Processes in Post-Traumatic Dysarthria: A Longitudinal Case Study

Abstract Post-traumatic dysarthria is a motor speech disorder secondary to paresis or paralysis of the articulatory musculature induced by head trauma. It is a complex disorder which occurs as a result of traumatic brain injury (TBI) and a subsequent coma. The present study investigates the characteristics of the speech of a 23-year-old Polish male subject with TBI, 12 months post-trauma, who was comatose for three weeks. The subject was diagnosed with moderate post-traumatic dysarthria and moderate posttraumatic aphasia. For the purpose of our research, the subject's speech was examined three times in the course of four months. During this period, he was undergoing a holistic rehabilitation program, including speech therapy. A detailed acoustic analysis of the subject's speech was carried out to obtain an accurate database for the investigation of the phonetic and phonological processes occurring in his post-coma speech. The processes were analyzed within the frameworks of the theories of Natural Phonology and Phonology as Human Behavior. The results indicate that, considalthough the dysarthric processes reflect the processes found in first language acquisition, they are both more idiosyncratic and easier to predict. The subject exhibited difficulties with maximum aperture and maximum closure of the vocal tract, most likely due to limited movements of the articulators. Hence, the centralization of vowels and spirantization of consonants were very common processes. Acoustic analysis enabled the discovery of a few processes, not previously reported in the literature. Two of them are: (1) Incomplete Consonant Closure—the articulators approach but do not reach the target, but the consonant intended can still be discriminated, and (2) Consonant Approximation—an incomplete approximation of the articulators appearing in positions where a consonant is expected, visible only on a spectrogram. During the period of four months, the subject's speech notably improved through the use of more communicative processes (i.e., there were more substitutions than omissions). At the same time, however, the number of processes used by the subject was not indicative of the intelligibility of his speech because the total number of processes which occurred in the first study decreased only by 13.7% in the third study. Additionally, positive changes in other aspects of speech, such as phonation, voice strength, fluency and intonation were also observed.