Monitoring Changes in TMS-Evoked EEG and EMG Activity During 1†Hz rTMS of the Healthy Motor Cortex.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique capable of inducing neuroplasticity as measured by changes in peripheral muscle electromyography (EMG) or electroencephalography (EEG) from pre-to-post stimulation. However, temporal courses of neuromodulation during ongoing rTMS are unclear. Monitoring cortical dynamics via TMS-evoked responses using EMG (motor-evoked potentials; MEPs) and EEG (transcranial-evoked potentials; TEPs) during rTMS might provide further essential insights into its mode of action - temporal course of potential modulations. The objective of this study was to first evaluate the validity of online rTMS-EEG and rTMS-EMG analyses, and second to scrutinize the temporal changes of TEPs and MEPs during rTMS. As rTMS is subject to high inter-individual effect variability, we aimed for single-subject analyses of EEG changes during rTMS. Ten healthy human participants were stimulated with 1,000 pulses of 1 Hz rTMS over the motor cortex, while EEG and EMG were recorded continuously. Validity of MEPs and TEPs measured during rTMS was assessed in sensor and source space. Electrophysiological changes during rTMS were evaluated with model fitting approaches on a group- and single-subject level. TEPs and MEPs appearance during rTMS was consistent with past findings of single pulse experiments. Heterogeneous temporal progressions, fluctuations or saturation effects of brain activity were observed during rTMS depending on the TEP component. Overall, global brain activity increased over the course of stimulation. Single-subject analysis revealed inter-individual temporal courses of global brain activity. The present findings are in favor of dose-response considerations and attempts in personalization of rTMS protocols.

Semi-automated motor hotspot search (SAMHS): a framework toward an optimised approach for motor hotspot identification.

Background: Motor hotspot identification represents the first step in the determination of the motor threshold and is the basis for the specification of stimulation intensity used for various Transcranial Magnetic Stimulation (TMS) applications. The level of experimenters' experience and the methodology of motor hotspot identification differ between laboratories. The need for an optimized and time-efficient technique for motor hotspot identification is therefore substantial. Objective: With the current work, we present a framework for an optimized and time-efficient semi-automated motor hotspot search (SAMHS) technique utilizing a neuronavigated robot-assisted TMS system (TMS-cobot). Furthermore, we aim to test its practicality and accuracy by a comparison with a manual motor hotspot identification method. Method: A total of 32 participants took part in this dual-center study. At both study centers, participants underwent manual hotspot search (MHS) with an experienced TMS researcher, and the novel SAMHS procedure with a TMS-cobot (hereafter, called cobot hotspot search, CHS) in a randomized order. Resting motor threshold (RMT), and stimulus intensity to produce 1 mV (SI1mV) peak-to-peak of motor-evoked potential (MEP), as well as MEPs with 120% RMT and SI1mV were recorded as outcome measures for comparison. Results: Compared to the MHS method, the CHS produced lower RMT, lower SI1mV and a trend-wise higher peak-to-peak MEP amplitude in stimulations with SI1mV. The duration of the CHS procedure was longer than that of the MHS (15.60 vs. 2.43 min on average). However, accuracy of the hotspot was higher for the CHS compared to the MHS. Conclusions: The SAMHS procedure introduces an optimized motor hotspot determination system that is easy to use, and strikes a fairly good balance between accuracy and speed. This new procedure can thus be deplored by experienced as well as beginner-level TMS researchers.

The Ability to Run in Young People with Cerebral Palsy before and after Single Event Multi-Level Surgery.

The objective of the study is to identify and evaluate possible factors that influence the ability to run before and after single event multi-level surgery (SEMLS). Young patients (6-25 years) with spastic cerebral palsy (GMFCSI-II) were retrospectively included. Type and number of surgical procedures, time for recovery and 3D gait analysis variables were analyzed with respect to the ability to run. In total, 98 patients (38 females; 60 males) who received SEMLS (12 years, SD 3.4) were included and compared to a control group of 71 conservatively treated patients. Of 60 runners pre-surgery, 17 (28%) lost the ability, while gained in 8 of 38 (21%) non-runners. The number of surgical procedures was a significant predictor and those who lost their ability to run had significantly more (mean = 5.9, SD = 1.7), compared to the patients who gained the ability (mean = 3.5, SD = 0.9). Further, pre-surgical function (e.g., gait speed) was significantly different (p < 0.001). Pre-surgical function and the number of surgical procedures seem to play an important role for the gain or loss of the ability to run after surgery. Caution is warranted in patients with lower pre-surgical function and the ability to run, as they seem at a higher risk to lose the ability.

