July/August 2012

Brain Stimulation to Improve Speech After Stroke

By Juliann Schaeffer
Aging Well
Vol. 5 No. 4 P. 8

Nearly 800,000 people will experience a new or recurrent stroke this year, according to the American Heart Association, and the number of people who are living with the after-effects of stroke or brain attack is 4 million. A small percentage of these patients will recover completely with minimal care, but many will require extensive rehabilitation to regain the cognitive functions that were lost during the stroke.

“One-third of stroke patients will have word-finding problems, known as aphasia, and being able to communicate and get their words back can be a long process,” says Dr Jenny Crinion, a neuroscientist and clinical speech and language therapist at University College London.

This process can take years and can be incredibly frustrating for patients, who inherently know how to communicate but can’t find a way to persuade their brains to translate their thoughts for them. Crinion says research suggests patients require around 100 hours of speech therapy to achieve a significant long-term improvement in speech, yet “in the UK, after patients are discharged from the hospital, they receive only eight to 12 hours of speech therapy from the National Health Service,” she says.

This dilemma drove Crinion to her latest research, which focuses on using a type of brain stimulation that, in tandem with traditional language therapy, has thus far shown promise in speeding this process for stroke patients.

What Is It?
The research focuses on transcranial direct current stimulation (tDCS), “a form of noninvasive neurostimulation that uses constant, low current delivered to the brain via small electrodes directly applied to the head,” says Crinion. This generates an electromagnetic field that modulates the activity of brain neurons, and Crinion says other research has suggested that this type of brain stimulation could aid learning.

“It has also been suggested that tDCS may help to stimulate parts of the language center that have been damaged and encourage a certain degree of recovery and repair,” she says. “In cognitive studies, tDCS has been used to change probabilistic learning in adults and to study working memory, so I wondered, could stimulating aphasic patients’ speech centers while they were training help boost the effects of treatment?”

Study Results
Crinion sought to answer that question—or at least advance it—with a study she is currently leading. To date, 13 participants with aphasia have completed it. She compared patients receiving 60 hours of behavioral therapy alone with those receiving behavioral therapy along with brain stimulation.

The preliminary results are promising. “Picture naming accuracy for the trained items improved by 55% in the [behavioral training only] group and by 92% in those getting real stimulation,” Crinion explains. “The data suggests that the training program alone makes patients 55% better at relearning words. But brain stimulation together with training pushes that figure to 92%.”

And the results so far appear to be lasting. “Three months later, the same volunteers who received the stimulation performed 82% better than they had performed before treatment, while those receiving [just behavioral therapy] held steady with a 55% improvement,” she says.

The researchers used functional MRI (fMRI) imaging while participants were naming pictures and during other behavioral tests to measure the technique’s effectiveness. Noting the importance of the electrodes’ placement, Crinion says other research has generally shown that the effects of tDCS tend to be restricted to the area directly under the electrodes.

“Indeed, our fMRI studies reveal that although tDCS has the most activating effect on the underlying cortex, it is the interaction with the ongoing network engaged in the behavioral task—in our case, speaking—that will predict its strongest brain and behavioral effects,” she says. “We were able to judge if tDCS had an effect by looking at how the brain’s activation changed after tDCS and also whether people could name more pictures more accurately and faster than before after the treatment.”

The feedback from patients receiving the brain stimulation has so far been positive, with most enjoying participating and some even noticing a difference in their overall speech. “It’s intense and tiring, but I think it’s been worth it,” noted one participant. “I think I find words more quickly and my speaking is more fluent, even with words I haven’t had therapy on.”

An Adjunct Therapy
Crinion’s quick to note, however, that brain stimulation on its own will do nothing to improve speech. It must work in tandem with speech therapy. “The stimulation doesn’t work in isolation. Whatever you’re practicing has to be the right thing, and you need to pair this with stimulation in the right bit of the brain,” she says.

The stimulation acts as a booster to the normal rehabilitation approach, she says, either improving patients’ overall outcome or requiring half the time normally necessary to recover.

“It’s not that the stimulation itself is somehow magically curing deficits; it is the pairing of the stimulation with the classical speech therapy practice that seems to work,” she adds.

Looking Ahead
The current approach has proven to be very well tolerated by participants, and Crinion notes that numerous studies have linked it with only rare and relatively minor adverse effects, “but we need more research to make sure this is also the case in patient populations,” she says. “That’s particularly important in patients who might be more prone to seizures anyway—for example, after a stroke.”

Another consideration related to safety dictates that patients undergoing tDCS should have no metallic implants near the electrodes, and Crinion notes that personnel conducting the brain stimulation need to be appropriately trained beforehand.

But don’t expect to be offering stroke patients this therapy option just yet. This research is still in its infancy, and Crinion says it will be a while before tDCS is suitable for clinical work. “Currently it is a research tool, and a lot has to be learned first about how and in whom this brain stimulation method will work.”

While its full potential remains to be explored, Crinion notes that the research performed so far shows promise for this type of brain stimulation as an adjunct to normal rehabilitation for speech therapy following stroke, and other studies are currently researching its possible role in stimulating better memory in Alzheimer’s patients.

According to Crinion, this research has already piqued manufacturers’ interest. “Due to its appeal as a potential treatment tool, some manufacturers are exploring mini tDCS kits for patients’ self-administration at home with stimulation dosages preprogrammed by their clinician,” she says.

— Juliann Schaeffer is an associate editor at Great Valley Publishing Company.