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

Abstract

Introduction Temporal coordination of speech segments is thought to involve cerebellar contributions to the coordination and timing of articulatory movements. Although cerebellar dysfunction leads to dysarthria, speech symptoms in inflammatory cerebellar disorders may improve following immunotherapy. However, longitudinal changes in speech characteristics during recovery remain insufficiently described. Previous studies have reported abnormalities in syllable timing, speech rate, and articulatory coordination in cerebellar dysarthria, but longitudinal changes in these acoustic features during recovery remain poorly understood. This study aimed to describe longitudinal speech changes in a patient with anti-glutamate kainate receptor subunit 2 (GluK2) antibody-associated autoimmune cerebellar ataxia (ACA) using acoustic and perceptual analyses. Case Presentation A 50-year-old woman with anti-GluK2 antibody-associated ACA was evaluated at four time points during hospitalization (days 9-11, 15, 22-25, and 41 after symptom onset). 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. Conclusion 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.