Non-invasive brain stimulation: a new frontier in the treatment of neurogenic speech-language disorders.

There is a growing body of evidence to support the use of non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) for the treatment of acquired speech and language disorders. The aim of the present paper is to review evidence to support the use of these procedures in the treatment of aphasia and dysarthria. Both TMS and tDCS are described in terms of their underlying principles and biophysics and their relative advantages and disadvantages for rehabilitation of acquired neurogenic communication disorders. Several studies have documented positive effects of inhibitory repetitive TMS (rTMS) to right Broca's area homologue on language recovery in non-fluent aphasia post-stroke. Improved language outcomes subsequent to high frequency rTMS applied to the lesioned hemisphere have also been documented. Similarly, therapeutic benefits have also been reported following tDCS, although the findings are less consistent than is the case with rTMS. Improved articulatory function and speech intelligibility has been noted in response to stimulation with excitatory rTMS in Parkinson's disease. It is suggested that the use of brain stimulation techniques in combination with more traditional therapies may represent the most innovative future approach to the treatment of acquired communication disorders.