Botulinum toxin (BTX) injection to the thyroarytenoid muscle has been a standard therapy for adductor spasmodic dysphonia (ADSD) worldwide, but treatment has been different here in Japan. Clinical use of BTX for strabismus was started in the early 1980s and application for spasmodic dysphonia (SD) patients followed after that. There were so many reports which showed the positive results of BTX injection to ADSD patients that this soon became a standard therapy in the US. In Japan, application of BTX for clinical use was started for blepharospasm from 1996 but it wasn’t until 2018 that the BTX injection for SD patients was approved by the Japanese Ministry of Health, Labour and Welfare. Voice specialists in Japan had been struggling with treatment for SD patients since they couldn’t use BTX for many years. They felt powerless whenever they saw SD patients and were desperate to create a new treatment approach.
In 2000, Isshiki’s group invented a surgical approach for ADSD patients named Type 2 Tyroplasty. The mechanism of ADSD is still not fully understood, however, it is a common knowledge that the strangulated voice is caused by a tight closure of the glottal gap which blocks the airflow from the lungs. The concept of this surgery aims to smooth the airflow by making the glottal gap wider during phonation.
The surgical procedure is as follows: Following local anesthesia using xylocaine, a 4cm (1.5 inch) incision is made at the front of neck to expose the laryngeal cartilage. Thyroid cartilage is carefully separated at the midline to avoid perforating the larynx lumen. By spreading both sides of the thyroid cartilage, the anterior glottal gap becomes wider, the airflow through the vocal folds becomes smooth and the voice strangulation is relieved. The gap between both sides of the thyroid cartilage can be adjusted, so patients are asked to speak during the procedure to find the most appropriate gap which makes patients feel there is least strangulation. After determining this gap, the corresponding sized titanium bridge (2.0-5.0 mm), which were specially made for this surgery, are set in place and fixed by nylon suture at the superior and inferior part of the gap between both sides of the thyroid cartilages. Surgery is finished by closing the skin incision. The procedure take between one to two hours. Patients are allowed to speak three days after the surgery, and can talk loudly one month afterwards. A possible complication which could be serious is postoperative hemorrhage resulting in airway obstruction; however, this has never been experienced.
This easy, quick and adjustable procedure has been developed in Japan and is a standard therapy as well as BTX injection at the present time. A remarkable advantage of this procedure is its permanent effect and reversibility in theory. In our experience, we had over 500 ADSD patients in the last 5 years. In summary, almost 60% of patients were very satisfied, 30% felt reasonably satisfied and 10% were unsatisfied with the results. Patients who were unsatisfied with the results complained about a strangulated or breathy voice so that BTX injection or voice therapy was needed for some of those patients. 1% of patients needed removal of titanium implant due to severe breathy voice. We have never experienced dislocation of titanium bridges, but a small number of fractures were detected by regular CT scan several years after surgery. Even when titanium bridges were fractured, the voice never went back to the preoperative status since scar formation surrounding the titanium bridges altered their role. Based on our experience, Type 2 Thyroplasty is highly effective in patients for whom BTX was effective. However, it was less effective for the patients with mixed SD and ADSD with tremor. This surgery is not appropriate for abductor spasmodic dysphonia since it makes the glottal gap wider.
As far as we know, Type 2 Thyroplasty has been done as a standard therapy for ADSD patients only in Japan. Our facility is focused on thyroplasty surgeries which were invented by Isshiki, and is dedicated to treatments for any patients with voice disorders. I hope this article helps further the understanding of Type 2 Thyroplasty. We have been accepting patients from all over the world. Please feel free to contact us if you are interested in this procedure via e-mail hiroshiba.ent.toya@gmail.com.
