Effects of Neuronavigated Theta Burst Stimulation in Therapy of Post-stroke Aphasia

Effects of Neuronavigated Theta Burst Stimulation in Therapy of Post-stroke Aphasia

Aphasia is an impairment in the ability to express and/or understand language, commonly observed after stroke to the language dominant (left) hemisphere. Despite natural tendency to spontaneous functional recovery in the first months post stroke and language improvement due to application of behavioral speech and language therapy (SLT), many aphasic patients do not achieve satisfactory level of verbal communication. The aim of the planned study is to explore the potential of the noninvasive repetitive Transcranial Magnetic Stimulation (rTMS) as a therapeutic tool for aphasia in addition to traditional behavioral therapy. In case of aphasia, studies on therapeutic effectiveness of rTMS aim to increase the activity of the language-dominant left cerebral hemisphere, which may be achieved in an indirect manner by inhibiting the activity of the opposite (right) hemisphere or in a direct manner by increasing the excitability of preserved language areas in the left hemisphere. In our study, we plan to administer the newest form of rTMS called Theta Burst Stimulation (TBS), which is safer than the conventional rTMS, even when used in the perilesional area. Computer-based neuronavigation system will be implemented to precisely localize stimulation targets, control administration of stimuli during rTMS sessions, and evaluate differences between participants regarding deviations from established stimulation points. 45 patients (all right-handed, polish native speakers, aged 18-75 years, diagnosed with non-fluent aphasia) will be enrolled in a randomized, double-blind, sham-controlled trial. Subjects will be randomly assigned to one of the three groups: 1) a group with excitatory intermittent TBS of the left hemisphere (iTBS group), 2) a group with inhibitory continuous TBS of the right hemisphere (cTBS group), 3) a group with sham TBS (sTBS group as a control group). Specific forms of stimulation will be carried out for three consecutive weeks (Monday to Friday; a total of 15 stimulation sessions). Immediately after each session of the stimulation, patients will undergo individual SLT. Assessment of language functioning will be carried out three times: before and after the therapy period, and 3 months after its completion. Results of the study will broaden knowledge about hemispherical mechanisms of language and speech recovery after stroke and provide insight into possibilities of their modulation for the purpose of post-stroke rehabilitation.

Inclusion Criteria:

• First-ever left middle cerebral artery ischemic stroke (brain damage localization confirmed by magnetic resonance imaging, MRI)
• 3 or more months from the onset of stroke
• Non-fluent aphasia (confirmed in the BDAE test) with functional communication difficulties ranging from mild to significant (grades from 2 to 4 in ASRS), marked difficulties in naming, and relatively preserved everyday speech comprehension
• Native Polish speaker
• Right-handedness prior to stroke
• Signing of the informed consent for the participation in the study.

Exclusion Criteria:

• Psychiatric and/or neurological comorbidity (e. g. dementia, depressive disorder, alcohol dependence)
• Diagnose of epilepsy or epileptic changes in EEG, also frequent losses of consciousness of unclear etiology which might suggest epileptic seizures
• History of any neurosurgical procedure around the head area
• 1.5 T MRI examination contraindications (metal elements in the body, e. g. implantable cardioverter-defibrillator, deep brain stimulation devices; claustrophobia)
• Regular intake of medication that could affect cortical excitability (e. g. antiepileptic or antipsychotic drugs, antidepressants, benzodiazepines) or medication influencing neuroplastic processes (e. g. dopamine)
• Significant cognitive impairment limiting patient's cooperation during assessment and behavioral aphasia therapy
• Visual deficits significantly hindering the perception of therapeutic tasks presented visually on a computer's screen
• New neurological episode (e. g. another brain stroke) or somatic illness (e. g. COVID-19) during the cycle of the therapy, requiring its interruption.