Hemispheric Differences of 1 Hz rTMS over Motor and Premotor Cortex in Modulation of Neural Processing and Hand Function.

INTRODUCTION: Non-invasive brain stimulation can modulate both neural processing and behavioral performance. Its effects may be influenced by the stimulated area and hemisphere. In this study (EC no. 09083), repetitive transcranial magnetic stimulation (rTMS) was applied to the primary motor cortex (M1) or dorsal premotor cortex (dPMC) of either the right or left hemisphere, while evaluating cortical neurophysiology and hand function. METHODS: Fifteen healthy subjects participated in this placebo-controlled crossover study. Four sessions of real 1 Hz rTMS (110% of rMT, 900 pulses) over (i) left M1, (ii) right M1, (iii) left dPMC, (iv) right dPMC, and one session of (v) placebo 1 Hz rTMS (0% of rMT, 900 pulses) over the left M1 were applied in randomized order. Motor function of both hands (Jebsen-Taylor Hand Function Test (JTHFT)) and neural processing within both hemispheres (motor evoked potentials (MEPs), cortical silent period (CSP), and ipsilateral silent period (ISP)) were evaluated prior and after each intervention session. RESULTS: A lengthening of CSP and ISP durations within the right hemisphere was induced by 1 Hz rTMS over both areas and hemispheres. No such intervention-induced neurophysiological changes were detected within the left hemisphere. Regarding JTHFT and MEP, no intervention-induced changes ensued. Changes of hand function correlated with neurophysiological changes within both hemispheres, more often for the left than the right hand. CONCLUSIONS: Effects of 1 Hz rTMS can be better captured by neurophysiological than behavioral measures. Hemispheric differences need to be considered for this intervention.

Resting motor threshold in the course of hand motor recovery after stroke: a systematic review.

BACKGROUND: Resting motor threshold is an objective measure of cortical excitability. Numerous studies indicate that the success of motor recovery after stroke is significantly determined by the direction and extent of cortical excitability changes. A better understanding of this topic (particularly with regard to the level of motor impairment and the contribution of either cortical hemisphere) may contribute to the development of effective therapeutical strategies in this cohort. OBJECTIVES: This systematic review collects and analyses the available evidence on resting motor threshold and hand motor recovery in stroke patients. METHODS: PubMed was searched from its inception through to 31/10/2020 on studies investigating resting motor threshold of the affected and/or the non-affected hemisphere and motor function of the affected hand in stroke cohorts. RESULTS: Overall, 92 appropriate studies (including 1978 stroke patients and 377 healthy controls) were identified. The analysis of the data indicates that severe hand impairment is associated with suppressed cortical excitability within both hemispheres and with great between-hemispheric imbalance of cortical excitability. Favorable motor recovery is associated with an increase of ipsilesional motor cortex excitability and reduction of between-hemispheric imbalance. The direction of change of contralesional motor cortex excitability depends on the amount of hand motor impairment. Severely disabled patients show an increase of contralesional motor cortex excitability during motor recovery. In contrast, recovery of moderate to mild hand motor impairment is associated with a decrease of contralesional motor cortex excitability. CONCLUSIONS: This data encourages a differential use of rehabilitation strategies to modulate cortical excitability. Facilitation of the ipsilesional hemisphere may support recovery in general, whereas facilitation and inhibition of the contralesional hemisphere may enhance recovery in severe and less severely impaired patients, respectively.

Noninvasive brain stimulation in rehabilitation of hemispatial neglect after stroke.

BACKGROUND: Noninvasive brain stimulation can modulate neural processing within the motor cortex and thereby might be beneficial in the rehabilitation of hemispatial neglect after stroke. METHODS: We review the pertinent literature regarding the use of transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation in order to facilitate recovery of hemispatial neglect after stroke. RESULTS: Twenty controlled trials (including 443 stroke patients) matched our inclusion criteria. Methodology and results of each study are presented in a comparative approach. Current data seem to indicate a better efficiency of repetitive transcranial magnetic stimulation, compared to tDCS to ameliorate hemispatial neglect after stroke. CONCLUSIONS: Noninvasive brain stimulation has the potential to facilitate recovery of hemispatial neglect after stroke, but until today, there are not enough data to claim its routine use.

Cycle ergometer training vs resistance training in ICU-acquired weakness.

