Effect of trans-spinal direct current stimulation and robotic support on the neural motor pathways in healthy and SCI subjects.

Spinal Cord Injury (SCI) is usually a severe injury to the pathways of the
central nervous system (CNS) in the spinal cord. Depending on where the injury
occurs, patients are often bound to a wheelchair or left with other impairments
diminishing their quality of life, despite a heavy post injury physical
rehabilitation regime. Trans-spinal direct current stimulation (tsDCS) and
robotic gait therapy are two promising new techniques under investigation for
the treatment of SCI. TsDCS is aiming to alter the response of the neural
pathways the stimulus is applied to. The resulting alteration of neural
activity in the spinal cord is hypothesized to have a positive effect on the
recovery of the damaged spinal cord neurons.
Similarly, robotic gait therapy is hypothesized to have a positive effect on
the cortico-spinal pathways by increasing the task specific intensity and
thereby aiding activity dependent plastic in the CNS.

The primary objective is to assess the neural short term changes, robotic gait
therapy and tsDCS have on the corticospinal pathways. Thereby it has to be
investigated in what kind of configuration and intensity tsDCS is most
effective as well as what kind of control scheme is most effective when using
more or less walking assistance during robotic walking assistance with the
LOPES II exoskeleton.

The overall goal is to perform all studies as randomized double blind
controlled trials.

For each experiment in this study, subjects will receive either tsDCS or
robotic therapy as an intervention. Possible is also a combination of both
techniques.
tsDCS is applied to the lumbar spinal cord for a period of maximum 15 minutes.
Stimulation amplitude may vary from zero to five milliamperes, with variable
electrode configurations on the back of the subject by using up to five
individual electrodes over which the applied current is divided.
Robotic therapy is applied using the LOPES exoskeleton. Thereby the subject is
aided in his effort to execute stepping movements on a treadmill.

Both, tsDCS and robotic therapy are non-invasive. tsDCS involves the electrical
stimulation of living tissue and therefore guidelines have to be followed for
the safe use of the technique. Two factors which are vital in this respect are
the overall current input into the tissue as well as the current density. Both
of these factors are limited by current strength and stimulation time. All in
all the application of tsDCS within the established limits can considered to
be safe with a minimum side effects.
During robotics therapy the subject is attached to the LOPES II exoskeleton,
which is able to support the person in his effort to make stepping movements.
The subject is thereby attached to the device via Velcro straps and secured by
a safety harness to prevent falling. During, before and after operation all
measures have been taken which ensures safe operation of the device which is
supported by previous studies the LOPES I has been part of. Additional
information concerning the LOPES II safety can be found in section 6.1. of C1.
In addition to the safety of both interventions alone, the combination of both
interventions is not thought to result into any harmful effects.
Patient benefit is closely related to the duration and effect of the
intervention. Thereby tsDCS produces an effect that may last up to several
hours of the treatment but decline subsequently. In terms of robotic therapy it
is not known to which extend there are longer lasting post treatment effects.
Since it however merely involves an intensified movement training, it is not
likely that any visible lasting abnormal will occur. Out if this reason subject
benefit for both interventions will be unlikely.
In terms of group relatedness, the specific application to SCI the study
depends on the participation of spinal cord injured subjects to a great extent.
It is therefore vital that SCI patients will be able to participate.