Analysis of Articulatory Dynamics in Dysarthria Following Brain Injury in Childhood Using Electromagnetic Articulography and Electropalatography

Article excerpt

Two physiological assessments, electromagnetic articulography (EMA) and electropalatography (EPG), were used simultaneously to investigate the articulatory dynamics in an 18-year-old male with dysarthria 9 years following traumatic brain injury (TBI). Eight words consisting of [TEXT NOT REPRODUCIBLE IN ASCII] in word initial and word final positions were produced up to 10 times. A nonneurologically impaired male served as a control subject. Six parameters were analyzed using EMA: velocity, acceleration, deceleration, distance, duration, and motion path of tongue movements. Using EPG, the pattern and amount of tongue-to-palate contact and the duration of the closure/constriction phase of each consonant produced were assessed. Timing disturbances in the TBI speaker's speech were highlighted in perceptual assessments in the form of prolonged phonemes and a reduced speech rate. EMA analysis revealed that the approach and release phase durations of the consonant productions were within normal limits. Kinematic strategies such as decreased velocity and decreased distances traveled by the tongue, however, may have counterbalanced each other to produce these appropriate results. EPG examination revealed significantly longer closure/constriction phase periods, which may have contributed to the prolonged phonemes and reduced speech rate observed. The implications of these findings for the development of treatment programs for dysarthria subsequent to TBI will be highlighted.

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Traumatic brain injury (TBI) is a leading cause of death and disability in the Western world (Sosin, Sniezek, & Thurman, 1996). Studies have indicated the incidence of TBI in children to be approximately 200 per 100,000 per year (Annegers, 1983; Cahill, Murdoch, & Theodoros, 2001). A range of disabilities can be seen in this population, particularly in those who have suffered from severe brain injuries. In a study carried out by Emanuelson, von Wendt, Lundalv, and Larsson (1996), it was found that almost all of the 25 children with severe TBI under investigation were left with some major impairments. Dysarthria is a commonly reported consequence of severe TBI in children (Costeff, Groswasser, & Goldstein, 1990). The term dysarthria refers to a group of neuromotor speech disorders caused by disturbances in the muscular control of the speech production mechanism as a result of lesions sustained within the central and/or peripheral nervous systems (Darley, Aronson, & Brown, 1975). A dysarthric speech disturbance not only can have significant negative effects on a child's ability to reintegrate into society and educational settings, but its effects often carry into adulthood. Little research, however, has been carried out on the long-term outcome of this disorder. The available reports are typically brief and rely on perceptual assessments or by self-report (e.g., Costeff, Groswasser, Landman, & Brenner, 1985; Costeff et al., 1990; Emanuelson et al., 1996). As knowledge of the mechanisms underlying a specific disorder is crucial for its treatment, advanced understanding of dysarthria following childhood TBI is required if more effective diagnostic and therapeutic techniques are to be developed (Theodoros, Shrapnel, & Murdoch, 1998).

In the past, perceptual analysis has been the preferred means of assessing dysarthric speech. Perceptual analysis has continued to be an important tool for speech assessment. However, the limitations of this approach are recognized and an extensive range of instrumentation has been developed to examine the underlying pathophysiology of the speech production mechanism. As stated by Hirose (1986), physiological analysis is a valuable complement to perceptual analysis for a number of reasons. Dysarthric speech is the end product of the motor characteristics of the articulators. Therefore, an examination of the motor patterns of the articulators appears to be a more direct and objective approach to assessing the nature and severity of dysarthric speech. …