The Combined Use of Transcranial Direct Current Stimulation and Robotic Therapy for the Upper Limb

Neurological disorders such as stroke, cerebral palsy and traumatic brain injury, are leading causes of long term instability reducing a patient's quality of life. Motor recovery is driven by neuroplasticity. Thus, rehabilitation therapies are strongly based on high dose, intensive training, and intense repetition of movements as to allow the recovery of strength and range of motion.

The advent of robot assistive therapy has been shown of great value to the rehabilitation, influencing process of neuroplasticity and heregonization. The most important advantage of using robot technology and rehabilitation intervention is the ability to deliver high dosage and high intensity training which otherwise would be a very labor-intensive process. It also allows an immediate perception and evaluation of motor recovery, and can also turn repetitive actions into meaningful interactive functional tasks.

Another new technique being developed for rehabilitation is the tDCS, which is the shorter for transcranial direct current stimulation. tDCS is a low-evasive brain stimulation technique which allows the changes in current excitability through the use of low-intensity electrical cortical stimulation applied over this count. tDCS, transcranial direct current stimulation, has generated much attention lately from researchers and also clinicians.

There are several reasons to explain. The main reason is due to its effects on neuroplasticity, and the other reasons are because tDCS device is cheap and also because tDCS is an easy technique to use. tDCS has been studied for several types of diseases, such as epilepsy, Parkinson's, depression and stroke.

However, tDCS is unlikely optimal for functional recovery on its own, but it is showing increasing promise as an adjunct therapy in rehabilitation as it enhances brain plasticity. Most studies involving robotic therapies or tDCS use them isolated. Few studies were done combining both of them which could possibly enhance their beneficial effects beyond each intervention alone.

These few small trials demonstrated a possible synergistic effect between these two procedures with improved motor recovery and functional ability. In this video, we describe the combined methods used in our institute for improving motor performance after stroke. tDCS can be used either before or during robotic rehabilitation as demonstrated in the medical literature.

Equipments needed:tDCS device, cables, rubber bands, sponges, sodium chloride solution, measuring tape, electrodes, battery. The stimulation location will be found through the measurement of scalp. Using the convention of the EEG 10/20 system, as described in our previous article.

In this protocol, we will stimulate the primary motor cortex, or M1.To locate this point, calculate 20%of the auricular measurement. This spot should correspond to C3/C4 EEG location. Place the electrode on the center of this spot, and the secondary electrode over the contralateral super orbital region.

After preparing the skin and localizing the stimulation site, After tDCS, refer patients to undergo robotic therapy. In this protocol, we will describe the use of the commercial of the MIT-Manus and T-WREX. The robot has several therapy protocols, allowing patients to practice motor-planning, eye-hand coordination, attention and mass practice.

The therapeutic exercises and games practice both wrist flexion and extension, along with radial and ulnar deviation. The video screen shows cues of the tasks that the subject needs to perform and constantly gives feedback of the position of the arm. On a robotic therapy session, the therapist selects the appropriate treatment protocol and the robot may provide real-time assistance if necessary.

The MIT-Manus arm allows the training of the elbow flexion and extension, shoulder protraction and retraction, and shoulder internal and external rotation on a horizontal plane. The robot will only assist the patient if necessary. For example, if the subject cannot realize the intended movement within two seconds, the machine will help complete its movement.

If the subject has not enough motor coordination to carry out the intended movement, the robot will guide the subject's arm to do the appropriate movement. The robot software has several therapeutic exercise games for motor training. The visual feedback usually consists in a yellow ball that the patient must move between targets.

Other training scenarios are available. The T-WREX consists of an exoskeleton that fits the subject's arm and allows him to move his shoulder, elbow, and wrist joints freely in a tri-dimensional setting. The adjustable mechanical arm allows variable levels of gravity support by means of a spring mechanism, enabling patients with residual upper limb function to achieve a larger active range of motion.

The compensation for the arm goes from A to I and A to E for the forearm. It consists of a linear scale of gravity support where A has no gravity support. Therapy protocols and games included allows the training of task-specific functions by moving the exoskeleton across a 3D workspace.

By combining movements of the shoulder, forearm, elbow, and wrist, the robot allows a task-specific repetitive training. A training session usually lasts about 60 minutes. In each session, the individual performs about 72 repetitions of the movement towards different functional targets.

Between each movement, allow a 10-second interval in order to prevent fatigue. The robots demonstrated on this video can be used as part of the rehabilitative program for several neurological injuries, including stroke, cerebral palsy, and spinal cord injury. They offer the ability of even severely impaired users to train independently and benefit from highly intensive repetitive and self-initiated movement therapy with increased user motivation.

Non-invasive brain stimulation with tDCS has generated much interest recently due its potential neuroplasticity effects, comparatively inexpensive equipment, ease of use, and few side effects. Studies have shown that neuromodulation with tDCS has the potential to modulate cortical excitablity and plasticity, thus promoting additional improvements in motor performance through long-term potentiation by stimulating the primary motor cortex. Previous studies have reported electrophysiological effects of tDCS lasting up to 90 minutes, and behavioral effects lasting up to 30 minutes after a single tDCS session of 20 minutes.

The evidence is still, however, controversial, as the positive findings are not consistent. A previous trial found functional motor improvement after bihemispheric stimulation that outlasted the intervention period. The evidence for robotic therapy in rehabilitation is more prominent, demonstrating clear incremental reductions of motor impairment.

However, due to the large number of manufacturers and several types of robotic devices, each machine has their own properties, qualities and limitations. A multi-center, randomized controlled trial found that chronic stroke patients with moderate to severe upper limb impairment had significant but modest improvement in arm function, movement, and quality of life after robotic training over the 36-week study period as compared to usual care, but not with intensive physical therapy. While trials of neurorehabilitation with separate tDCS or robotic therapies have been done before, few trials were conducted combining these therapies.

A previous trial evaluated the dimension of timing in combined robotic therapy with tDCS for wrist rehabilitation in chronic stroke patients. The authors found that wrist movement speed and smoothness was improved over 15%when tDCS was delivered prior to a 20-minute session of robotic training. The present paper aimed to describe a standard therapy protocol for combined noninvasive brain stimulation and robot-assisted movement therapy, used as an adjunct to conventional therapy, in patients with deficits in arm function in order to improve motor skill.

tDCS and robotics show significant motor effects but most of these studies show these effects when these techniques are used in isolation. What is important to explore is when we combine these two techniques it is possible to enhance their effects on more recovery. Robotic therapy endues an increase of cortical excitability in the brain and an increase of afferent input to the brain.

These combined with tDCS may result in a better motor outcome due to the synergetic effect of those therapies combined.