OBJECTIVES: We investigated the effectiveness of cycle ergometer training and resistance training to enhance the efficiency of standard care to improve walking ability, muscular strength of the lower limbs, cardiovascular endurance and health-related quality of life during inpatient rehabilitation in intensive care unit acquired weakness. MATERIALS & METHODS: Thirty-nine patients with severe to moderate walking disability were enrolled in one of the three experimental groups: (a) ergometer training group, (b) resistance training group and (c) control group (standard care only). Intervention was applied 5 days a week over a 4-week period during inpatient neurological rehabilitation. We evaluated walking ability (Functional Ambulation Category test, timed up and go test, 10-metre walk test and 6-minute walk test), muscle strength (Medical Research Council and maximum muscle strength tests), cardiovascular endurance and muscular endurance of the lower limbs at the fatigue threshold (physical working capacity at fatigue threshold) and quality of life (medical outcomes study SF-36 form). All tests were performed at baseline, after two weeks of treatment and at the end of the 4-week intervention period. RESULTS: Ergometer training and resistance training enhanced the effectiveness of standard care in order to improve (a) lower limb muscle strength, (b) walking ability and (c) cardiorespiratory fitness during inpatient rehabilitation of intensive care acquired weakness. In addition, ergometer training may be superior to resistance training. CONCLUSIONS: Our data encourage more research to develop and implement these training tools in rehabilitation programmes for intensive care acquired weakness.

Cortico-spinal excitability and hand motor recovery in stroke: a longitudinal study.

OBJECTIVE: To describe the relationship between changes of cortico-spinal excitability and motor recovery of the affected hand after stroke. METHODS: Eighteen hemiparetic stroke patients with a severe-to-mild upper limb motor impairment were randomized. Cortico-spinal excitability measures (resting motor thresholds and motor evoked potentials) obtained from a distal (abductor pollicis brevis) and proximal (biceps brachii) upper limb muscle were assessed for both hemispheres. Motor function of the affected hand was tested by the Wolf Motor Function and Action Research Arm tests. The evaluations were performed at baseline and weekly over 7 weeks of in-patient neurological rehabilitation. RESULTS: Severe hand dysfunction was associated with a strong suppression of ipsilesional cortico-spinal excitability and a shift of excitability towards the contralesional hemisphere. Mild hand impairment was associated with a shift of cortico-spinal excitability towards the ipsilesional hemisphere. Favorable motor recovery correlated with an increase of ipsilesional cortico-spinal excitability.

Motor Recovery of the Affected Hand in Subacute Stroke Correlates with Changes of Contralesional Cortical Hand Motor Representation.

Objective. To investigate the relationship between changes of cortical hand motor representation and motor recovery of the affected hand in subacute stroke. Methods. 17 patients with motor impairment of the affected hand were enrolled in an in-patient neurological rehabilitation program. Hand motor function tests (Wolf Motor Function Test, Action Research Arm Test) and neurophysiological evaluations (resting motor threshold, motor evoked potentials, motor map area size, motor map area volume, and motor map area location) were obtained from both hands and hemispheres at baseline and two, four, and six weeks of in-patient rehabilitation. Results. There was a wide spectrum of hand motor impairment at baseline and hand motor recovery over time. Hand motor function and recovery correlated significantly with (i) reduction of cortical excitability, (ii) reduction in size and volume of cortical hand motor representation, and (iii) a medial and anterior shift of the center of gravity of cortical hand motor representation within the contralesional hemisphere. Conclusion. Recovery of motor function of the affected hand after stroke is accompanied by definite changes in excitability, size, volume, and location of hand motor representation over the contralesional primary motor cortex. These measures may serve as surrogate markers for the outcome of hand motor rehabilitation after stroke.

Mapping cortical hand motor representation using TMS: A method to assess brain plasticity and a surrogate marker for recovery of function after stroke?

OBJECTIVE: Stroke is associated with reorganization within motor areas of both hemispheres. Mapping the cortical hand motor representation using transcranial magnetic stimulation may help to understand the relationship between motor cortex reorganization and motor recovery of the affected hand after stroke. METHODS: A standardized review of the pertinent literature was performed. RESULTS: We identified 20 trials, which analyzed the relationship between the extent and/or location of cortical hand motor representation using transcranial magnetic stimulation and motor function and recovery of the affected hand. Several correlations were found between cortical reorganization and measures of hand motor impairment and recovery. CONCLUSION: A better understanding of the relationships between the extent and location of cortical hand motor representation and the motor impairment and motor recovery of the affected hand after stroke may contribute to a targeted use of non-invasive brain stimulation protocols. In the future motor mapping may help to guide brain stimulation techniques to the most effective motor area in an affected individual.

Repetitive transcranial magnetic stimulation for motor recovery of the upper limb after stroke.

