Differentiating profiles of speech impairments in Friedreich's ataxia: a perceptual and instrumental approach

Background: The speech disorder associated with Friedreich's ataxia (FRDA) is classically described as ataxic dysarthria. However, variable neuropathology beyond the cerebellum, which may include the corticospinal and corticobulbar tracts, means that the dysarthria can be mixed rather than a pure ataxic dysarthria. Aims: To characterize physiological features of the dysarthria associated with FRDA and identify differential patterns of deviation that may occur across the subsystems of the speech-production mechanism in a series of seven case studies. Methods & Procedures: The assessment battery included a perceptual analysis of a speech sample using an interval rating scale, and a range of instrumental measures to investigate the respiratory, laryngeal, velopharyngeal and articulatory systems. Outcomes & Results: The results demonstrated the variability that exists in the dysarthria associated with FRDA, highlighting the existence of differential profiles of speech impairment. A particular distinction was observed between the presence of hypernasality and phonatory dysfunction, as evidenced by the instrumental results. Conclusions & Implications: The distinct profiles of dysarthria associated with FRDA indicate that approaches that address multiple subsystems are necessary for the accurate characterization and quantification of the motor speech disorder. Further research is required to investigate the decline in speech function as the disease progresses, as changes in speech function over time may be a good indicator of neurological decline in FRDA.