Dynamic stability in cerebral palsy during walking and running: Predictors and regulation strategies.

BACKGROUND: The postural control in cerebral palsy (CP) is often deficient and manifests in a variety of impairments. Consequently, maintaining balance and controlling posture is impeded and results in an increased cost of locomotion and higher risk of falls. The margin of stability is an established measure to quantify dynamic stability during gait. It can be facilitated to analyze impaired control mechanisms, but it is unknown if and how people with CP manage to control the margin of stability during a more demanding motor task, such as running. RESEARCH QUESTION: How do people with cerebral palsy regulate dynamic stability during walking and running? METHODS: Children and adolescents with bilateral cerebral palsy (N = 117; 50 female, 67 male; age 11.0 ± 3.2) were retrospectively included. All underwent instrumented 3D gait analysis, walking and running barefoot at a self-selected gait speed. People with CP were compared to a control group of N = 25 typically developed (TD). Repeated measures ANOVAs were computed to analyze group differences and multiple linear regressions to identify predictors for the medio-lateral margin of stability. RESULTS: The medio-lateral margin of stability was significantly higher in the CP group and was statistically unchanged during running. Different adaptions when running were particularly observed in the lateral trunk lean and step width, which remained high in CP, whereas the TD increased the trunk lean and reduced their step width. Step width was the main predictor for the medio-lateral margin of stability in both gait conditions. SIGNIFICANCE: Young people with cerebral palsy manage to maintain their medio-lateral margin of stability during walking and running, however, with significantly higher safety margins compared to typically developed. This conservative strategy may reflect an adaption to motor and postural control impairments.

Compensatory mechanisms in children with idiopathic lower extremity internal rotational malalignment during walking and running.

BACKGROUND: Noticeable in-toeing gait is present in most children with internal rotational malalignment and often a reason to consult an orthopedic specialist. The risk of tripping may be higher for these patients. RESEARCH QUESTION: The aim of this study was to determine compensatory mechanisms adopted by children with internal rotational deformities to avoid tripping and falling during walking and running. METHODS: Sixty-nine patients between 5-18 years with idiopathic internal rotational malalignment were retrospectively included and subdivided into three groups: 18 patients with internal tibial torsion (ITT), 25 patients with internal femoral torsion (ITF) and 26 patients with both (ITB). Twenty-two typically developing age-matched children (TD) were analyzed for comparison. Three-dimensional gait data were evaluated. ANOVA's on two factors, group (ITT, ITF, ITB, TD) and movement (walking, running) with post-hoc t-tests were used to identify significant differences between groups. RESULTS: All groups had significantly greater step width than TD during walking (P ≤ .002) and all torsional groups had significantly greater step width during running (P ≤ .001). Similarly, all torsional groups showed greater peak ankle dorsiflexion in swing during running than TD (P ≤ .006). Only the ITT group showed significantly greater external hip rotation than TD. When compared to TD, the ITF and ITB group had a significantly lower hip abduction moment in stance during running, but not for walking (P ≤ .032). SIGNIFICANCE: Compensatory mechanisms in children with internal rotational deformities were mostly dependent on the location of rotational malalignment. All children with internal rotational malalignment had greater ankle dorsiflexion and greater step width during running. Especially in active patients, this greater ankle dorsiflexion during running may result in overuse of the ankle dorsiflexor muscles, while greater step width may have beneficial effects in normalizing knee adduction moments.

Excessive Lateral Trunk Lean in Patients With Cerebral Palsy: Is It Based on a Kinematic Compensatory Mechanism?

