Impact of Combined Transcranial Direct Current Stimulation and Speech-language Therapy on Spontaneous Speech in Aphasia: A Randomized Controlled Double-blind Study

Abstract

Objective:Aphasia recovery depends on neural reorganization, which can be enhanced by speech-language therapy and noninvasive brain stimulation. Several studies suggested that transcranial direct current stimulation (tDCS) associated with speech-language therapy may improve verbal performance evaluated by analytic tests, but none focused on spontaneous speech. We explored the effect of bihemispheric tDCS on spontaneous speech in patients with poststroke aphasia.Methods:In this multicentric controlled randomized cross-over double-blind study, we included 10 patients with poststroke aphasia (4 had aphasia >6 months and 6 with aphasia <6 months). We combined the sessions of speech-language therapy and bihemispheric tDCS (2 mA, 20 min). After three baseline speech evaluations (1/week), two different conditions were randomly consecutively proposed: active and sham tDCS over 3 weeks with 1 week of washout in between. The main outcome measure was the number of different nouns used in 2 min to answer the question “what is your job.”Results:There was no significant difference between conditions concerning the main outcome measure (p = .47) nor in the number of verbs, adjectives, adverbs, pronouns, repetitions, blank ideas, ideas, utterances with grammatical errors or paraphasias used. Other cognitive functions (verbal working memory, neglect, or verbal fluency) were not significantly improved in the tDCS group. No adverse events occurred.Conclusion:Our results differed from previous studies using tDCS to improve naming in patients with poststroke aphasia possibly due to bihemispheric stimulation, rarely used previously. The duration of the rehabilitation period was short given the linguistic complexity of the measure. This negative result should be confirmed by larger studies with ecological measures.

Transcranial Direct-Current Stimulation and Behavioral Training, a Promising Tool for a Tailor-Made Post-stroke Aphasia Rehabilitation: A Review

“…The studies here described included patients with different types of language impairments. Patients presented with both fluent and non-fluent aphasia, and in several cases anomia ( Vines et al, 2009 , 2011 ; Flöel et al, 2011 ; Fridriksson et al, 2011 , 2018b ; Richardson et al, 2015 ; Basat et al, 2016 ) or a deficit in spontaneous speech production ( Marangolo et al, 2014a ; Guillouët et al, 2020 ). Apraxia of speech was also often found ( Marangolo et al, 2011 , 2013a ; De Aguiar et al, 2015a ).…”

Innovative Approaches to Aphasia Rehabilitation: a Review on Efficacy, Safety and Controversies

“…Together with these two approaches, more recently, dual stimulation has been proposed in which the left and right hemisphere are simultaneously targeted with anodal and cathodal stimulation, respectively, to enhance activity into the left perilesional cortex [25,26,29,142]. Indeed, a very recent modeling study by Galletta et al [171] which compared the most used electrode montages in tDCS aphasia studies, has concluded that dual stimulation exerts the highest electric field magnitude over the left perilesional areas.…”

“…to their extreme heterogeneity [126]. The classical modular approach has been most often adopted, thus, positioning the active electrode either over the left Broca's area [19,21,[23][24][25][26][27][28][29][30]142,146,153,155,157,162,163,168], the left Wernicke's area [19,[21][22][23]28,30,149,150,164,165] or the right homologues [20,144,148,157,159,164,166,167]. Indeed, most of the research has proved that anodal stimulation over these areas combined with language therapy increases different aspects of language.…”

“…Finally, two studies have targeted the dorsolateral prefrontal cortex [152,20] As reported in Table 3, the studies were not homogeneous on the number of sessions included varying from one [147,152,155,154,163] to five [21][22][23][24][25][142][143][144]146,148,151,153,156,165,166,168] to fifteen sessions [26,149,150,159]. While, for current intensity there was a substantial agreement to use 1mA [19,[21][22][23][24][25]28,30,[144][145][146]149,150,152,154,158,160,161,164,…”

“…Since anomia is the most common symptom in aphasia, most crossover studies focused on word recovery by combining tDCS with naming task, from noun treatment [20][21][22][23]149,[154][155][156][157][158][161][162][163][164][165][166]168] to verb treatment [21,23,143,144,151,156,160,162]. tDCS has also been combined with repetition task [24][25][26]146], Melodic Intonation Therapy [159,167], and conversational therapy in order to enhance speech fluency [27][28][29][30]142,145].…”