Non-invasive Brain Stimulation as a Treatment for Dysarthria Post-stroke

A Randomized Controlled Trial Study of the Use of Transcranial Direct Current Stimulation (tDCS) in Treating Dysarthria Post-stroke

A total of 9 Cantonese-speaking chronic post-stroke patients who are suffering from dysarthria was recruited and randomly divided into treatment group and sham group. For the treatment group, an anodal high-definition tDCS of 2 milliampere (mA) lasting for 15 minutes was delivered to the primary motor cortex (SM1) in 10 daily sessions during a 2-week period. For the sham tDCS group, the same setting of tDCS electrodes was applied on the scalp, but the stimulation only lasted for 30 sec in order to cause similar sensation on the scalp as the other group. Simultaneous to the tDCS stimulation, both groups will receive speech and voice therapy for 30 minutes. An array of outcome measures reflecting speech production ability including acoustic, kinematic, perceptual and self-perceptual qualities was obtained before and after stimulation. It was anticipated that post-stroke dysarthric patients will see improvement in speech production after stimulation. The results provided important insights into the effects of tDCS on articulatory movement in individuals with dysarthria post-stroke.

Group 1 (n = 5) received anodal tDCS stimulation and intensive speech and voice therapy; tDCS and speech therapy was applied in 10 daily sessions during a 2-week period, administered on Monday to Friday. The anodal stimulation was delivered to the primary motor cortex (SM1) of the orofacial area.

Group 2 (n = 4) received sham tDCS stimulation and intensive speech and voice therapy. For the sham tDCS group, the same setting of tDCS electrodes was applied on the scalp, but the stimulation only lasted for 30 sec in order to cause a similar sensation on the scalp. tDCS and speech therapy was applied in 10 daily sessions during a 2-week period, administered on Monday to Friday.

2mA of tDCS was delivered to the orofacial area of the primary motor cortex (SM1) for 15 minutes. Speech therapy was delivered simultaneously.

2mA of tDCS was delivered to the orofacial area of the primary motor cortex (SM1) for 30 sec. Speech therapy was delivered simultaneously.

All participants were required to produce a sustained vowel /a/, repeated some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/), produce some single words, read a standard paragraph in Cantonese and had a two-minute conversation with the investigator. A professional grade microphone (SM58, Shure, USA) was used to record the speech production. Experienced speech-language pathologists blinded to the neurological condition and history of each participant analyzed the speech samples independently using a perceptual rating scale including 21 speech dimensions covering eight categories, including pitch, loudness, voice quality, resonance, rate, articulation, tone, and general impression. The speech samples were rated using a seven-point equal-appearing interval scale, with a "1" indicating within typical limit performance and a "7" severely deviated from the normal.

The lip and tongue function during speech production were traced real time and objectively measured using an electromagnetic articulography. All participants were required to produce single-syllable real words of consonant-vowel (CV) construction at high level tone embedded in a carrier phrase and repeat some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/). A custom-written analysis programme was used to annotate and calculate the kinematic measures, including duration (ms), distance (mm), maximum velocity (mm/s), maximum acceleration (m/s2) and maximum deceleration (m/s2) in the approach (movement towards the upper lip/palate) and release (movement away from the upper lip/palate) phases along the z-axis, i.e., along the mid-sagittal plane.

The lip and tongue function during speech production were traced real time and objectively measured using an electromagnetic articulography. All participants were required to produce single-syllable real words of consonant-vowel (CV) construction at high level tone embedded in a carrier phrase and repeat some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/). A custom-written analysis programme was used to annotate and calculate the kinematic measures, including duration (ms), distance (mm), maximum velocity (mm/s), maximum acceleration (m/s2) and maximum deceleration (m/s2) in the approach (movement towards the upper lip/palate) and release (movement away from the upper lip/palate) phases along the z-axis, i.e., along the mid-sagittal plane.

The lip and tongue function during speech production were traced real time and objectively measured using an electromagnetic articulography. All participants were required to produce single-syllable real words of consonant-vowel (CV) construction at high level tone embedded in a carrier phrase and repeat some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/). A custom-written analysis programme was used to annotate and calculate the kinematic measures, including duration (ms), distance (mm), maximum velocity (mm/s), maximum acceleration (m/s2) and maximum deceleration (m/s2) in the approach (movement towards the upper lip/palate) and release (movement away from the upper lip/palate) phases along the z-axis, i.e., along the mid-sagittal plane.

The lip and tongue function during speech production were traced real time and objectively measured using an electromagnetic articulography. All participants were required to produce single-syllable real words of consonant-vowel (CV) construction at high level tone embedded in a carrier phrase and repeat some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/). A custom-written analysis programme was used to annotate and calculate the kinematic measures, including duration (ms), distance (mm), maximum velocity (mm/s), maximum acceleration (m/s2) and maximum deceleration (m/s2) in the approach (movement towards the upper lip/palate) and release (movement away from the upper lip/palate) phases along the z-axis, i.e., along the mid-sagittal plane.

The lip and tongue function during speech production were traced real time and objectively measured using an electromagnetic articulography. All participants were required to produce single-syllable real words of consonant-vowel (CV) construction at high level tone embedded in a carrier phrase and repeat some syllables (i.e., /pa/, /ta/, /ka/ and /pataka/). A custom-written analysis programme was used to annotate and calculate the kinematic measures, including duration (ms), distance (mm), maximum velocity (mm/s), maximum acceleration (m/s2) and maximum deceleration (m/s2) in the approach (movement towards the upper lip/palate) and release (movement away from the upper lip/palate) phases along the z-axis, i.e., along the mid-sagittal plane.

Inclusion Criteria: Cantonese-speaking adults At least 6 months after their initial stroke Dysarthria post-stroke Exclusion Criteria: A personal or family history of epilepsy or seizures A history of another neurological condition Speech disorders Voice disorders Oro-maxillo-facial surgery involving the tongue and/or lip Severe cognitive impairment Severe aphasia Heart disease Metallic foreign body implant On medications that lower neural thresholds (e.g. tricyclines, antidepressants, neuroleptic agents, etc.)