Introduction: Excessive lateral trunk lean is a commonly observed gait deviation in children with cerebral palsy (CP), with implications for energy expenditure and the development of back pain. While the trunk lean toward the stance leg is widely interpreted as a compensatory strategy to unload the hip, in CP the relation to hip abductor muscle strength is only weak. Therefore, other mechanisms may play a role in the prevalence of excessive trunk lean in CP, or it could be a primary motor function deficit. Research Question: Is the excessive lateral trunk lean in patients with CP part of an underlying biomechanical mechanism? Materials and Methods: Patients with bilateral CP (N = 255; age 13.6 ± 6.6 years) were retrospectively included and divided into a group with (n = 174) and without (n = 81) excessive lateral trunk lean. Ten lower-extremity joint angle waveforms were analyzed using a principal component analysis (PCA) to identify patterns of correlated deviations from average angle waveforms. Binary logistic regressions were performed to determine the discriminative capacity of the identified patterns. Results: The PCA identified correlated kinematic patterns, with lower-order patterns showing more common gait pathologies, such as torsional malalignments and crouch gait pattern. Within five patterns, significant (p < 0.0025) group differences were identified. Interestingly, the trunk lean was not always distinctive in these patterns and despite the significant differences their effect sizes were small. The logistic regression was unable to reliably classify patients based on their trunk lean patterns. Discussion: The current study identified multiple trunk lean-related patterns, however, excessive trunk lean was not attributable to a distinctive CP related gait pathology or to a specific compensatory strategy. Overall, the results do not support the hypothesis that excessive trunk lean is part of a biomechanical mechanism. Therefore, it seems more likely that excessive lateral trunk lean is based on other disease specific dysfunctions, influenced by the severity of the disease.

Cluster analysis to identify foot motion patterns in children with flexible flatfeet using gait analysis-A statistical approach to detect decompensated pathology?

INTRODUCTION: The paediatric flexible flatfoot constitutes the major cause of clinic visits for orthopaedic foot problems. It shows variations of deformities in different planes and locations of the foot and its indication for treatment have been extensively discussed. Despite its high prevalence there exists no classification of flatfeet during walking as a prerequisite for treatment decision. Therefore, the aim of this study is to classify flexible flatfeet based on 3D foot kinematics during walking. METHODS: Patients age 7-17 years with flexible flatfeet (N = 129, 255 feet) of non-neurogenic or syndromic origin, were retrospectively included. Patients underwent gait analysis using the Oxford Foot Model after standard clinical examination. A k-means cluster analysis was performed on 3 scores derived from the principal component analysis of the foot kinematic waveforms over the gait cycle. Gait and clinical parameters were then statistically tested between clusters. RESULTS: Cluster analysis revealed two groups of flexible flatfeet that were discriminated best by the inversion at push-off during walking. Cluster 2, including 110 feet, showed an average eversion instead of an inversion at push-off and a lower number of heel rises in the clinical test. Both was significantly different between clusters (p < 0.001). DISCUSSION: Based on the findings, the resultant clusters can be interpreted as describing compensated and decompensated feet, with the latter presenting a group that may require surgical interventions, even if they are not yet present with pain. The hindfoot inversion capability at push-off is the most important variable in the 3D gait analysis to classify flexible flat feet.

Prevalence and predictors for the ability to run in children and adolescents with cerebral palsy.

BACKGROUND: Running is a fundamental movement skill and a prerequisite for children to participate in numerous daily activities. The prevalence of the ability to run in people with Cerebral Palsy and the role of their impairments on running ability are unknown. Therefore, the aim of this study is to determine the prevalence of the ability to run and to identify contributing factors. METHODS: In this study, 280 children and adolescents with spastic Cerebral Palsy, Gross Motor Function Classification System level II were included. The ability to run was defined by instrumented running analysis. Runners and non-runners were compared regarding their clinical measures of spasticity, weakness, and postural control. Logistic regression was applied to identify the most important predictors for the ability to run. FINDINGS: The ability to run was significantly higher in unilateral (67%) than in bilateral (55%) affected patients. Significant differences between runners and non-runners were found for spasticity, BMI and postural control, but not for muscle strength. Lower M. rectus femoris spasticity, higher m gastrocnemius spasticity and enhanced postural control appear to be the best predictors for being able to run. INTERPRETATION: Patients with Gross Motor Function Classification System level II represent a large group in the gait laboratory and the functional impairment within this group differs greatly. Therefore, for clinical decision making we suggest to separate patients in this group based on their running ability. Spasticity and postural control affect the ability to run and needs to be accounted for in intervention programs.