Rapid voice tremor, or "flutter," in amyotrophic lateral sclerosis

Area of Science:

• Neurology
• Speech-Language Pathology
• Biomedical Engineering

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons.
• Voice tremor, or "flutter," is a notable symptom in some ALS patients, impacting speech.
• The precise acoustic characteristics and origin of this voice tremor in ALS remain unclear.

Purpose of the Study:

• To investigate the frequency characteristics and origin of rapid voice tremor in patients with ALS.
• To compare voice modulation patterns between ALS patients with tremor and healthy controls.

Main Methods:

• Acoustic analysis of sustained /a/ vowel phonation from eight ALS patients and eight age/sex-matched controls.
• Demodulation of phonation into amplitude and frequency components.
• Fast Fourier Transform (FFT) analysis on 1-second segments to identify tremor characteristics.

Main Results:

• Patients with ALS displayed multiple combinations of amplitude and frequency modulations compared to controls.
• Control subjects exhibited consistently low levels of amplitude and frequency modulations.
• While not clearly localized to a single spectral point, modulations were significantly more prominent in ALS patients.

Conclusions:

• ALS patients exhibit significantly higher amplitude and frequency modulations during phonation compared to healthy individuals.
• The observed voice tremor characteristics in ALS are more pronounced than in normal subjects.
• The origin of these aberrant modulations in ALS is speculative, possibly stemming from peripheral rather than central nervous system dysfunction.