Botulinum Toxin Treatment for Adductor Laryngeal Dystonia Reduces Speech-Related Cognitive Load.

[OBJECTIVES] Botulinum toxin (BTX) treatment has previously been shown to improve voice quality, quality of life, and the physical component of vocal effort in adductor laryngeal dystonia (ADLD) patients. More recently, cognitive load has been identified as a contributor to vocal effort in ADLD patients. This study aims to identify the effects of BTX on speech-related cognitive load and the association of cognitive load with voice-related quality of life.

[METHODS] A prospective study of ADLD patients undergoing BTX treatment was conducted. NASA Task Load Index (NASA-TLX), the Voice-Related Quality of Life (VRQOL) scale, and voice recordings were obtained on the day of, 1 week after, and 4-6 weeks after BTX injection. Auditory-perceptual evaluation of the voice samples was performed by four speech-language pathologists.

[RESULTS] Twenty-one patients completed all measures and voice recordings. Mental and physical demand subscales, derived from the NASA-TLX, decreased by 4-6 weeks (p = 0.001 and 0.019, respectively). Median VRQOL improved from 40 to 68 by 4-6 weeks post injection (p < 0.001). On multilevel multiple linear regression, mental demand and overall voice quality correlated with VRQOL (p = 0.003 and 0.001, respectively), but physical demand did not (p = 0.16).

[CONCLUSIONS] Laryngeal BTX injection reduces cognitive load associated with speaking in ADLD patients. Cognitive load may be more predictive of voice-related quality of life than the physical effort associated with speaking.