Posts Tagged motor-evoked potential
[Abstract] Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials
Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates.
Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA).
Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively.
Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand.
Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.
via Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials – Heidi M. Schambra, Jing Xu, Meret Branscheidt, Martin Lindquist, Jasim Uddin, Levke Steiner, Benjamin Hertler, Nathan Kim, Jessica Berard, Michelle D. Harran, Juan C. Cortes, Tomoko Kitago, Andreas Luft, John W. Krakauer, Pablo A. Celnik, 2019
[ARTICLE] Effects of 8-week sensory electrical stimulation combined with motor training on EEG-EMG coherence and motor function in individuals with stroke – Full Text
The peripheral sensory system is critical to regulating motor plasticity and motor recovery. Peripheral electrical stimulation (ES) can generate constant and adequate sensory input to influence the excitability of the motor cortex. The aim of this proof of concept study was to assess whether ES prior to each hand function training session for eight weeks can better improve neuromuscular control and hand function in chronic stroke individuals and change electroencephalography-electromyography (EEG-EMG) coherence, as compared to the control (sham ES). We recruited twelve subjects and randomly assigned them into ES and control groups. Both groups received 20-minute hand function training twice a week, and the ES group received 40-minute ES on the median nerve of the affected side before each training session. The control group received sham ES. EEG, EMG and Fugl-Meyer Assessment (FMA) were collected at four different time points. The corticomuscular coherence (CMC) in the ES group at fourth weeks was significantly higher (p = 0.004) as compared to the control group. The notable increment of FMA at eight weeks and follow-up was found only in the ES group. The eight-week rehabilitation program that implemented peripheral ES sessions prior to function training has a potential to improve neuromuscular control and hand function in chronic stroke individuals.
Stroke is one of the leading contributing factors to the loss of functional abilities and independence in daily life in adults1. The most common and widely observed impairment following stroke is motor impairment, which can be regarded as a loss or limitation of function in muscle control or movement2–5. Most stroke survivors later regain the ability to walk independently, but only fewer than 50% of them will have fully recovered upper extremity functions6,7. From a review focusing on motor recovery after stroke, it has been indicated that the recovery of both arm and hand function among subacute and chronic stroke survivors is limited in current neural rehabilitation settings4; therefore, additional management with activating plasticity before or during performing motor training is necessary for better motor recovery.
The fundamental principle of stroke rehabilitation is inducing brain plasticity by sensory or proprioceptive input in order to facilitate motor functions8,9. It has been demonstrated that strong sensory input can induce plastic changes in the motor cortex via direct or indirect pathways10–17. In this case, electrical stimulation (ES) that provides steady and adequate somatosensory input can be an ideal method of stimulating the motor cortex.
Recent studies using functional magnetic resonance imaging (fMRI) or transcranial magnetic stimulation (TMS) suggest that ES on peripheral nerves can increase motor-evoked potential (MEP)18–20, increase the active voxel count in the corresponding motor cortex13, and increase blood-oxygen-level dependent (BOLD) signals in fMRI, suggesting peripheral ES induced higher excitability and activation level of cortical neurons21. Since the expansion of the motor cortical area or increase in the excitability of neural circuits is associated with learning new motor skills22–26, clinicians should take advantage and assist patients with stroke on motor tasks training during this period of time. Celnik and colleagues27found that the hand function of chronic stroke subjects improved immediately after two-hour peripheral nerve stimulation combined with functional training, and the effect lasted for one day. Based on previous studies, the ES that increases corticomuscular excitability may turn out to be an ideal intervention added prior to traditional motor training to “activate” the neural circuit, so that patients may get the most out of the training. According to a recent study that applied single session peripheral ES on post-stroke individuals, the corticomuscular coherence (CMC), which is the synchronization level between EEG and EMG, increased significantly and was accompanied by improvement in the steadiness of force output28.
To our knowledge, however, there is no study investigating the long-term effect of ES combined with functional training on both motor performance and cortical excitability. We targeted the median nerve because its distribution covered the dorsal side of index, middle, and half of ring finger and the palmar side of the first three fingers and half of the ring finger. Besides, median nerve is in charge of the flexion of the first three fingers, which combined they accounts for most of the functional tasks of hand. Therefore, the purpose of this pilot study was to preliminarily evaluate the effect of eight-week ES-combined hand functional training among chronic stroke patients based on CMC and motor performance. We followed up for four weeks after the intervention ceased and examined the lasting effect. We hypothesized that those who received intervention with ES would have better hand function and higher CMC than those who received intervention with sham ES. We also hypothesized that the effect would last for at least four weeks during our follow-up.[…]
BACKGROUND: Modified constraint induced movement therapy (m-CIMT) discourages the use of the unaffected extremity and encourages the active use of the hemiplegic arm in order to restore the motor function. AIM: The aim was to assess the efficacy of m-CIMT on functional recovery of upper extremity (UE) in acute stroke patients, as compared to conventional rehabilitation therapy.
DESIGN: This is a prospective comparative study.
SETTING: This study included sixty patients with acute stroke recruited from neurology department.
METHODS: This study included sixty acute stroke patients. Inclusion criteria were: patients within two weeks from the onset of stroke, persistent hemiparesis leading to impaired upper extremity function, evidence of preserved cognitive function, and a minimum of 10 degrees of active finger extension and 20 degrees of active wrist extension. Exclusion criteria were: intra-cerebral hemorrhage, previous stroke on the same side, presence of neglect or a degree of aphasia impeding understanding of instructions, and conditions that limit the use of the upper limb before the stroke. Patients were assessed by Fugl-Meyer motor assessment (FMA), action research arm test (ARAT) and motor evoked potentials (MEPs), recorded from the abductor pollicis brevis (APB) of the affected hand. The clinical and neurophysiological tests were performed pre and postrehabilitation. The patients were divided into two groups: conventional rehabilitation program group (CRP) included 30 patients who were given a conventional rehabilitation program for two weeks. CIMT group included 30 patients who were subjected to modified CIMT for two consecutive weeks. Total treatment time was the same in both groups.
