Reliability of intracortical and corticomotor excitability estimates obtained from the upper extremities in chronic stroke

Division of Geriatrics, Faculty of Medicine, Department of Neurology and Neurosurgery, McGill University, Canada.
Neuroscience Research (Impact Factor: 1.94). 06/2007; 58(1):19-31. DOI: 10.1016/j.neures.2007.01.007
Source: PubMed


We estimated the trial-to-trial variability and the test-retest reliability of several intracortical and corticomotor excitability parameters for the upper extremity in chronic stroke patients. Nine patients with hemiparesis of the upper extremity were enrolled 8-17 months after a unilateral stroke. Transcranial magnetic stimulation was used to obtain repeated measures over a two week interval of motor evoked potential (MEP) recruitment curves and cortical silent periods in the first dorsal interosseus muscle of each hand. Five trials would have provided accurate estimates of the MEP amplitude and silent period duration for the unlesioned side in all patients, but 25% of the datasets from the lesioned side provided poor estimates of MEP amplitude even with 10 trials. Intraclass correlations were >0.70 for all parameters obtained from the lesioned side and for the MEP amplitude, slope of the recruitment curve, silent period, and silent period slope from the unlesioned side. MEP amplitude varied across sessions within subject by 20% on both sides, whereas other parameters showed less variability on the unlesioned side relative to the lesioned side. The Fugl-Meyer upper extremity motor score and the time to complete the 6 fine-motor items from the Wolf Motor Function Test (WMFT) were also found to be highly reliable over this interval. We conclude that the functional and most of the excitability parameters are reliable across time in patients with variable lesions due to stroke. Due to high intrasubject variability, the use of some excitability parameters as indicators of functional neuroplasticity in response to treatment may be limited to interventions with large effect sizes.

