Lucinda S Chipchase

Peripheral electrical stimulation to induce cortical plasticity: A systematic review of stimulus parameters

Peripheral electrical stimulation (ES) is commonly used as an intervention to facilitate movement and relieve pain in a variety of conditions. It is widely accepted that ES induces rapid plastic change in the motor cortex. This leads to the exciting possibility that ES could be used to drive cortical plasticity in movement disorders, such as stroke, and conditions where pain affects motor control. This paper aimed to critically review the literature to determine which parameters induced cortical plasticity in healthy individuals using ES. A literature search located papers that assessed plasticity in the primary motor cortex of adult humans. Studies that evaluated plasticity using change in the amplitude of potentials evoked by transcranial magnetic stimulation of the motor cortex were included. Details from each study including sample size, ES parameters and reported findings were extracted and compared. Where data were available, Cohens standardised mean differences (SMD) were calculated. Nineteen studies were located. Of the parameters evaluated, variation of the intensity of peripheral ES appeared to have the most consistent effect on modulation of excitability of corticomotor pathway to stimulated muscles. There was a trend for stimulation above motor threshold to increase excitability (SMD 0.79 mV, CI -0.10 to 1.64). Stimulation below motor threshold, but sufficient to induce sensory perception, produced conflicting results. Further studies with consistent methodology and larger subject numbers are needed before definitive conclusions can be drawn. There also appeared to be a time effect. That is, longer periods of ES induced more sustained changes in cortical excitability. There is insufficient evidence to determine the effect of other stimulation parameters such as frequency and waveform. Further research is needed to confirm whether modulation of these parameters affects plastic change.

A checklist for assessing the methodological quality of studies using transcranial magnetic stimulation to study the motor system: An international consensus study

In the last decade transcranial magnetic stimulation (TMS) has been the subject of more than 20,000 original research articles. Despite this popularity, TMS responses are known to be highly variable and this variability can impact on interpretation of research findings. There are no guidelines regarding the factors that should be reported and/or controlled in TMS studies. This study aimed to develop a checklist to be recommended to evaluate the methodology and reporting of studies that use single or paired pulse TMS to study the motor system. A two round international web-based Delphi study was conducted. Panellists rated the importance of a number of subject, methodological and analytical factors to be reported and/or controlled in studies that use single or paired pulse TMS to study the motor system. Twenty-seven items for single pulse studies and 30 items for paired pulse studies were included in the final checklist. Eight items related to subjects (e.g. age, gender), 21 to methodology (e.g. coil type, stimulus intensity) and two to analysis (e.g. size of the unconditioned motor evoked potential). The checklist is recommended for inclusion when submitting manuscripts for publication to ensure transparency of reporting and could also be used to critically appraise previously published work. It is envisaged that factors could be added and deleted from the checklist on the basis of future research. Use of the TMS methodological checklist should improve the quality of data collection and reporting in TMS studies of the motor system.

Corticospinal excitability is dependent on the parameters of peripheral electric stimulation : a preliminary study

OBJECTIVE To evaluate the effect of 6 electric stimulation paradigms on corticospinal excitability. DESIGN Using a same subject pre-post test design, transcranial magnetic stimulation (TMS) was used to measure the responsiveness of corticomotor pathway to biceps and triceps brachii muscles before and after 30 minutes of electric stimulation over the biceps brachii. Six different electric stimulation paradigms were applied in random order, at least 3 days apart. SETTING Motor control research laboratory. PARTICIPANTS Healthy subjects (N=10; 5 women, 5 men; mean age ± SD, 26 ± 3.6y). INTERVENTIONS Six different electric stimulation paradigms with varied stimulus amplitude, frequency, and ramp settings. MAIN OUTCOME MEASURE Amplitudes of TMS-induced motor evoked potentials at biceps and triceps brachii normalized to maximal M-wave amplitudes. RESULTS Electric stimulation delivered at stimulus amplitude sufficient to evoke a sensory response at both 10 Hz and 100 Hz, and stimulus amplitude to create a noxious response at 10 Hz decreased corticomotor responsiveness (all P<0.01). Stimulation sufficient to induce a motor contraction (30 Hz) applied in a ramped pattern to mimic a voluntary activation increased corticomotor responsiveness (P=0.002), whereas constant low- and high-intensity motor stimulation at 10 Hz did not. Corticomotor excitability changes were similar for both the stimulated muscle and its antagonist. CONCLUSIONS Stimulus amplitude (intensity) and the nature (muscle flicker vs contraction) of motor stimulation have a significant impact on changes in corticospinal excitability induced by electric stimulation. Here, we demonstrate that peripheral electric stimulation at stimulus amplitude to create a sensory response reduces corticomotor responsiveness. Conversely, stimulus amplitude to create a motor response increases corticomotor responsiveness, but only the parameters that create a motor response that mimics a voluntary muscle contraction.

