For adductor spasmodic dysphonia, there is a need for establishing a new therapy under the present circumstance where no standard therapy has been established yet and existing therapies fail to provide permanent effect. Evaluation of the efficacy of type 2 thyroplasty using titanium bridges will expand the therapeutic options available for adductor spasmodic dysphonia and establishment of a standard therapy.

Spasmodic dysphonia is a type of functional dysphonia not associated with any organic abnormality or palsy of the larynx. The speech disorder in this disease is caused by involuntary and intermittent spasms of the intralaryngeal muscles (Castelon, 2002).

There is no curative treatment for this disease. Conservative therapies include voice training (voice therapy) and muscle relaxant medication to ease the tension in the larynx during speech, although there is not much evidence to support the effectiveness of either. An internationally employed therapy is local injection of botulinum toxin A into the intralaryngeal muscles to suppress involuntary movements of the vocal cords. The injection can be administered percutaneously from the anterior neck within a short time, and a number of reports have indicated a greater than 90% efficacy of this treatment (Tisch 2003, Blitzer 2010). However, this local injection therapy is effective only for a limited period of 3 to 4 months, and periodic injections have to be continued throughout life for maintaining relief from the symptoms under the present circumstances.

Type 2 thyroplasty is an operative procedure in which the thyroid cartilage is incised at the midline, and the incised gap is opened and fixed with the thyroarytenoid muscles attached on both sides, so that the vocal cords do not shut too tightly during speech even with strong adduction of the glottis, as the symptoms of adductor spasmodic dysphonia are caused by excessive closure of the glottis due to strong involuntary and intermittent adduction of the intralaryngeal muscles (Isshiki 2001).

In 2002, the titanium bridge made of biocompatible pure titanium was developed in Japan for exclusive use in type 2 thyroplasty (Isshiki 2004). When the titanium bridge was used in actual cases, the symptoms disappeared without recurrence after the operation (Sanuki 2007, Sanuki 2009, Isshiki & Sanuki 2009, Sanuki 2010).

There is a need for establishing a new therapy under the present circumstance where no standard therapy has been established yet and existing therapies fail to provide permanent effect. Evaluation of the efficacy of type 2 thyroplasty using titanium bridges will expand the therapeutic options available for adductor spasmodic dysphonia and establishment of a standard therapy.

Inclusion Criteria:

1. Diagnosis of adductor spasmodic dysphonia by a board certified otorhinolaryngologist certified by the Oto-Rhino-Laryngological Society of Japan, Inc.
2. At least 1 year experience of subjective or objective labored speech production, or pauses on certain sounds, due to adductor spasmodic dysphonia
3. A total score of 20 or more on the Voice Handicap Index-10 (VHI-10)
4. Non-responders to voice therapy performed before informed consent
5. 18 through 80 years of age inclusive at the time of informed consent
6. Written informed consent to participate in this study, provided by patients or their legally acceptable representatives

Exclusion Criteria:

1. Dysphagia, laryngeal paralysis, or any structural disorder in the vocal cord
2. Previous surgery for adductor spasmodic dysphonia
3. Local injection of botulinum toxin type A into the intralaryngeal muscles within 6 months before informed consent
4. Serious concomitant diseases
5. Surgery with general anesthesia scheduled during the study period or surgery performed within the past 4 weeks
6. Participation in any other study using any other intervention within 12 weeks before informed consent, or planned participation in such a study during the study period after enrollment in this study
7. Psychiatric disorder requiring treatment, or mental or intellectual disability that may affect the conduct of the study
8. A history of alcoholism or drug abuse
9. A history of hypersensitivity to pure titanium
10. Women who are pregnant or planning to become pregnant during the study period
11. Patients deemed ineligible for this study by the investigator for any other reason