Download full-text


Available from: Carolee Winstein, Jul 03, 2014
35 Reads
  • Source
    • "In conditions that lead to a prolonged MEP, this could mask concurrent shortening of the SP duration. In patients with stroke, increased MEP latencies have been found in the sub-acute phase post stroke, shifting towards more normal values with progressive stages of recovery [27,28]. If the stimulus onset is used to define the SP onset, changes in MEP latency might affect the SP duration in stroke patients. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To explore if stimulus-response (S-R) characteristics of the silent period (SP) after transcranial magnetic stimulation (TMS) are affected by changing the SP definition and by changing data presentation in healthy individuals. This information would be clinically relevant to predict motor recovery in patients with stroke using stimulus-response curves. Different landmarks to define the SP onset and offset were used to construct S-R curves from the biceps brachii (BB) and abductor digiti minimi (ADM) muscles in 15 healthy participants using rectified versus non-rectified surface electromyography (EMG). A non-linear mixed model fit to a sigmoid Boltzmann function described the S-R characteristics. Differences between S-R characteristics were compared using paired sample t-tests. The Bonferroni correction was used to adjust for multiple testing. For the BB, no differences in S-R characteristics were observed between different SP onset and offset markers, while there was no influence of data presentation either. For the ADM, no differences were observed between different SP onset markers, whereas both the SP offset marker "the first return of any EMG-activity" and presenting non-rectified data showed lower active motor thresholds and less steep slopes. The use of different landmarks to define the SP offset as well as data presentation affect SP S-R characteristics of the ADM in healthy individuals.
    Journal of NeuroEngineering and Rehabilitation 01/2014; 11(1):1. DOI:10.1186/1743-0003-11-1 · 2.74 Impact Factor
  • Source
    • "80% RMT), with the assumption that this intensity would elicit a similar magnitude of inhibition/facilitation in each individual. However, these approaches show a high degree of between-subject (Boroojerdi et al., 2000; Wassermann 2002; Orth et al., 2003) and across session (Maeda et al., 2002) variability in both healthy and stroke populations (Orth et al., 2003; Koski et al., 2007). Recent work has demonstrated that paired pulse TMS protocols that identify thresholds for the onset of inhibition and facilitation, rather than measure the magnitude of these effects, show reduced variability for the measurement of these effects (Orth et al., 2003) and can detect hemispheric differences in both inhibitory and facilitatory activity in clinical populations (Stinear and Byblow 2004; Edwards et al., 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: The purpose of the present study was to assess changes in thresholds for the onset of short intracortical inhibition (SICI) and intracortical facilitation (ICF) in individuals with chronic stroke compared to age-matched healthy adults and evaluate the relationship between these thresholds and motor function in the chronic stroke group. Methods: Paired-pulse transcranial magnetic stimulation was used to derive thresholds for the onset of SICI and ICF in 12 neurologically healthy and 12 individuals with chronic stroke. Motor evoked potentials were elicited by a test stimulus of fixed intensity preceded by a conditioning stimulus ranging from 0%-125% of active motor threshold to generate recruitment curves. Regression functions were fit to these recruitment curves to identify thresholds for the onset of SICI and ICF. Mixed measures analysis of variance was used to compare thresholds for each hemisphere within and between groups. Results: Results showed a significant three-way interaction between Group (stroke, healthy), Hemisphere (ipsilesional, contralesional) and Stimulus interval (2 ms, 12 ms). Significant differences in the thresholds for the onset of both SICI and ICF were present in individuals with chronic stroke, with no between hemisphere differences for the control group. When compared to age-matched controls, comparisons revealed significant reductions in ipsilesional, but not contralesional thresholds for the onset of ICF, and significant reductions in contralesional, but not ipsilesional, thresholds for the onset of SICI in individuals with chronic stroke. In addition, as thresholds for ICF and SICI in stroke patients approached the level of healthy adults, higher function on the Wolf Motor Function Test was observed. Conclusions: Reduced thresholds for the onset of SICI and ICF observed in the present study indicate that both inhibitory and facilitatory systems mediate changes in cortical excitability in chronic stroke patients. The association between higher onset thresholds and motor function in the stroke group also suggests that these thresholds have potential utility for tracking functional motor improvements in patients with chronic stroke. This study provides new insights to further characterize changes in intracortical neurotransmission that play an important role in modulating neuroplasticity and the potential relationship between inhibitory and facilitatory networks and motor function post-stroke.
    08/2013; 31(6). DOI:10.3233/RNN-120300
  • Source
    • "The required effort of manual analysis becomes worse when computing cSP stimulus–response curves to assess cortical inhibition (Kimiskidis et al., 2005; Werhahn et al., 2007). These input–output characteristics of cSP, much like with MEPs, provide tools for the assessment of motor cortex function, and have potential in assessing pharmacological manipulation, and quantifying neuronal dysfunction and disease progression in various neurological disorders (Kazis et al., 2006; Kimiskidis et al., 2006; Koski et al., 2007). Few automated routines have been developed to allow for quick and effortless analysis of cSPs (Daskalakis et al., 2003; Garvey et al., 2001; King et al., 2006; Nilsson et al., 1997; Rabago et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cortical silent period (cSP) is a short interruption in electromyography (EMG) during active muscle contraction induced with transcranial magnetic stimulation (TMS). The cSP is a measure of cortical inhibition and is believed to represent inhibitory interneuron effects on excited motor cortical areas. Several pathological conditions and pharmacological manipulations induce changes to cSP duration indicating alterations in intracortical inhibition. At present, it is common to manually analyse the cSP duration from measured EMG. However, to avoid inter-examiner effects on cSP interpretation and detection, as well as to allow for quick measurement online, automated routine would be preferable. In this study, we evaluate the feasibility of a straight-forward cSP detection routine based on analysing the rectified first derivative of the EMG signal following TMS. Previously measured cSPs of 54 healthy subjects were reanalysed manually by two of the authors and using the automated routine. Furthermore, we recruited one subject for whom the cSPs were induced with several stimulation intensities, and those cSPs were analysed manually by two of the authors as well as using the automated routine. We found that cSPs were detected correctly by the automated cSP detection routine, and agreement with manually analysed subject-specific mean cSPs was excellent (ICC=0.992, p<0.001). The inter-examiner variability was similar to the variability between manual and automated analysis. Hence, we believe the introduced cSP detection routine would be feasible for online cSP detection, in such a way that is presently used to detect the motor evoked potentials.
    Journal of Neuroscience Methods 05/2013; 217(1). DOI:10.1016/j.jneumeth.2013.04.019 · 2.05 Impact Factor
Show more