The Effect of Transcranial Direct Current Stimulation and Speech Language Therapy to Improve Language Functioning in Arabic Speakers With Aphasia Post-Stroke

The current planned study is a prospective randomized double-blind, sham-controlled, two parallel-groups, polycentric, phase-I superiority type of trial.

Right-handed native Arabic-speaking patients with chronic aphasia post-stroke will be recruited from multiple in and outpatient rehabilitation centers in Saudi Arabia. All participants with aphasia that exceeds at least six months post onset with deficits in naming skills due to ischemic lesion or haemorrhage in the left cerebral hemisphere will be included. Aphasia type and severity will be determined using GACAT. The study protocol has been approved by the Institutional Review Board (IRB) of Imam Abdulrahman Bin Faisal University, Saudi Arabia (IAU-IRB -2020-03-112). Written consent forms will be obtained from all participants or from their family members. All study procedures will be conducted in accordance with the current version of Declaration of Helsinki.

All participants will complete three consecutive phases: (i) baseline assessment, (ii) interventions (Speech and Language Therapy (SLT) with real tDCS or sham tDCS, and (iii) outcome testing (GACAT test). During the first week, each participant will complete GACAT as the first round of the outcome measures as pre-testing before starting SLT. The participant then will complete six consecutive weeks of SLT accompanied with either real tDCS or sham tDCS. Each session starts with 20 minutes of tDCS followed by the SLT program. Once the combined therapeutic intervention is completed, the participant will complete round 2 of outcome testing GACAT. Aphasia assessments will include full implementation of eight subtests of GACAT, whenever possible. For illiterate individuals with aphasia, four to sex subtests will be implemented. SLT will be customized and tailored to the patients' needs based on baseline assessment. Naming ability will be evaluated during two baseline assessments using GACAT that includes a naming of objects, naming of actions, and word fluency (n = 58). The pictures will be presented in random order on a laptop computer split into six sets with short breaks in between. Patients will be asked to name each picture as accurately as possible. Responses will be recorded and subsequently analyzed based on the first valid response. The first up to thirty pictures that will not be named correctly during both assessments will be selected for each patient and trained during therapy (trained items). Those items only comprised non responses, unrelated semantic errors, phonologically unrelated errors and neologisms. Minor articulatory errors due to mild apraxia of speech will not be scored as errors during any of the assessments. The purpose of speech therapy sessions will be to have the participant generate nouns and verbs in written and verbal forms. The remaining pictures, except correct responses, will be used to choose another 30 items (untrained items) and serve to assess transfer effects, these may include: omissions, semantic and phonemic paraphasias and other utterances. All stimuli that will be chosen for trained and untrained items are controlled for factors impacting processing: "response latency; name agreement; familiarity; age of acquisition; imageability, concreteness, image and name agreement, visual complexity, frequency, number of phonemes and syllables" .

The focus of SLT sessions will be on word retrieval and word-finding therapy whether nouns or verbs. SLT will be combined either with real tDCS in interventional group or sham tDCS in the control group. The SLT is provided by qualified clinicians with more than five years of experience in assessing and treating speech and language disorders post-stroke. The SLT will include word retrieval therapies that focus on phonological and semantic cueing treatments (PCT and SCT respectively) of nouns and verbs (action naming). The action-naming treatment is a typical hierarchical cueing approach, in which initially minimal cues are increased in a gradual basis until object action picture is named correctly. The verb-action therapy will combine production of verbs with gestural facilitation as verb deficits may stem from a deficit in semantic knowledge of actions caused by motor cortex damage. Therefore, gestures can provide some semantic redundancy, which has been lost in the training that focuses on verb production only. This treatment approach is in line with neuropsychological literature that shows the fact that verbs may demand more processing control than nouns because verbs require more executive resources and have lower imageability scores. Therefore, gestural facilitation may add more value for verb retrieval as it provides a form of additional constraint on activating the correct verb meaning. Patients may attend physical and occupational therapy sessions during the six-week treatment period but no other forms of speech therapy will be received during treatment period.

The frequency and intensity of treatment will be 90 minutes daily sessions for six consecutive weeks, results in 7.5 hours per week and total dosage of 45 hours throughout the course, which previously reported to be effective.