short arm of chromosome 19 (19p13.2-p13.3). This gene encodes a tubulin gene. The pathophysiology of this condition has yet to be determined. Treatment There are a number of potential treatments for spasmodic dysphonia, including Botox, voice therapy, and surgery. A number of medications have also been tried including anticholinergics (such as benztropine) which have been found to be effective in 40-50% of people, but which are associated with a number of side effects. Botulinum toxin Botulinum toxin (Botox) is often used to improve some symptoms of spasmodic dysphonia through weakening or paralyzing the vocal folds, thus preventing muscle spasms. The level of evidence for its use is currently limited; little is known about optimal dosage, frequency of injections, or exact location of injection. However, it remains a choice for many people due to the predictability and low chance of long term side effects. It results in periods of some improvement, with the duration of benefit lasting for 10–12 weeks on average before symptoms return to baseline. Repeat injection is required to sustain good vocal production, as results are only temporary. Some transient side effects observed in adductor spasmodic dysphonia include reduced speaking volume, difficulty swallowing, and a breathy and hoarse voice quality. While treatment outcomes are generally positive, it is presently unclear whether this treatment approach is more or less effective than others. Voice therapy Voice therapy appears to be ineffective in cases of true spasmodic dysphonia. However, as it is difficult to distinguish between spasmodic dysphonia and functional dysphonias, and misdiagnosis is relatively common, trial of voice therapy is often recommended before more invasive procedures are tried. Some also state that it is useful for mild symptoms and as an add-on to botox therapy and others report success in more severe cases. Laryngeal manual therapy, which is massaging of the neck and cervical structures, also shows positive results for intervention of functional dysphonia. Surgery If other measures are not effective, surgery may be considered; however, evidence to support surgery as a treatment for SD is limited. Treatment outcomes are generally positive, though more research is required to determine its effectiveness. Post-surgery voices can be imperfect and about 15% of people have significant difficulties. If symptoms do recur, this typically happens in the first 12 months. As of 2011, surgery was rarely used as a treatment approach for SD. Surgical approaches include recurrent laryngeal nerve resection, selective laryngeal adductor denervation-reinnervation