Comparison of Voice Aerodynamics Characteristics in Spasmodic Dysphonia and Muscle Tension Dysphonia

Abstract

Purpose: Phonation or the generation of audible sound energy is caused by muscular and aerodynamic activities that affect the vocal cords. The main objective of this study was to determine aerodynamic parameters in three categories of normal, spasmodic dysphonia and muscle tension dysphonia. Methods: Study population consisted of 30 individuals (ten subjects with spasmodic dysphonia, ten subjects with muscle tension dysphonia and ten normal subjects). Vital capacity of each individual was recorded by a spirometer and maximum phonation time was calculated with the help of stop watch. The data were analyzed with Spss 19 statistical software. Results: The maximum phonation time in muscle tension dysphonia was lower than two other groups and in spasmodic dysphonia group was lower than normal, the mean difference between groups was significant (p<0.001). Vital capacity in the group of muscle tension dysphonia was lower than other groups and in spasmodic dysphonia was equal to the normal group, mean difference between groups was statistically significant (p<0.001). Phonation quotient in muscle tension dysphonia was more than spasmodic dysphonia group and in spasmodic dysphonia group was higher than normal and again the mean difference between groups was statistically significant (p<0.001). Conclusion: Maximum phonation time between three categories of normal, spasmodic dysphonia and muscle tension dysphonia was significantly different. Vital capacity in normal and spasmodic dysphonia group did not differ significantly and in muscle tension dysphonia group was different compared to other two groups. It seems that vital capacity reduction in this category of patients is an explanation for the occurrence of this type of dysphonia. The results showed that changes in the aerodynamic parameters in addition to separate the normal group from voice disorders, depending on the type of disorder as well. These differences must be considered in the process of assessment and therapeutic interventions.