Primary Sensory and Motor Cortex Excitability Are Co- Modulated in Response to Peripheral Electrical Nerve Stimulation

Peripheral electrical stimulation (PES) is a common clinical technique known to induce changes in corticomotor excitability; PES applied to induce a tetanic motor contraction increases, and PES at sub-motor threshold (sensory) intensities decreases, corticomotor excitability. Understanding of the mechanisms underlying these opposite changes in corticomotor excitability remains elusive. Modulation of primary sensory cortex (S1) excitability could underlie altered corticomotor excitability with PES. Here we examined whether changes in primary sensory (S1) and motor (M1) cortex excitability follow the same time-course when PES is applied using identical stimulus parameters. Corticomotor excitability was measured using transcranial magnetic stimulation (TMS) and sensory cortex excitability using somatosensory evoked potentials (SEPs) before and after 30 min of PES to right abductor pollicis brevis (APB). Two PES paradigms were tested in separate sessions; PES sufficient to induce a tetanic motor contraction (30–50 Hz; strong motor intensity) and PES at sub motor-threshold intensity (100 Hz). PES applied to induce strong activation of APB increased the size of the N20-P25 component, thought to reflect sensory processing at cortical level, and increased corticomotor excitability. PES at sensory intensity decreased the size of the P25-N33 component and reduced corticomotor excitability. A positive correlation was observed between the changes in amplitude of the cortical SEP components and corticomotor excitability following sensory and motor PES. Sensory PES also increased the sub-cortical P14-N20 SEP component. These findings provide evidence that PES results in co-modulation of S1 and M1 excitability, possibly due to cortico-cortical projections between S1 and M1. This mechanism may underpin changes in corticomotor excitability in response to afferent input generated by PES.

Effects of whole body vibration on strength and functional mobility in multiple sclerosis

The aim of this study was to examine the effectiveness of regular whole body vibration (WBV) training on lower limb muscle strength and functional mobility in individuals with multiple sclerosis. A single subject experimental design was replicated on three subjects. Phases included a 4-week baseline phase without intervention, 6 weeks of twice weekly WBV intervention on a VibroGym apparatus, and a 4-week baseline phase without intervention. During all phases, strength of the ankle plantarflexors and knee extensors was assessed twice weekly with the Nicholas Manual Muscle tester and functional mobility with the Timed Up and Go test. All subjects improved significantly in plantarflexor strength (p<0.05). One subject improved significantly in knee extensor strength bilaterally and one subject in the weaker leg. Two subjects improved significantly in functional mobility. These improvements in strength and mobility were maintained in the final baseline phase. In conclusion, regular WBV training can improve lower limb strength and mobility in some individuals with multiple sclerosis. Individuals who do not perform any other exercise, are in a moderate stage of disease progression, and have a more intensive exercise protocol in conjunction with WBV seem to benefit most. However, further high-quality studies are needed.

Novel adaptations in motor cortical maps: the relation to persistent elbow pain.

INTRODUCTION Unilateral elbow pain results in sensorimotor dysfunction that is frequently bilateral, affects local and remote upper limb muscles, and persists beyond resolution of local tendon symptoms. These characteristics suggest supraspinal involvement. Here, we investigated 1) the excitability and organization of the M1 representation of the wrist extensor muscles and 2) the relation between M1 changes and clinical outcomes in lateral epicondylalgia (LE) (n = 11) and healthy control subjects (n = 11). METHODS Transcranial magnetic stimulation was used to map the M1 representation of the extensor carpi radialis brevis (ECRB) and extensor digitorum (ED). RESULTS The cortical representations of ECRB and ED were more excitable, and the centers of gravity for the two muscles were located closer together in LE than that in healthy controls. Increased ECRB excitability and closer location of the center of gravity were associated with higher pain severity at rest and/or in the preceding 6 months. A novel finding was a reduced number of discrete peaks in the representations of ECRB and ED in participants with LE compared with that in healthy controls. CONCLUSIONS This finding may have broad implications for the control of the wrist extensor muscles in LE. These data provide evidence that cortical organization may be maladaptive in LE and suggest that reorganization may be associated with persistence/recurrence of pain.

A national study of the availability and use of electrophysical agents by Australian physiotherapists

Electrophysical agents (EPAs) are a core part of physiotherapy practice and entry level education. With the increase in the number of EPAs over time, their availability and use in contemporary physiotherapy practice is an important consideration when determining entry level curricula. Thus, the aim of the study was to ascertain the current availability and usage of EPAs in Australian physiotherapy practice. A purpose-designed questionnaire was mailed to all registered physiotherapists in Australia. A response rate of 27% was obtained (n=3,538). Nonresponder analyses indicated that the results were representative of the total population of Australian physiotherapists. Over 70% of respondents had access to ultrasound, cold packs/ice, heat packs, electrical stimulation for sensory stimulation, and interferential therapy. Two main groups of EPAs were used relatively frequently. The first group was used daily or monthly by 60% of respondents (ultrasound, hot packs, and cold packs/ice), and a second group (electromyographic and pressure biofeedback, interferential therapy, and electrical stimulation for sensory stimulation) was used on a daily or monthly basis by between 30% and 45% of the sample. A group of EPAs, including ultraviolet light, microwave, and shortwave diathermy, was not used by over 90% of the sample. The study has provided contemporary national data on EPA availability and use in Australia.

