Spasmodic dysphonia: a natural history and patient demographics
Moses, Andrew A
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Dystonia is a hyperkinetic movement disorder that can affect a variety of people at different ages. The characteristics are involuntary repetitive contractions of muscles, causing stereotyped movement and postures, or torsion. These movements are caused by the co-contraction of both agonist and antagonist muscles. Spasmodic dysphonia, or SD is a type of dystonia that is characterized by involuntary contraction of the muscles involved in phonation and typically begins in those who are over the age of 28. The morphology of the laryngeal nerves and intrinsic laryngeal muscles are normal in most patients, and this suggests that the cause of the misfiring is upstream to the larynx. Spasmodic dysphonia is separated into two categories, adductor or abductor type spasmodic dysphonia or ADSD and ABSD, respectively. In this study we evaluated a population of 74 SD patients over several years, compiling data on demographics, onabotulinumtoxinA treatment, the difference between age of onset and age at diagnosis, and Voice-Related Quality of Life Survey (V-RQOL) results. Our results indicated that the vast majority, 70 patients, had ADSD while 4 had ABSD. The average age of onset was 43.1 years old, and the average age at diagnosis was 50.2, making the average difference between age of onset and age at diagnosis 7.1 years. The time between symptom onset and diagnosis varied considerably when patients were subdivided into those with symptom onset before or during 1983 and those with symptom onset after 1983. The year after 1983, 1984, was chosen, as this is the point at which botulinum toxin treatment for SD became available. The elapsed time between symptom onset and diagnosis varied for patients that had symptoms onset prior to 1983 and after 1983, 27.7 years and 3.4 years respectively. The total V-RQOL score for the before treatment group was 33, and the total score for the after treatment with onabotulinumtoxinA group was 15, making the total drop in points 18 or a 54.5% decline in severity of voice symptoms. The analysis of the botulinum toxin treatment over time for SD patients showed that there was an increase of 0.3 onabotulinumtoxinA units per true vocal fold for ADSD patients and 95.6 onabotulinumtoxinA units per posterior cricoarytenoid muscle for ABSD patients. The Burke-Fahn-Marsden Dystonia Rating Scale was effective to evaluate whether spasmodic dysphonia symptoms worsened over time with or without botulinum toxin treatment, and overall our results indicate symptoms do not worsen over time, although they also do not get better over time as well. This shows that while botulinum toxin is a successful treatment of SD patient symptoms, it does not treat the cause of spasmodic dysphonia and is therefore not a permanent solution. The V-RQOL over time showed a drop in score before treatment as opposed to after treatment. A student's t-test was performed at a 95% confidence interval, and these changes were shown to be statistically significant when compared to no change in V-RQOL scores (p=0.027). This shows that while botulinum toxin is not a permanent cure, it is an effective treatment and the best available treatment at this time.
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