According to data released by WHO, cerebrovascular disease (aka stroke) is one of the chronic diseases with the highest incidence. The nature and degree of impacts on speech productions resulted from dysarthria due to stroke has attracted much interest and attention over several decades. The well-known dysarthric speech impairments are characterized by articulatory inaccuracy, speaking rate slowness, less prosodic variabilities, and reduced intelligibility. Several studies reported deviant kinematic features of tongue movement which comprise of longer duration, prolonged distance of movement, and reduced velocity, have been reported. Despite substantial research devoted to speech disorders associated with stroke, investigations using kinematic analysis of the tongue during speech are still scarce and limited. Kinematic analysis has been carried out mostly in populations with neurological disorders other than stroke (e.g., traumatic brain injury, amyotrophic lateral sclerosis, and Parkinson disease) and autoimmune diseases (i.e., multiple sclerosis). The lack of kinematic data relating to articulatory function poststroke highlights the urgent need for research using kinematic analysis to dissect and comprehend tongue functions associated with articulatory deficits of the stroke patients with dysarthria, in order to more clearly determine appropriate articulatory treatments for this population.
General speech profiles pertaining to stroke with a disorder (dysarthria) and
without a disorder (nondysarthria) can be vital information for assessment and intervention planning. Therefore, the primary aim of this thesis is to systematically examine the physiological and underlying pathological changes of the articulatory and rate dysfunctions in both speakers with dysarthria and without dysarthria post stroke utilizing quantitative physiological measures.
Ten individuals with dysarthria (Stroke+D) and nine speakers without dysarthria (Stroke−D) post stroke participated in this study. There were 14 males and five females with a mean age of 54.05 years (SD = 16.42), ranging from 28 to 81 years. The mean of time post stroke was 3.65 years (SD = 4.13 years), ranging from 0.4 to
The general speech perceptual features exhibited by the CVA speakers, as a group, was evaluated using five perceptual assessments and revealed significant impairments across parameters in the dimensions of articulation and speaking rate, compared to a control group of 19 non-neurologically impaired speakers who were matched for age and sex. Imprecise consonant production and overall slow speaking rate are major speech characteristics in most of the CVA speakers. Although the intelligibility factor was revealed to be significantly different between the CVA group and the control group, the effect of stroke on their overall intelligibility was not clearly evident, indicating possible influences on speech production from several other factors (i.e., compensatory strategies adopted).
Electromagnetic articulography (EMA), an objective and reliable kinematic device, has the ability to track the movements of the articulators by projecting electric signals among several receiver coils and three transmitter coils. Using this instrument, the profiles of speed and accuracy of the tongue movements based on the
reduced speaking-rate and the articulatory imprecision were manifest in both Stroke+D speakers and Stroke–D speakers. The results showed an overall decline in tongue-tip and tongue-back movements of the Stroke+D group at the habitual rate condition across most of the kinematic parameters, including velocity, acceleration, deceleration, distance, and duration of lingual movement, demonstrated. This finding confirmed that the Stroke+D speakers presented many kinematic-related speech difficulties during tongue movements in sentence production. The Stroke−D group, sharing similar kinematic performances with the controls, demonstrated only two deviant features: greater distance and longer duration of tongue movements during tongue-tip sentence production. The results are discussed in relation to associated physiological changes post stroke. Further underlying physiological evidence of the lingual kinematics is required to investigate such deviations in the stroke groups.
A successive analysis using the EMA assessment focused on the fast-rate production of the same sentence stimuli as those at the habitual rate condition. When comparing among the Stroke+D, Stroke−D, and controls, the results at the fast rate were consistent with those at the habitual rate across the majority of the kinematic variables, except for distance. At the fast rate condition, decreased speed-related parameters and increased duration of lingual movement were exhibited among the Stroke+D speakers. Unlike the results at the habitual rate, the Stroke−D speakers presented lower MV and MA values, leading to a prolonged duration of lingual movement. An increase in rate factor substantiates a tax effect upon the kinematic parameters of the tongue movement. During speech, subclinical impairments in lingual movement in only the Stroke−D group and a great variability in lingual
kinematic performances in all three groups were identified.
Group-based analyses confirmed the presence of articulatory-and-rate deviations in lingual kinematics in the Stroke+D speakers and subclinical motor impairment in the Stroke–D individuals, thereby, a longitudinal assessment was conducted to map out the patterns of recovery of the lingual kinematic function in patients with dysarthria post stroke (stroke year < 0.5 year). Six months after the initial assessments, a duplication of the perceptual battery, EMA assessment, and tongue pressure transducer assessment were carried out with three CVA participants who had mild to moderate dysarthrias (aged 35, 68, and 69 years). Each participant demonstrated different patterns of speech kinematics in tongue, in spite of sharing similar sites of stroke lesion and types of dysarthria. The outcome, therefore, indicated a considerable variance between the performances at 6 months and the performances at 12 months across the three cases. Comparisons of the lingual kinematics of the two-type sentence production between 6 months and 12 months as well as between habitual rate and fast rate were discussed. Three different patterns of speech-related motor recovery in tongue were determined in each stroke+D participant.
Finally, the kinematic of the EMA analysis in the three Stroke+D participants at 6 months and 12 months were compared to the control speakers (N = 15) matching the age and sex (male, mean age = 56.33 years, SD = 15.59). Again, varied kinematic outcomes were found at both 6 months and 12 months in each Stroke+D individual, when compared to the controls. One of the participants with dysarthria demonstrated comparable performances to the control speakers at both 6 months and 12 months post stroke; the other two participants exhibited impairments in a range of
kinematic variables. Particularly, at 12 months post stroke, one of the remaining participants was deemed to recover considerably to an extent of presenting lingual kinematics akin to the control speakers; whereas, the other showed an overall decline in the performance when comparing both 6-month performance and 12-month performance to the controls. The findings suggest distinct recovery patterns in lingual kinematics existing in the Stroke+D speakers. Possible factors related to the lingual kinematic impairments were extensively discussed and future investigations addressing the insufficiencies of the current thesis are recommended.