompatible with anterograde degeneration. Preservation of slow-conducting non-M1 direct pathways in PLS is not associated with excitotoxicity, and anterior horn cells survive for long periods of time.     

Functional motor compensation in amyotrophic lateral sclerosis

The present study investigated the fMRI correlates of functional compensation/neural reorganization of the motor system in patients with amyotrophic lateral sclerosis (ALS). The hypothesis was that ALS patients would recruit additional brain regions compared with controls in a motor task and that activity in these regions would vary as a function of task difficulty. Patients and controls executed a motor task with two sequences (a simple and a more difficult one) of consecutive button presses. Patients and controls both activated brain regions known to be involved in motor execution and control. Activity in ipsilateral motor areas as well as difficulty-related activity in the left cerebellum could only be observed in patients. The behavioral data indicated that the motor task was much more difficult for patients than for controls. At nearly equal difficulty the observed patterns of hemodynamic activity in controls were very similar to those observed in ALS. The findings suggest that functional compensation in ALS relies on existing resources and mechanisms that are not primarily developed as a consequence of the lesion.     

Quantitative motor assessment in amyotrophic lateral sclerosis

Reliable measurements are needed to document the natural history of ALS and to determine therapeutic efficacy. We have devised a standardized protocol that generates interval data sensitive to change-the Tufts Quantitative Neuromuscular Exam (TQNE). The TQNE consists of the following four major categories: pulmonary function, oropharyngeal function, timed functional activities, and isometric strength using an electronic strain gauge. The 29-item exam takes about 1 hour to administer and has excellent test-retest reliability.     

Changes in motor cortex excitability during muscle fatigue in amyotrophic lateral sclerosis

To further investigate the pathophysiology of amyotrophic lateral sclerosis (ALS), the silent period (SP) evoked by transcranial magnetic stimulation during a fatiguing muscle contraction was evaluated in 15 patients and in 15 healthy subjects. Physiological lengthening of the SP duration was not observed in patients with disease duration of > or = 2 years. Decreased intracortical inhibition, probably secondary to dysfunction of the inhibitory interneurons that modulate the corticomotoneuronal firing, appears in later stages of disease. Normal motor cortex adaptation is impaired and cortical hyperexcitability might be unmasked during fatigue in ALS patients with longer disease duration.     

Correlation between structural and functional connectivity impairment in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, characterized by progressive loss of motor function. While the pathogenesis of ALS remains largely unknown, imaging studies of the brain should lead to more insight into structural and functional disease effects on the brain network, which may provide valuable information on the underlying disease process. This study investigates the correlation between changes in structural connectivity (SC) and functional connectivity (FC) of the brain network in ALS. Structural reconstructions of the brain network, derived from diffusion weighted imaging (DWI), were obtained from 64 patients and 27 healthy controls. Functional interactions between brain regions were derived from resting‐state fMRI. Our results show that (i) the most structurally affected connections considerably overlap with the most functionally impaired connections, (ii) direct connections of the motor cortex are both structurally and functionally more affected than connections at greater topological distance from the motor cortex, and (iii) there is a strong positive correlation between changes in SC and FC averaged per brain region (r = 0.44, P < 0.0001). Our findings indicate that structural and functional network degeneration in ALS is coupled, suggesting the pathogenic process affects both SC and FC of the brain, with the most prominent effects in SC. Hum Brain Mapp 35:4386–4395, 2014. © 2014 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.     

肌萎缩侧索硬化患者肌电图与ALS-FRS-R的研究

目的研究肌萎缩侧索硬化(ALS)患者肌电图(EMG)相关肌肉小力收缩时运动单位动作电位(MUAP)的波幅(Amp)和时限(Lat)与肌萎缩侧索硬化功能评分(ALS-FRS-R)之间的相关性。方法 25例ALS患者分别进行ALS-FRS-R和EMG检查,分别记录并分析左右胫骨前肌、左右伸指总肌、腹直肌及胸锁乳突肌小力收缩时MUAP的Amp和Lat与ALS-FRS-R的相关性。结果 23例ALS患者右胫骨前肌小力收缩时Amp与ALS-FRS-R存在相关性,R2=0.173,P=0.043。左胫骨前肌、左右伸指总肌、腹直肌及胸锁乳突肌小力收缩时的Amp及左右胫骨前肌、左右伸指总肌、腹直肌及胸锁乳突肌小力收缩时的Lat与ALS-FRS-R不存在相关性(P>0.05)。结论 EMG中仅个别相关肌肉小力收缩时MUAP的Amp与ALS-FRS-R相关,因此EMG相关肌肉小力收缩时的Amp和Lat对ALS仅具有定性意义,不能反映ALS患者病情的严重程度。     

Correlation between clinical phenotype and electromyographic parameters in amyotrophic lateral sclerosis

Introduction

Even if electromyography (EMG) is routinely used to confirm the diagnosis of amyotrophic lateral sclerosis (ALS), few studies have analysed the correlation between electrophysiological parameters and clinical characteristics of ALS. We assessed if the quantification of active denervation (AD) and chronic denervation (CD) provides clinicians with information about phenotype, disease progression and survival in ALS patients.

