However, the importance of differentiating them is critical in terms of the implications of the underlying neurologic origin, disease process and progression, and treatment options. The vocal symptoms of individuals with ADSD, Tremor, and ALS may sound similar. Comparison with available normative data indicated a slight increase in Fo for males in the ALS group and a slight decrease in Fo for females in the Tremor Group. Voice and Tremor Analysis was separated by gender and is summarized in Table 2. In addition, The SD and Tremor groups had disproportionately more females than males versus the ALS group. Overall, the SD group was younger than the other two groups. The composition of the three groups of patients is summarized in Table 1. The specifics of patient selection will be addressed below.
Tremulous vocal quality was studied in individuals with essential voice tremor. For spastic vocal quality, individuals with a spastic dysarthria as part of the bulbar form of ALS were included. Spasmodic quality was studied in individuals with ADSD.
Three study groups were chosen to compare the acoustic characteristics of spastic, spasmodic, and tremulous vocal quality.
The purpose of this investigation was to determine if spastic, spasmodic, and tremulous vocal qualities of neurologic origin could be differentiated on the basis of acoustic and motor speech parameter analysis. A system of combined acoustic analysis along with assessment of other features of motor speech production, including diadochokinesis, speaking rate, and intonation features, might provide additional information to differentiate these three similar but different neurologically based voice disorders. It was hypothesized that acoustic analysis alone would not be sufficient to differentiate the spasmodic vocal quality of an individual with ADSD from the tremulous voice of one with Tremor or that of a spastic dysarthria in one with ALS. 10 In contrast, essential voice tremor, which is characterized by regular and rhythmic tremulous vocal quality may or may not be limited to the intrinsic laryngeal musculature alone or may also involve the palate, hypoglossus, strap muscles, rectus abdominus, and diaphragm.12., 13., 14.Īlthough these three disorders have different underlying neurologic origins, they share similar perceptual features of strained, strangled, and tremulous vocal quality. 5 The spastic quality more frequently found as part of a central neurologic dysarthria of lower motor neuron, pseudobulbar origin-like amyotrophic lateral sclerosis (ALS), more typically involves the entire phonatory system. The spasmodic vocal quality that is typically seen in the adductor variety of spasmodic dysphonia (ADSD) reflects a focal dystonia and is characterized by irregularly strained and strangled phonation. However, these variables have not been successful in differentiating spasmodic dysphonia from other neurologic diseases.2., 11. voice tremor, 8 and spastic dysarthria associated with amyotrophic lateral sclerosis.9., 10. Traditional acoustic analyses including fundamental frequency, jitter, shimmer, and noise-to-harmonic ratio analyses have differentiated normal subjects from those with spasmodic dysphonia,4., 5., 7. 4 For example, the characteristic strained and strangled voice of the individual with adductor spasmodic dysphonia may also be found in other neurologic disorders, including Parkinsonism, cerebellar ataxia, Huntington's disease, and essential tremor.5., 6. Furthermore, they may present as part of an underlying neurologic disorder or as a result of vocal misuse, as may be seen in some cases of muscular tension dysphonia. Spastic, spasmodic, and tremulous vocal qualities may occur in isolation or present as part of a more central speech disturbance. 2 However, these vocal qualities have been difficult to analyze through traditional acoustic measures because of their inconsistent and variable presentation that may further vary as individuals develop changing compensatory strategies to vocalize. The ability to objectively characterize vocal qualities like spastic, spasmodic, and tremulous may aid in differentiating one from the other, aid in quantifying the severity level, and provide a basis for monitoring the effects of treatments. 1 These characteristics may be found in neurologically and functionally based voice disorders. Strained, strangled, and tremulous vocal qualities may frequently sound similar and be difficult to differentiate.
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