Priming the brain to learn: The future of therapy?

Neuromodulatory techniques with the ability to alter cortical excitability are gaining interest for their potential to enhance the brains sensitivity to traditional therapies. Neuromodulatory techniques that prime the brain prior to manual or exercise therapy hold therapeutic promise for enhancing clinical outcomes in musculoskeletal and neurological conditions. The integration of these techniques into physiotherapy practice represents an exciting opportunity for the therapists of the future. Here, an overview is provided of three neuromodulatory techniques (peripheral electrical stimulation, transcranial direct current stimulation and repetitive transcranial magnetic stimulation) and the potential implications of these techniques for therapists discussed. Understanding these techniques and their therapeutic implications will ensure that therapists are well positioned to contribute to their clinical translation and adoption into clinical practice in an appropriate time frame. A therapeutic landscape defined by neuromodulatory techniques and improved clinical outcomes across a range of conditions is no longer far-fetched.

Characteristics of student preparedness for clinical learning: clinical educator perspectives using the Delphi approach

BackgroundDuring clinical placements, clinical educators facilitate student learning. Previous research has defined the skills, attitudes and practices that pertain to an ideal clinical educator. However, less attention has been paid to the role of student readiness in terms of foundational knowledge and attitudes at the commencement of practice education. Therefore, the aim of this study was to ascertain clinical educators’ views on the characteristics that they perceive demonstrate that a student is well prepared for clinical learning.MethodsA two round on-line Delphi study was conducted. The first questionnaire was emailed to a total of 636 expert clinical educators from the disciplines of occupational therapy, physiotherapy and speech pathology. Expert clinical educators were asked to describe the key characteristics that indicate a student is prepared for a clinical placement and ready to learn. Open-ended responses received from the first round were subject to a thematic analysis and resulted in six themes with 62 characteristics. In the second round, participants were asked to rate each characteristic on a 7 point Likert Scale.ResultsA total of 258 (40.56%) responded to the first round of the Delphi survey while 161 clinical educators completed the second (62.40% retention rate). Consensus was reached on 57 characteristics (six themes) using a cut off of greater than 70% positive respondents and an interquartile deviation IQD of equal or less than 1.ConclusionsThis study identified 57 characteristics (six themes) perceived by clinical educators as indicators of a student who is prepared and ready for clinical learning. A list of characteristics relating to behaviours has been compiled and could be provided to students to aid their preparation for clinical learning and to universities to incorporate within curricula. In addition, the list provides a platform for discussions by professional bodies about the role of placement education.

Interaction Between Simultaneously Applied Neuromodulatory Interventions in Humans

BACKGROUND Transcranial direct current stimulation (tDCS) is a neuromodulatory technique with the potential to enhance the efficacy of traditional therapies such as neuromuscular electrical stimulation (NMES). Yet, concurrent application of tDCS/NMES may also activate homeostatic mechanisms that block or reverse effects on corticomotor excitability. It is unknown how tDCS and NMES interact in the human primary motor cortex (M1) and whether effects are summative (increase corticomotor excitability beyond that of tDCS or NMES applied alone) or competitive (block or reduce corticomotor excitability effects of tDCS or NMES applied alone). OBJECTIVE To investigate corticomotor excitability in response to NMES after concurrent application of tDCS protocols that enhance (anodal tDCS) or suppress (cathodal tDCS) excitability of M1. METHODS We used transcranial magnetic stimulation (TMS) to examine corticomotor excitability before and after the concurrent application of: i) NMES with anodal tDCS; and ii) NMES with cathodal tDCS. Effects were contrasted to four control conditions: i) NMES alone, ii) anodal tDCS alone, iii) cathodal tDCS alone, and iv) sham stimulation. RESULTS Concurrent application of two protocols that enhance excitability when applied alone (NMES and anodal tDCS) failed to induce summative effects on corticomotor excitability, as predicted by homeostatic plasticity mechanisms. Combined cathodal tDCS and NMES suppressed the enhanced excitation induced by NMES, an effect that might be explained by calcium dependent anti-gating models. CONCLUSIONS These novel findings highlight the complex mechanisms involved when two neuromodulatory techniques are combined and suggest that careful testing of combined interventions is necessary before application in clinical contexts.