Methods

We studied a cohort of 689 ALS patients recording the following parameters: age and site of onset, survival, MRC scale for muscle strength evaluation, burden of upper and lower motor signs as measured with specific scales (PUMNS and LMNS, respectively), ALSFRS-R, progression rate (ΔFS), MITOS and King’s Staging systems (KSS). We performed EMG on 11 muscles, and calculated semiquantitative AD and CD scores for each limb, as well as for the bulbar and spinal regions.

Results

We found a positive correlation between AD and CD scores with LMNS (respectively p = 4.4 × 10^–37 and p = 2.8 × 10^–45) and a negative correlation with MRC (respectively p = 4.5 × 10^–35 and p = 3.0 × 10^–35). Furthermore, patients with higher spinal AD and CD scores had significantly lower ALSFRS-R scores, and higher KSS and MITOS stages. Conversely, only AD was associated to higher ΔFS (p = 1.0 × 10^–6) and shorter survival (p = 1.1 × 10^–5).

Conclusion

Our results confirmed that EMG examination represents not only a diagnostic instrument, but also a prognostic tool. In this context, AD seems to be a reliable predictor of disease’s progression and survival while CD better describes functional disability.

     

Microglia as potential contributors to motor neuron injury in amyotrophic lateral sclerosis

The central nervous system (CNS) is equipped with a variety of cell types, all of which are assigned particular roles during the development, maintenance, function and repair of neural tissue. One glial cell type, microglia, deserves particular attention, as its role in the healthy or injured CNS is incompletely understood. Evidence exists for both regenerative and degenerative functions of these glial cells during neuronal injury. This review integrates the current knowledge of the role of microglia in an adult-onset neurodegenerative disease, amyotrophic lateral sclerosis (ALS), and pays particular attention to the possible mechanisms of initiation and propagation of neuronal damage during disease onset and progression. Microglial cell properties, behavior and detected inflammatory reactions during the course of the disease are described. The neuroinflammatory changes that occur in a mouse model of ALS are summarized. The understanding of microglial function in the healthy and injured CNS could offer better diagnostic as well as therapeutic approaches for prevention, retardation, or repair of neural tissue degeneration.     

Effect of ultrahigh-dose methylcobalamin on compound muscle action potentials in amyotrophic lateral sclerosis: A double-blind controlled study

To develop a symptomatic treatment for amyotrophic lateral sclerosis, we compared the effects of ultrahigh-dose and low-dose (25 and 0.5 mg/day, intramuscularly, for 14 days) methylcobalamin on averaged compound muscle action potential amplitudes (CMAPs) in a double-blind trial. No significant changes in CMAP amplitude were found in 12 patients who had the low-dose treatment at either 2 or 4 weeks after start of treatment. By contrast, 12 patients assigned to the ultrahigh-dose group demonstrated a significant increase at 4 weeks. This method may provide a clinically useful measure to improve or retard muscle wasting, if a larger extended trial fulfills its promise. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1775–1778, 1998     

Distal motor axonal dysfunction in amyotrophic lateral sclerosis

Nerve conduction slowing in amyotrophic lateral sclerosis (ALS) is usually caused by loss of fast motor axons. We studied the frequency, extent, and distribution of prominently prolonged distal motor latencies in ALS. We reviewed results of median, ulnar, and tibial nerve conduction studies in 91 patients with ALS, 24 with lower motor neuron disorders, and 36 with axonal neuropathy. Coincidental carpal tunnel syndrome was found for 4 (4.4%) of the ALS patients who were excluded from analyses. Markedly prolonged distal latencies (>125% of the upper limit of normal) were found only in the median nerve of ALS patients (9%), and in none of the disease controls. Excitability studies suggested membrane depolarization in some ALS patients. Our results show that approximately 10% of ALS patients shows prominently prolonged median distal latency, which cannot be explained by axonal loss and carpal tunnel lesion. The distal nerve conduction slowing may partly be caused by membrane depolarization possibly due to motor neuronal degeneration in ALS. We suggest that recognition of the pattern of distal motor axonal dysfunction predominant in the median nerve is clinically important, and could provide additional insights into the pathophysiology of ALS.