Acoustic Analysis of Voice in Individuals with Amyotrophic Lateral Sclerosis

Park, Jeong Hyeog; Nam, Soon Yuhl

Abstract

BACKGROUND AND OBJECTIVES: Amyotropic lateral sclerosis (ALS) is a progressive neuromuscular disease that involves degeneration of upper motor neurons in the cortex and lower motor neurons in the brain stem and spinal cord. Although there is a decline in the articulatory dysfunction, respiratory, and phonatory dysfunctions are known to occur in ALS. However, the pattern of disease progression and early identification of phonatory changes are not well documented. The purpose of this study was to compare selected acoustic parameters of voice in the normal control group to the ALS group who were perceptually free of vocal symptoms. Significant differences between the two groups could indicate that signs of bulbar degeneration in ALS may be present even when the voice is clinically perceived as normal.
MATERIALS AND METHODS
The authors used a computerized acoustic analysis program (CSL-MDVP) to measure mean fundamental frequency (Fo), jitter, shimmer, and noise to harmonics ratio (NHR) from voice samples of ALS patients and compared this results with the acoustic parameters of 60 control subjects (men: 30, women: 30) who have no history of neurologic disease and were over 60 years old.
RESULTS
There were significant group differences for jitter, shimmer, and NHR in male ALS. There was significant group difference for jitter in female ALS.
CONCLUSION
Certain acoustic measures of voice may be sensitive indicators of early laryngeal deterioration in ALS. Acoustic analysis of voice may be one way of detecting aberrant vocal features before the human ear detects dysphonia, and jitter may be the most sensitive acoustic variable.