TDCS and Aphasia Therapy in the Chronic Phase After Stroke

Aphasia is present in about one third of all stroke patients in the chronic phase. The first few months after stroke, considerable spontaneous recovery is initiated, including neuronal plasticity and reorganization processes. Language recovery in aphasic stroke patients involves reorganization of brain functions. Longitudinal fMRI studies reveal that the right hemisphere shows increased activity at different times in the recovery process, but in the long-term is correlated with poorer performance. Left re-lateralization, if possible, seems to be the most effective in restoring language function. For a large subgroup of patients, aphasia therapy is not sufficient to resolve language deficits and not all patients are capable to endure intensive aphasia therapy. Therefore, non-invasive techniques (NIBS) such as transcranial direct current stimulation (tDCS) are currently explored as an add-on treatment to improve or accelerate therapy outcomes. tDCS is a painless and safe stimulation tool that modulates cortical excitability through weak polarizing currents (1 mA - 2 mA) between two electrodes. These weak currents are thought to induce a subthreshold shift of resting membrane potentials towards depolarization or hyperpolarization. The effects of stimulation depend on the polarity of the applied current relative to the axonal orientation. It has been found that tDCS not only triggers immediate aftereffects, but also long-lasting effects that persist beyond the stimulation time, even for up to 12 months. It was suggested that long-term potentiation (LTP) and long-term depression (LTD) might be responsible for these long-term effects, however the precise physiologic mechanisms of action are not yet fully understood.

• tDCS (Procedure): C-tDCS during the first 20 minutes of aphasia therapy, at an intensity of 1mA or sham-tDCS at an intensity of 0mA
• Aphasia therapy (Procedure): Based on linguistic tests, individualized aphasia therapy will be provided

Primary outcomes

• Change in naming performance assessed with the Boston Naming Test [baseline, 3 weeks, 3 +/-1 month]: Naming performance will be assessed with the Boston Naming Test at baseline, immediately following therapy, and after 3 +/- 1 month following treatment

Secondary outcomes

• Change in tolerability assessed with a Visual analogue scale [baseline, 2 hour (each session)]: A Visual analogue scale will asses tolerability before and immediately after each session
• Change in spontaneous speech assessed with a Semi-standardized interview of the AAT [baseline, 3 weeks, 3 +/- 1 month]: A Semi-standardized interview of the AAT will assess functional communication at baseline, immediately after therapy, and at 3 +/- 1 month follow-up
• Change in ERPs [baseline, 3 weeks, 3 +/- 1 month]: Evoked potentials will be measured at baseline, immediately after treatment and after 3 +/- 1 month
• Change in quality of life assessed with the SAQOL-39-NL [baseline, 3 weeks, 3+/- 1 month]: The SAQOL-39-NL will assess the quality of life at baseline, immediately after treatment and at 3 +/-1 month follow-up

Sex: All, ages: 18 Years to 85 Years

Inclusion Criteria:

* Diagnosed with mild to moderate aphasia (Token Test Score between 7 and 40) after a first left hemispheric ischemic or hemorrhagic stroke
* Inclusion > 6 months post-stroke
* Age 18 - 85 years
* Being right-handed (> +8 on the questionnaire for handedness, Van Strien)
* Mothertongue: Dutch
* Imaging (CT or MRI) prior to inclusion (in patient file), standard of care in the acute phase
* Signed Informed Consent (attachment 1)

Exclusion Criteria:

* History of other diseases of the central nervous system, psychological disorders and (developmental) speech and or language disorders
* Serious non-linguistic, cognitive disorders (as documented in the patients' medical history and inquired in the anamneses)
* Prior brain surgery
* Excessive use of alcohol or drugs
* New neurological symptoms between the acute stage and inclusion

• Veerle De Herdt, Prof. Dr., Principal investigator, University Ghent