Type II Thyroplasty

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.

*This article is modified from the report of NSDA newsletter (2018, Vol. 28).