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Laryngeal Botulinum Toxin Injection for Vocal Tremor: Utility of Concurrent Strap Muscle Injection

Rebecca Chota Nelson, MD; Valeria Silva Merea, MD; William S. Tierney, MD; Claudio Milstein, PhD; Michael S. Benninger, MD; Paul C. Bryson, MD

Objectives/Hypothesis: Vocal tremor is a neurologic disorder that can be treated with laryngeal botulinum toxin injec tions (LBTX). We sought to describe our experience with thyroarytenoid and concurrent strap muscle injection. Study Design: Retrospective chart review. Methods: A chart review was performed of all patients with a primary diagnosis of vocal tremor treated with LBTX from 2012 through 2017. Results: Twenty-one patients were included (mean age 69 years, 100% female). Thirteen patients (62%) had a minor component of spasmodic dysphonia in addition to their tremor. Fourteen patients had vertical and horizontal components to their tremor, and two had horizontal tremor alone. The remaining fi ve patients did not have clear characterization of their tremor. A total of 49 injections were reviewed (25 thyroarytenoid [TA], 24 thyroarytenoid and strap muscle [TA+S]), and patients reported subjective voice bene fi t with 48 (96%) of these (92% TA, 100% TA+S). When available, the postprocedural change from baseline Voice Handicap Index-10 and Consensus Auditory Perceptual Evaluation of Voice scores were calculated (mean overall: − 1.9, − 7.8; TA: − 2.7, − 3.5; TA+S: − 1.4, − 10.3, respectively). Subjective patient improvement ratings (scale 0% – 100%) were obtained for 46 injections, with a mean of 70% improvement per injection. Of patients with both horizontal and vertical tremor, outcomes were improved with TA+S injection versus TA alone (mean improvement 74% vs. 35%, P < .005). Conclusions: There is utility in the characterization of vertical and horizontal components of vocal tremor. Patients with both appear to have increased bene fi t with injection of strap muscles in addition to thyroarytenoid muscles. Key Words: Vocal tremor, laryngeal botulinum toxin, neurolaryngology. Level of Evidence: 4 Laryngoscope , 129:1433 – 1437, 2019

INTRODUCTION Vocal tremor (VT) is a neurologic disorder character ized by involuntary and rhythmic movement of the laryn geal musculature, classically at 4 to 12 Hz, and is often thought of as a potential phonatory manifestation of a global neurological disorder: essential tremor. 1 Essential tremor is a common adult-onset movement disorder, with laryngeal involvement in as many as 30% of affected patients. 1,2 Additionally, VT is not always limited to the intrinsic muscles of the larynx, but may also involve extrin sic laryngeal, pharyngeal, and palatal musculature. 2 There are two well-described subtypes of VT: horizontal vocal tremor and vertical vocal tremor. 3 – 6 The former describes oscillatory movements in the horizontal plane, which are predominantly mediated by the thyroarytenoid and lateral cricoarytenoid muscles. Vertical tremor describes vertical plane oscillation of the laryngopharynx, which can be From the Head and Neck Institute, Cleveland Clinic Foundation, Cleveland, Ohio, U.S.A. Editor ’ s Note: This Manuscript was accepted for publication September 9, 2018. Presented at the American Laryngological Association Meeting at the Combined Otolaryngology Spring Meetings, April 18 – 22, 2018. The authors have no funding, fi nancial relationships, or con fl icts of interest to disclose. Send correspondence to Rebecca Chota Nelson, MD, Head & Neck Institute – A71, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195. E-mail: nelsonr4@ccf.org

mediated by a variety of extrinsic laryngeal muscles includ ing strap musculature. 4 The therapeutic decision tree for VT is complex, with options that include voice therapy, medical therapy, vocal fold augmentation, or laryngeal bot ulinum toxin injection (LBTX), with roles for speech pathol ogists, neurologists, and laryngologists. 2,5,7 – 10 There is, however, a growing body of evidence for the role of LBTX therapy. 3 – 6,11 Although treatment paradigms exist describ ing differing injection sites for both horizontal and vertical tremor, namely thyroarytenoid muscle injections for horizon tal tremor and strap muscle injections for vertical tremor, there is little published on the outcomes of these injection sites based on these characteristics of vocal tremor. 4,5 Our study aimed to measure outcome differences when different sites of injection are chosen based on a horizontal or vertical tremor pro fi le. MATERIALS AND METHODS Institutional review board approval was obtained prior to commencement of this study. A retrospective chart review was performed by reviewing patients with diagnostic codes for laryn geal spasm ( International Classi fi cation of Diseases, Ninth Revi sion, Clinical Modi fi cation [ICD-9-CM] 478.75/ International Classi fi cation of Diseases, Tenth Revision, Clinical Modi fi cation [ICD-10-CM] J38.5) and vocal tremor (ICD-9-CM 784.49/ICD 10-CM R49.8) who were seen by our senior authors ( P . C . B ., C . M ., or M . S . B .) from January 2012 through September 2017. Based on cod ing practices at our institution, this was felt to capture all patients

DOI: 10.1002/lary.27631

Laryngoscope 129: June 2019

Nelson et al.: Strap Muscle Injections for Vocal Tremor 1433

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