Adductor Spasmodic Dysphonia – Changes in dosing after prolonged injections

Abstract

CONTACT OBJECTIVES: Botulinum toxin therapy (BTX) for adductor spasmodic dysphonia (ADSD) requires re-injection. The dosing effects after prolonged treatment are not well reported. We report our ten-year experience in the utilization of BTX in ADSD STUDY DESIGN: Retrospective chart review METHODS: From a database of 182 ADSD patients from 1997-2008 treated with BTX, we pulled a subset of 87 patients receiving BTX for greater than 3 visits (average 10.27 visits, range 3-40). We analyzed duration of effect, dosing effects and changes in administration technique. RESULTS: This study group was predominantly female (3:1), presenting at mean age 60. All BTX was administered with laryngeal electromyographic guidance. The average starting dose was 2.28 units (range 1.25 – 3.75). The average dose per injection was 2.15 units (range 0.25-12.5) with an average time interval of 5.6 months between visits. Patients reached a stable dosing regimen at an average of 1.34 months, with 75% optimized after the first visit. There was a trend towards increased average dosage for patients during their 15th treatment visit and up (p=0.14), with increased variation in effect (SD 0.95 vs 1.36). Average time interval between visits tended to decrease over time. Patients who began treatment at older ages in the 6th and 7th tended to require decreasing dosages over time. 10 out of 87 patients progressed to unilateral injections after an average of 12.5 treatment visits, with 70% efficacy. CONCLUSIONS: Botulinum therapy in ADSD is stable and safe. Prolonged treatment over 15 visits may require changes in dosing and technique. Unilateral injections provide an effective alternative to bilateral injection. Name: Nina Chinosornvatana, MD Organization: Mount Sinai Hospital Email: nchinos@gmail.com •Patient positioned supine with neck slightly extended. Laryngeal electromyography (LEMG) ground and reference electrodes are placed. Neck prepped. •Botulinum toxin diluted to 100 units per 4cc of injectable bacteriostatic saline. 1cc tuberculin syringe fixed to LEMG monopolar electrode injector needle. •Needle inserted through the skin just off of midline at the level of the cricothyroid membrane. Needle advanced superolaterally towards the targeted thyroarytenoid muscle. •LEMG used to verify placement of needle into thyroarytenoid muscle, showing increased muscle action potential complexes with phonation and cough. •Starting dosage administered is 2.5 units to each side. Subsequent dosing is determined dependent on prior dosage and its effectiveness. • Botulinum therapy was shown to have prolonged efficacy, with successful injections administered at upper limits of 80 injections, 40 visits, and 10 years. This is consistent with BTX’s proven record of safety and efficacy in the literature. To date, there are no reports of mortality attributed to BTX treatment in the literature. 7 The most common adverse effect has been temporary excessive breathiness from overinjection. •We recommend 2.5 units to each thyroarytenoid muscle as an effective starting dose with use of laryngeal electromyographic guidance. Reported rates of starting dosage administration vary; our 70% efficacy rate after the first visit compares favorably to other reported series. 6,7 •We saw an increase in dosage variability in patients receiving prolonged treatment beyond 15 visits, with a trend towards increased average dosing. Other series have reported decreases in dosing requirements over time without resistance. 7 We therefore recommend vigilant attention to changes in dosing requirement or technique in patients over 15 visits, with consideration of unilateral injections as an alternative to bilateral injection. •Unilateral injections have been reported to be successful in a wide range of doses, from 2.5u – 30u. 9 Comparisons to bilateral injections have shown similar efficacy, with some reports of decreased side effect profiles. 10 Our experience confirms unilateral administration as a useful and effective alternative to bilateral injection. •Adductor spasmodic dysphonia (ADSD) is an idiopathic focal dystonia of the intrinsic laryngeal adductor musculature. Spasms most frequently affect the thyroarytenoid muscles, but can also involve the lateral cricoarytenoid and interarytenoids, resulting in overforceful vocal fold closure. •Clinically, ADSD presents with strangulated strained vocal quality, and is characterized by repetitive breaks in phonation and pitch, requiring increased effort during speech. ADSD is triggered by speech, in particular, voiced sounds. 1 •Treatment options for ADSD include speech therapy, recurrent laryngeal nerve sectioning2,3 , partial thyroarytenoid myectomy4, anterior commissure release, and botulinum administration. The use of botulinum remains the gold standard treatment due to its effectiveness, reliability, and high safety profile.5 •Chemodenervation with botulinum requires reinjection. Because there is significant variability in patient response and toxin delivery, individualization of treatment is necessary for optimal effect. Adductor Spasmodic Dysphonia