RESULTS: CRP group showed a non-significant improvement in FMA and ARAT. CIMT group showed a significant improvement in clinical scores on all tests (p < 0.05). When comparing both groups using FMA and ARAT tests pre- and post- therapy, a significant difference (p < 0.05) was found between both groups with CIMT group showing greater improvement. When comparing MEPs in CRP group, pre and postrehabilitation, a non-significant improvement was found for resting motor threshold (RMT), central motor conduction time (CMCT) and amplitude of MEPs. In contrast, each of the MEP parameters exhibited a significant improvement in CIMT group (p < 0.05).
CONCLUSION: In contrast to conventional rehabilitation therapy, modified CIMT revealed a significant functional and MEP improvement in acute stroke patients indicating that m-CIMT might be a more efficient treatment strategy.
CLINICAL REHABILITATION IMPACT: It is advised to use modified constraint movement therapy in rehabilitation of cerebrovascular stroke during acute stage.
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[ARTICLE] Direct and crossed effects of somatosensory electrical stimulation on motor learning and neuronal plasticity in humans – Full Text PDF
Purpose: Sensory input can modify voluntary motor function. We examined whether somatosensory electrical stimulation (SES) added to motor practice (MP) could augment motor learning, interlimb transfer, and whether physiological changes in neuronal excitability underlie these changes.
Methods: Participants (18–30 years, n = 31) received MP, SES, MP + SES, or a control intervention. Visuomotor practice included 300 trials for 25 min with the rightdominant wrist and SES consisted of weak electrical stimulation of the radial and median nerves above the elbow. Single- and double-pulse transcranial magnetic stimulation (TMS) metrics were measured in the intervention and nonintervention extensor carpi radialis.
Results: There was 27 % motor learning and 9 % (both p < 0.001) interlimb transfer in all groups but SES added to MP did not augment learning and transfer. Corticospinal excitability increased after MP and SES when measured at rest but it increased after MP and decreased after SES when measured during contraction. No changes occurred in intracortical inhibition and facilitation. MP did not affect the TMS metrics in the transfer hand. In contrast, corticospinal excitability strongly increased after SES with MP + SES showing sharply opposite of these effects.
Conclusion: Motor practice and SES each can produce motor learning and interlimb transfer and are likely to be mediated by different mechanisms. The results provide insight into the physiological mechanisms underlying the effects of MP and SES on motor learning and cortical plasticity and show that these mechanisms are likely to be different for the trained and stimulated motor cortex and the non-trained and non-stimulated motor cortex.
[ARTICLE] An investigation of cortical neuroplasticity following stroke in adults: is there evidence for a critical window for rehabilitation? – Full Text HTML
Evidence in animal stroke models suggests that neuroplasticity takes place maximally in a specific time window after an ischaemic lesion, which may coincide with the optimal time to intervene with rehabilitation. The aim of this study is to investigate neurophysiological evidence for a “critical window” of enhanced neuroplasticity in patients following ischaemic stroke, and establish its duration. We will also investigate changes in cortical inhibition following stroke, and the influence this has on functional recovery.
We will recruit participants recently admitted to the Stroke Unit of major metropolitan hospitals who have had a stroke and can provide informed consent. Participants will be excluded if they have any contraindications to Transcranial Magnetic Stimulation. We will compare neurophysiological outcomes in an age-matched healthy control group. We conservatively hypothesise a 5 % increase in neuroplasticity at the optimal timing following stroke, compared to control participants, and require 43 patients following stroke to detect a significant difference with 80 % power. The primary outcome is the change in the motor evoked potential (MEP) amplitude in a hand muscle, after the administration of a plasticity-inducing paradigm to the affected hemisphere. Secondary outcomes include measures of cortical excitability, intracortical inhibition and arm function.
The data from this trial will clarify whether there is a critical window for neuroplastic change in the brain following stroke. If so, intensive rehabilitation during this period could be more effective, reducing long-term disability and the cost burden of stroke.
[WEB SITE] Factors Associated With Upper Extremity Motor Recovery After Repetitive Transcranial Magnetic Stimulation in Stroke Patients – Full Text HTML
To determine factors associated with motor recovery of the upper extremity after repetitive transcranial magnetic stimulation (rTMS) treatment in stroke patients.
Twenty-nine patients with subacute stroke participated in this study. rTMS was applied to the hand motor cortex for 10 minutes at a 110% resting motor threshold and 10 Hz frequency for two weeks. We evaluated the biographical, neurological, clinical, and functional variables, in addition to the motor-evoked potential (MEP) response. The Manual Function Test (MFT) was performed before, immediately after, and two weeks after, the treatment. Patients were divided into a responder and non-responder group according to their respective improvements on the MFT. Data were compared between the two groups.
Patients with exclusively subcortical stroke, absence of aphasia, the presence of a MEP response, high scores on the Mini-Mental Status Examination, Motricity Index arm score, Functional Independence Measure, and Functional Ambulatory Classification; and a shorter period from stroke onset to rTMS were found to be significantly associated with a response to rTMS.
The results of this study suggest that rTMS may have a greater effect on upper extremity motor recovery in stroke patients who have a MEP response, suffer an exclusively subcortical stroke, mild paresis, and have good functional status. Applying rTMS early would have additional positive effects in the patients with the identified characteristics.