DaxibotulinumtoxinA Injection for Treatment of Adductor Spasmodic Dysphonia

Spasmodic Dysphonia (SD) is a neurologic condition causing inappropriate contraction of the laryngeal musculature, leading to abnormal voicing. The three types (adductor, abductor, and mixed) affect varying muscle groups which produce characteristic voice patterns. The vast majority of patients with SD have adductor type, which impacts the lateral cricoarytenoid and thyroarytenoid muscle complex. While many treatment modalities have been investigated, the most effective treatment is botulinum toxin injection to these muscle groups, performed transcervically with or without electromyography (EMG) guidance. Patients undergoing this treatment typically require re-injection every 3 months. Due to its specialized nature, the laryngeal injections are not performed routinely outside of academic medical centers; thus, patients may come from a distance to receive this treatment. Both due to the significant impact on voice quality when the injections wear off and the sometimes challenging access to treatment, a longer-acting agent is desired. Injectible daxibotuliumtoxinA (DAXI, Revance Therapeutics Inc., Newark, CA) has been shown in large clinical trials to provide safe, effective treatment for glabellar lines and cervical dystonia and may offer a longer-lasting result when compared with onabotulinumtoxinA. Thus, a study examining the effect of DAXI for patients with adductor spasmodic dysphonia is proposed. This study aims to assess the efficacy of DAXI for transcervical laryngeal injection in patients with adductor spasmodic dysphonia.

Injectible daxibotulinumtoxinA (DAXI, Revance Therapeutics Inc., Newark, CA) is an investigational botulinum toxin type A which has been shown in large clinical trials to provide safe, effective treatment for glabellar lines and cervical dystonia and may offer longer-lasting results when compared with onabotulinumtoxinA. Dosage will be same number of units as prior Botox A dose.

This will be determined using a paired t-test with subjects pre-treatment VHI-10 scores as a control.

A secondary outcome will be comparing the duration of effect of DAXI with patients' prior Botox treatment.

Specifically, we will determine the median time to baseline VHI-10 after treatment with DAXI and produce a Kaplan-Meier curve to illustrate the duration of clinical benefit.

Inclusion Criteria: greater than 18 diagnosis of adductor spasmodic dysphonia previous successful treatment with BotoxA stabilized dose for last 3 treatments Exclusion Criteria: age less than 18 exclusively having other neurologic conditions such as: abductor spasmodic dysphonia ALS Multiple sclerosis Parkinson's disease Essential tremor

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