Evaluation of percent vocal creak and pitch strength as treatment response measures in adductor laryngeal dystonia

Adductor laryngeal dystonia (AdLD) causes involuntary laryngeal spasms, leading to voice disruptions. Quantifying these disruptions is critical for clinical care. Manual identification of disruptions is the gold standard, but is time-consuming and carries risk of human error, making it clinically impractical. Acoustic measures offer a scalable alternative, but can have limited sensitivity to change, potentially due to the prevalence of aperiodic phonation in AdLD. Recently, pitch strength (PS) and percent creak (PC) have emerged as promising alternatives. PS captures pitch salience even in aperiodic signals. PC quantifies the proportion of creaky phonation, capturing voice qualities characteristic of AdLD. We hypothesized PS would increase and PC would decrease with treatment. Fifteen AdLD patients were assessed before and 1 month after standard-of-care botulinum neurotoxin (BTX) treatment. PS and PC were measured during sustained /a/ and connected speech. Linear mixed effects models evaluated the effects of BTX and task. Despite a reduction in manually identified disruptions and improved patient-reported measures, PS and PC did not change significantly. Findings suggest PS and PC are less sensitive than manual identification of voice disruptions for assessing BTX effects in AdLD. There is a need for objective metrics that capture the diverse acoustic consequences of spasms in AdLD.