Transcranial DC Stimulation Benefits Primary Progressive Aphasia

Nancy A. Melville

October 24, 2016

BALTIMORE — Transcranial direct-current stimulation (tDCS) combined with a language intervention shows benefit in improving language rehabilitation in two types of primary progressive aphasia (PPA) for up to 2 months, new research suggests.

"Besides showing the potential of a new noninvasive technique, this study shows similar effects in patients with different probable pathologies, indicating that the mechanism by which tDCS works is not affected by the differential underlying disease pathology in the two PPA variants," the authors, from Johns Hopkins Medicine's Department of Neurology, Baltimore, Maryland, report.

Language skills deteriorate progressively with PPA, while other cognitive functions often remain unaffected in the early stages of this neurodegenerative syndrome. Pathologies in PPA span from Alzheimer's disease to tauopathies, typical to fronto-temporal dementia. As with stroke-related aphasia, however, no known effective treatments exist.

Previous research has shown encouraging effects of tDCS in improving language rehabilitation in stroke that last up to 6 months, and in a study published in the journal Aphasiology, the Johns Hopkins team also showed effects with PPA.

New research presented at the American Neurological Association (ANA) 2016 Annual Meeting extends on those findings, looking specifically at the effects of tDCS on the three variants of PPA: logopenic (lv), nonfluent (nfv), and semantic.

The first study involved 10 patients with lvPPA and 9 with nfvPPA who were treated with anodal tDCS or a sham treatment in a within-patients crossover design over 15 sessions.

Stimulation was targeted to the left hemisphere in the area of the left inferior frontal gyrus, considered to be involved in written language production, at a current of 2 mA for 20 minutes per session. All patients also received a spelling intervention therapy.

A comparison of evaluations before, immediately after, 2 weeks after, and 2 months after showed similar results in both groups, with each showing greater improvement with spelling therapy for untrained items after tDCS compared with sham (lvPPA, P = .03; nfvPPA, P = .01), and effects lasting up to 2 months, regardless of whether tDCS was provided during the first or second period of the study.

Similar findings were not seen in patients with semantic PPA; however, the improvements in spelling are nevertheless beneficial, senior author Kyrana Tsapkini, PhD, from the Department of Neurology at Johns Hopkins Medicine, told Medscape Medical News.

"Some of these patients even become mute at some point, so to even be able to improve at any level in communicating can be a help," she said.

"And it can also possibly help us offer better compensatory strategies, such as help with word retrieval, if patients lose their ability to communicate orally."

In a separate study involving 33 patients with PPA (18 with nfvPPA, 7 with lvPPA, and 8 with semantic PPA), Dr Tsapkini and her colleagues evaluated whether the tDCS treatment to the same left hemisphere area could also affect other language and cognitive functions.

A variety of measures were evaluated, including noun and verb naming, spatial span exercises, spelling tasks and letter fluency, sentence anagrams, and noun and verb semantics.

Improvements were found in tasks that had been practiced in therapy (as opposed to those not practiced), such as letter and semantic verbal fluency, compared with sham; however, the improvement was limited to therapy tasks.

In both studies, patients also showed some improvement even with the sham therapy because of the speech therapy that all received.

The findings of the statistically greater improvement in some measures with tDCS, though preliminary, are encouraging given the nature of the disorders, Dr Tsapkini said.

"These are primary progressive aphasia patients with different etiologies and this makes it very interesting because these are caused by degenerative diseases," she said.

"Because there is progressive deterioration, the effects due to tDCS may not be as long-lasting as with something like stroke, but the benefits still can be important."

In ongoing research, the authors plan to look at further issues in larger cohorts, including factors such as severity of disease, site of stimulation, age, and the effectiveness of different stimulation sites on language rehabilitation.

The studies received funding from the National Institutes of Health and Johns Hopkins University. Dr Tsapkini has disclosed no relevant financial relationships.

American Neurological Association (ANA) 2016 Annual Meeting. Abstracts M123 and M176. Presented October 18, 2016.

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