Higher-Faster-Farther: Maximum Performance Tests in the Assessment of Neurogenic Speech Impairment

Background: Maximum performance tests are widely used in dysarthria assessment. From a theoretical perspective, the motor demands of such tasks differ from those of speaking. Therefore, their validity as measures of dysarthric impairment needs to be established empirically. Patients and Methods: Maximum phonation time (MPT) and maximum syllable repetition rate (MRR) were compared with sentence reading/repetition tasks. In study 1, 130 patients with neurologic movement disorders and 130 healthy control participants were examined. Presence/severity of dysarthria was measured using psychometrically standardized auditory scales. In study 2, 16 healthy volunteers participated in an experiment designed to examine the intraspeaker variability of MPT, MRR, and sentence repetition across eight trials. Results: Study 1: MPT made no reasonable contribution to the diagnosis of dysarthria or of any specific dimension of perceived speech impairment. MRR correlated with overall speech impairment but turned out to be an insensitive and highly unspecific statistical marker, afflicted with aetiology-specific errors. Study 2: compared with sentence repetition, both MPT and MRR demonstrated highly increased within-subject inconsistencies. Conclusion: The validity of MPT and MRR tasks as measures of dysarthria is still unsettled.