Pauline Anderson

June 29, 2015

BERLIN, Germany — Combining brain stimulation with a challenging motor training task may improve poststroke rehabilitation, according to a new randomized, double-blind, crossover study.

The study showed that compared with sham stimulation, a single session of dual transcranial direct-current stimulation (dual-tDCS) enhanced skill retention and produced lasting increases in resting-state functional MRI functional connectivity (FC) in the somatomotor network of stroke patients.

Because FC is considered a potential surrogate marker of poststroke recovery, the study findings are promising for neuro-rehabilitation, lead author Professor Yves Vandermeeren, MD, PhD, Neurology Department, Université catholique de Louvain, Brussels, Belgium, told Medscape Medical News.

"It's possible that within the next 5 or 10 years, every rehabilitation session will start with the placement of some electrodes to focus brain function, with the aim of enhancing the effect of training."

But Dr Vandermeeren stressed that brain stimulation won't work if the exercise that stroke patients are performing is "just repetitive training" and that the task needs to be "complex" and "challenging" to patients.

The research was presented here at the first Congress of the European Academy of Neurology (EAN).

Disrupted Connectivity

Research on resting-state fMRI has shown that FC is disrupted in stroke patients. This connectivity, said Dr. Vandermeeren, correlates with recovery. Motor learning, too, plays a key role in poststroke neuro-rehabilitation. With repeated training, movements become faster and more accurate, he added.

The new study included 22 patients with chronic hemiparetic stroke (18 men and 4 women). They ranged in age from 45 to 82 years.

Fifteen patients had sustained a subcortical stroke, while the rest had had a cortical stroke. All had some difficulty with hand function.

Their modified Rankin Scale score ranged from 1 to 4. Their National Institutes of Health Stroke Scale score was 0 to 12.

After completing a baseline resting-state fMRI session, patients entered the randomized, double-blind, placebo-controlled, crossover phase of the study. In each of the two parts of the study, patients received real or sham dual tDCS, applied over 30 minutes, while they completed the motor skill learning task.

Designed by the researchers, the task involves moving a mouse across a circuit as fast and as accurately as possible. For some patients, their paretic hand had to be taped to the computer to carry out the task, said Dr Vandermeeren.

Sixteen of the patients performed the task in a supine position, and the other 6 did so in front of a computer.

A week later, the patients returned for the "retention" session. A run of resting-state fMRI was carried out at the beginning of the retention session in each of the two study sections.

Researchers quantified FC with whole-brain independent component analysis.

The study found that compared with sham treatment, dual-tDCS enhanced motor skill retention (8% vs 64% for sham; P = .0004).

From the ICA, there were no changes between baseline and sham sessions in the somatomotor network, whereas FC was increased 1 week after dual-tDCS compared with baseline (qFDR < 0.05; t(63)  = 4.15).

Dr. Vandermeeren emphasized that the task has to be challenging.

"It's not just repetitive movements, but training that requires the subject to be focused, with increasing difficulty, raising the attention of the subject, and providing feedback and rewards."

He predicted that within about a decade, noninvasive brain stimulation might be added to poststroke exercises to enhance the rehabilitation effects. "Maybe patients can recover faster; maybe they can recover better, and maybe for a longer time," he told the session audience. As a quip, he added "It's a little bit like aspirin; it's good for everything…so far."

In responding to a query from a delegate about whether the data were sufficiently strong to suggest that a single brain stimulation could produce lasting results, Dr Vandermeeren said this was the first time that researchers were able to observe such a long-term effect with a single session of dual tDCS. Most effects from previous research with a single stimulation bout have been short-term.

Encouraging Findings

Commenting on the findings for Medscape Medical News, Gereon Fink, MD, PhD, director, Department of Neurology, University Hospital Cologne, Germany, who co-chaired the session on neurotraumatology and rehabilitation, said that the study is encouraging to those in the field.

"Given the importance of promoting brain plasticity to ameliorate neurological deficits, the results are very promising but nevertheless need to be replicated before one can really judge whether or not the approach used here may represent the future of post-stroke rehab."

It's important to keep in mind, said Dr Fink, that despite multiple studies reporting positive neuromodulatory effects of transcranial magnetic stimulation (TMS) or TDCS, many studies failed to find significant effects.

"Thus, at present, current evidence does not support the routine use of rTMS [repetitive TMS] or TDCS for the treatment of stroke. Further trials with larger sample sizes are needed to determine suitable rTMS or TDCS protocols and the long-term functional outcome."

Dr Vandermeeren and Dr Fink have disclosed no relevant financial relationships.

Congress of the European Academy of Neurology (EAN). Abstract 01124 Presented June 20, 2015.

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