Quantitative voice analysis in the assessment of bulbar involvement in amyotrophic lateral sclerosis

Bulbar and pseudobulbar symptoms are diagnostic criteria of amyotrophic lateral sclerosis (ALS). One of the earliest symptoms of bulbar involvement is voice deterioration. Until now voice assessment in ALS patients has been done mainly by perceptual analysis. The objective parameters, including acoustic measures, one aerodynamic measure and the maximal phonation time, have been measured only in a few small series of patients. The first purpose of this prospective study was to determine which vocal parameters discriminate ALS patients with bulbar involvement from control patients. The second was to identify sensitive parameters for early detection of voice deterioration due to bulbar involvement in pre-symptomatic ALS patients. The voices of 63 female ALS patients, including 40 with bulbar symptoms (sALS patients) and 23 without bulbar symptoms (aALS patients), were studied using an objective voice analysis system that allows simultaneous analysis of acoustic and aerodynamic parameters. Measurements were compared with those obtained in 40 normal female subjects (control patients). Five of eight acoustic parameters were significantly different among the three groups: jitter, coefficient of variation for frequency, shimmer, number of harmonics, and maximum phonatory frequency range. Three aerodynamic parameters, phonatory airflow, cycle-to-cycle variation for phonatory airflow, and coefficient of variation for phonatory airflow were significantly different between sALS patients and control patients. No aerodynamic parameter allowed discrimination between aALS patients and control patients. This study shows that acoustic parameters are more sensitive than aerodynamic parameters for early detection of bulbar involvement. Nevertheless, the measurements used can predict bulbar involvement in 73% of those in the sALS group, but only in 52% of those in the aALS group.