OBJECTIVE: Repetitive transcranial magnetic stimulation changes excitability of the motor cortex and it has hereby the potential to modulate changes in neural processing which impede motor recovery after stroke. METHODS: This chapter presents an up-to-day systematic review of the treatment effects of repetitive transcranial magnetic stimulation (rTMS) in promoting motor recovery of the affected upper limb after stroke. RESULTS: Thirty-seven trials were included in the analysis. The selected studies involved a total of 871 stroke subjects. All stimulation protocols pride on interhemispheric imbalance model. INTERPRETATION: rTMS enhances motor recovery of the affected hand after stroke; however, the data available until today is too limited to support its routine use.

The Effectiveness of 1 Hz rTMS Over the Primary Motor Area of the Unaffected Hemisphere to Improve Hand Function After Stroke Depends on Hemispheric Dominance.

OBJECTIVE: Inhibition of motor cortex excitability of the contralesional hemisphere may improve dexterity of the affected hand after stroke. METHODS: 40 patients (17 dominant hemispheric stroke, 23 non-dominant hemispheric stroke) with a mild to moderate upper limb motor impairment were enrolled in a double-blind, randomized, placebo-controlled trial with two parallel-groups. Both groups received 15 daily sessions of motor training preceded by either 1 Hz rTMS or sham rTMS. Behavioral and neurophysiological evaluations were performed at baseline, after the first week and after the third week of treatment, and after a 6 months follow-up. RESULTS: In both groups motor function of the affected hand improved significantly. Patients with stroke of the non-dominant hemisphere made a similar improvement, regardless of whether the motor training was preceded by sham or 1 Hz rTMS. Patients with stroke of the dominant hemisphere had a less favorable improvement than those with stroke of the non-dominant hemisphere after motor training preceded by sham rTMS. However, when 1 Hz rTMS preceded the motor training, patients with stroke of the dominant hemisphere made a similar improvement as those with stroke of the non-dominant hemisphere. INTERPRETATION: Motor recovery of the affected upper limb after stroke is determined by dominance of the affected hemisphere. Stroke of the dominant hemisphere is associated with per se poorer improvement of the affected hand. 1 Hz rTMS over the contralesional M1 significantly improves dexterity of the affected hand in patients with stroke of the dominant hemisphere, but not in those with stroke of the non-dominant hemisphere.

Transcranial direct current stimulation for motor recovery of upper limb function after stroke.

BACKROUND: Changes in neural processing after stroke have been postulated to impede recovery from stroke. Transcranial direct current stimulation has the potential to alter cortico-spinal excitability and thereby might be beneficial in stroke recovery. METHODS: We review the pertinent literature prior to 30/09/2013 on transcranial direct current stimulation in promoting motor recovery of the affected upper limb after stroke. RESULTS: We found overall 23 trials (they included 523 participants). All stimulation protocols pride on interhemispheric imbalance model. In a comparative approach, methodology and effectiveness of (a) facilitation of the affected hemisphere, (b) inhibition of the unaffected hemisphere and (c) combined application of transcranial direct current stimulation over the affected and unaffected hemispheres to treat impaired hand function after stroke are presented. CONCLUSIONS: Transcranial direct current stimulation is associated with improvement of the affected upper limb after stroke, but current evidence does not support its routine use.

1 Hz rTMS preconditioned by tDCS over the primary motor cortex in Parkinson's disease: effects on bradykinesia of arm and hand.

To investigate whether a period of 1 Hz repetitive transcranial magnetic stimulation (rTMS) over M1 preconditioned by tDCS improves bradykinesia of the upper limb in Parkinson's disease (PD). Fifteen patients with PD performed index finger, hand tapping and horizontal pointing movements as well as reach-to-grasp movements with either hand before (baseline conditions) and after a period of 1 Hz rTMS preconditioned by (1) sham, (2) anodal or (3) cathodal tDCS over the primary motor cortex contralateral to the more affected body side. Movement kinematics was analysed using an ultrasound-based motion analyser at baseline, immediately after and 30 min after each stimulation session. Dopaminergic medication was continued. Compared to baseline, 1 Hz rTMS significantly increased the frequency of index finger and hand tapping as well as horizontal pointing movements performed with the contralateral hand. Movement frequency increased up to 40% over 30 min after cessation of the stimulation. Preconditioning with cathodal tDCS, but not with anodal tDCS, reduced the effectiveness of 1 Hz rTMS to improve tapping and pointing movements. There was no significant increase of movement frequencies of the ipsilateral hand induced by 1 Hz rTMS preconditioned by either tDCS session. Movement kinematics of reach-to-grasp movements were not significantly influenced by either stimulation session. In PD the beneficial effects of 1 Hz rTMS over the primary motor cortex on bradykinesia of simple finger, hand and pointing movements is reduced by preconditioning with cathodal tDCS, but not with anodal tDCS. Preconditioning with tDCS is a powerful tool to modulate the behavioural effect of 1 Hz rTMS over the primary motor cortex in PD.