HAL® exoskeleton training improves walking parameters and normalizes cortical excitability in primary somatosensory cortex in spinal cord injury patients.

Matthias Sczesny-Kaiser,Martin Tegenthoff,Renate Meindl,Peter Schwenkreis,Thomas A Schildhauer,Mirko Aach,Oliver Höffken,Dennis Grasmücke,Oliver Cruciger

doi:10.1186/s12984-015-0058-9

Abstract

BackgroundReorganization in the sensorimotor cortex accompanied by increased excitability and enlarged body representations is a consequence of spinal cord injury (SCI). Robotic-assisted bodyweight supported treadmill training (BWSTT) was hypothesized to induce reorganization and improve walking function.ObjectiveTo assess whether BWSTT with hybrid assistive limb® (HAL®) exoskeleton affects cortical excitability in the primary somatosensory cortex (S1) in SCI patients, as measured by paired-pulse somatosensory evoked potentials (ppSEP) stimulated above the level of injury.MethodsEleven SCI patients took part in HAL® assisted BWSTT for 3 months. PpSEP were conducted before and after this training period, where the amplitude ratios (SEP amplitude following double pulses - SEP amplitude following single pulses) were assessed and compared to eleven healthy control subjects. To assess improvement in walking function, we used the 10-m walk test, timed-up-and-go test, the 6-min walk test, and the lower extremity motor score.ResultsPpSEPs were significantly increased in SCI patients as compared to controls at baseline. Following training, ppSEPs were increased from baseline and no longer significantly differed from controls. Walking parameters also showed significant improvements, yet there was no significant correlation between ppSEP measures and walking parameters.ConclusionsThe findings suggest that robotic-assisted BWSTT with HAL® in SCI patients is capable of inducing cortical plasticity following highly repetitive, active locomotive use of paretic legs. While there was no significant correlation of excitability with walking parameters, brain areas other than S1 might reflect improvement of walking functions. EEG and neuroimaging studies may provide further information about supraspinal plastic processes and foci in SCI rehabilitation.

Highlights

Reorganization in the sensorimotor cortex accompanied by increased excitability and enlarged body representations is a consequence of spinal cord injury (SCI)
The findings suggest that robotic-assisted bodyweight supported treadmill training (BWSTT) with HAL® in SCI patients is capable of inducing cortical plasticity following highly repetitive, active locomotive use of paretic legs
In contrast to other exoskeletons, HAL® exoskeleton (Cyberdyne Inc., Japan) offers the possibility of monitoring muscle contractions via surface EMG-electrodes at the extensor-flexor muscle region of the lower extremities [27, 28]. This allows for voluntary machine-supported motion using minimal signals recorded from hip and knee flexors and extensors. In both a pilot study and a single case study, we demonstrated that BWSTT with HAL® exoskeleton in SCI patients resulted in improved functional abilities for over-ground walking, as measured by the 10-m walk test (10MWT), 6-min walk test (6MWT) and timed-up-andgo test (TUG test) [28, 29]

Summary

Introduction

Reorganization in the sensorimotor cortex accompanied by increased excitability and enlarged body representations is a consequence of spinal cord injury (SCI). Functional magnetic resonance imaging (fMRI) studies in paraplegic patients support these results, showing an enlarged body representation with increased and a medially-shifted, i.e., towards the leg representation, activation maxima in cortical areas related to muscles proximal to the lesion [5, 6, 8, 10]. These changes likely reflect neuronal plastic mechanisms in the primary motor cortex (M1), which are necessary to adapt to physical impairments and to optimize walking abilities [11]. We investigated how HAL®-assisted BWSTT may alter both behavioral measures and S1 excitability in paraplegic SCI patients

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Discussion

Conclusion