Supplemental Material for: Recovery of Dysarthria in Anti-GluK2 Antibody–Associated Autoimmune Cerebellar Ataxia: A Longitudinal Acoustic and Perceptual Case Report

Speech tasks included alternating motion rate (AMR), sequential motion rate (SMR), and oral reading. Acoustic analyses included syllable duration and repetition rate from AMR and SMR tasks, peak syllable intensity from AMR, and voice onset time (VOT) and pause-related measures from oral reading, together with coefficients of variation (CVs). Speech intelligibility was assessed using a visual analog scale (VAS).

A phrasing-based strategy was additionally implemented during routine speech-language therapy, and its potential influence on speech rhythm was explored. Speech intelligibility improved over time (VAS: 36→66→91→94), while AMR repetition rate increased (/pa/: 3.54→3.77→4.38→5.43 mora/s). Progressively lower CVs of syllable duration were observed during AMR tasks, indicating enhanced temporal regularity, whereas SMR showed more heterogeneous changes.

VOT shortened across assessment sessions, consistent with improved articulatory timing. Following introduction of the phrasing-based strategy, pause frequency increased transiently (19→27→40→19) before returning to the baseline level, accompanied by changes in pause-duration variability. </p><p dir="ltr">Conclusion</p><p dir="ltr">Speech changes appeared to reflect non-uniform improvements in speech timing and articulatory coordination during the course of immunotherapy.

These findings support the view that speech timing may improve gradually rather than uniformly across subsystems in ACA. Longitudinal speech assessment may serve as a useful behavioral indicator of recovery, and phrasing-based rate control may support rhythm stabilization in patients with residual dyscoordination in clinical settings.</p>