Cortical versus spinal dysfunction in amyotrophic lateral sclerosis

Attarian, Shahram; Vedel, Jean‐Pierre; Pouget, Jean; Schmied, Annie

doi:10.1002/mus.20519

Cited by 23 publications

(28 citation statements)

References 65 publications

(107 reference statements)

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“…The other explanation, which we discussed in another recent study, may be the occurrence of spinal synaptic reorganization subsequent to motoneuron loss, leading to greater convergence of still intact corticomotoneuronal axons onto resilient motoneurons. 4 The second most frequently abnormal TMS parameter was the SP. Interestingly, in the patients with suspected or possible ALS, this was the most frequently abnormal parameter (Table 2), in agreement with our previous results.…”

Section: Discussionmentioning

confidence: 99%

Magnetic stimulation including the triple‐stimulation technique in amyotrophic lateral sclerosis

2007

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To study the relative importance of upper motor neuron (UMN) dysfunction in the weakness of amyotrophic lateral sclerosis (ALS) and to compare the sensitivity of several transcranial magnetic stimulation (TMS) parameters as means of assessing UMN impairment in ALS, we used TMS to evaluate one upper limb of 63 patients. The triple-stimulation technique (TST) and silent period (SP) were found to be the most frequently abnormal parameters (55.6% and 47.6%, respectively), without significant difference in their diagnostic sensitivity. The SP was found to be a useful parameter in patients with suspected or possible ALS. A positive correlation was found between weakness and the TST amplitude ratio, indicating that weakness may partly be caused by UMN dysfunction. Thus, the TST provides a quantitative tool for assessing UMN conduction failure. When used in association with the SP, the TST provides a sensitive diagnostic tool for use on ALS patients.

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Section: Discussionmentioning

confidence: 99%

Magnetic stimulation including the triple‐stimulation technique in amyotrophic lateral sclerosis

2007

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“…This may account for both the increase in excitatory and inhibitory responses, which decreased with time and disease progression. 3,4 The marked TMS-induced inhibitory effects on motor unit firing observed in this study may reflect a transient withdrawal of the motoneuron net excitatory drive induced by TMS (i.e., disfacilitation), as previously suggested. 6,11 This effect might involve cortical inhibitory processes recurrently activated by pyramidal collaterals, which are liable to effectively shut down the cortical contribution to the motoneuron excitatory drive.…”

Section: Discussionmentioning

confidence: 71%

“…In this study we showed that, in the early stages of ALS, inhibitory responses were increased, as is also the case for excitatory responses. 3 We propose that spinal reinnervation may occur in the earliest stage in patients in whom intact corticospinal axons lose some of their motoneuronal targets and branch to converge on surviving motoneurons. This may account for both the increase in excitatory and inhibitory responses, which decreased with time and disease progression.…”

Section: Discussionmentioning

confidence: 99%

“…Contrary to the TMS paired-pulse data obtained by recording surface electromyographic (EMG) activity in patients at rest, TMS-induced inhibitory responses have been reported to occur in single motor units (MUs) more often in ALS patients than in control subjects. 3,5,27 It should be noted, however, that most single motor unit studies in ALS patients have focused on the excitatory responses detected in peristimulus time histograms (PSTHs), which require application of suprathreshold TMS intensities. Under these conditions, purely inhibitory responses were only occasionally, if ever, recorded in either healthy subjects or patients.…”

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Changes in cortically induced inhibition in amyotrophic lateral sclerosis with time

2009

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Changes in intracortical inhibition have been detected by means of paired-pulse transcranial magnetic stimulation (TMS) based on electromyographic recordings in many neurological or psychiatric disorders, including amyotrophic lateral sclerosis (ALS). By contrast, inhibitory responses have been generally overlooked in single motor unit (MU) studies in patients with ALS. The aim of this study was to investigate the TMS-induced inhibitory responses of single MUs in peristimulus time histograms and the changes observed with time. For this purpose, 263 MUs were tested in 10 ALS patients in two to four recording sessions. Upon subdividing the data into epochs corresponding to mean disease durations of 12, 20, 32, 43, and 168 months, we found that inhibitory responses occurred more frequently than normal throughout the course of the disease and were stronger than normal during the first year after disease onset. This finding argues against the hypothesis that loss of inhibition may be part of the pathogenic process in ALS.

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“…However, some of the few single motor unit studies performed in patients with ALS have not been covered in this review. The interested reader may find additional information in Schmied et al (1999), Attarian et al (2006Attarian et al ( , 2008.…”

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Mechanisms underlying firing in healthy and sick human motoneurons

2015

Frontiers Research Topics

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Keywords: human motoneuron discharge mechanisms, motor unit, afterhyperpolarization and delayed depolarization, double and triple discharges, recruitment and rate coding, axon and peripheral afferents, excitability, motoneuron pathologyIn an address to the British Association for the Advancement of Science in Cambridge, Professor Sherrington introduced the terms "motor neurone" and "the final common path," the latter term implying that all motor commands converge onto the motoneuron which integrates the incoming information and passes the net information to the muscle for contraction (Sherrington, 1904). The relative ease of access of the spinal motoneuron made it feasible to set up techniques for investigating the physiological, biophysical and molecular properties of these neurons. It became the most investigated neuron of the CNS in the twentieth century and the information gained from studies on motoneurons formed the basis for examining the other neurons of the CNS. Since the compound action potential of a muscle unit is strictly related one-to-one to the action potential arriving from the innervating motoneuron, the statistical analysis of muscle unit action potentials provides an investigator with an elegant way to probe the properties of motoneurons in behaving humans. In the following review the terms motoneuron and motor unit might be used interchangeably. Different aspects of human motoneuron investigations in health and disease are presented in 16 articles of this topic which are summarized below.An increase in the net excitatory synaptic input to the motoneuron pool results in an increase in the level of muscle contraction by recruitment of additional motor units (MUs) and an increase in firing rates of the already recruited units (Milner-Brown et al., 1973;Henneman et al., 1974). The principle of orderly recruitment of motoneurons by size was originally proposed by Henneman (1957) but was later questioned by other researchers presenting examples of selective, rather than orderly recruitment (e.g., Smith et al., 1980). These controversies are assessed by Bawa et al. (2014), and the opinion unifying the concept of orderly recruitment is presented. In humans, increases in firing rates of motor units have been shown to follow the "onion skin" pattern at lower levels of contraction, meaning that the lower-threshold motor units discharge with higher rates than higher-threshold ones. However, studies performed on the whole range of muscle forces indicated that for higher force levels the motor unit firing rate follows a "reverse onion skin" pattern. Hu et al. (2014) decided to approach this problem using small surface electrodes and step increases in force instead of the "ramp and hold" protocols used by previous authors. They showed that the "onion skin" pattern was preserved until 15% of maximal voluntary contraction, and from their results predict this pattern to be valid for the whole range of muscle forces, which is not supported by the previous published works. However, the reported rate saturation ...

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Cortical versus spinal dysfunction in amyotrophic lateral sclerosis

Cited by 23 publications

References 65 publications

Magnetic stimulation including the triple‐stimulation technique in amyotrophic lateral sclerosis

Magnetic stimulation including the triple‐stimulation technique in amyotrophic lateral sclerosis

Changes in cortically induced inhibition in amyotrophic lateral sclerosis with time

Mechanisms underlying firing in healthy and sick human motoneurons

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