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25 patients were found who had a primary diagnosis of VT and had received LBTX. Four patients were excluded because they did not have adequate follow-up data. Of the remaining 21 patients, 13 patients had a minor pro fi le of spasmodic dysphonia (62%). Fourteen patients (67%) had documented vertical and horizontal tremor. Two patients (9.5%) had documented horizontal tremor only. Five patients (24%) did not have documentation to support any differentiation of their tremor type. Six patients (29%) were documented to have a pharyngeal tremor in addition to their laryngeal tremor. Tongue base and lip tremors were seen in two patients (10%), whereas hypopharynx and jaw tremors were each seen in one patient (5%). Three patients (14%) demonstrated a palatal tremor. All patients were female, with a mean age of 69 years at time of fi rst injec tion (range, 43 – 91 years). Sixteen patients (76%) were also seen by a neurologist for their tremor, and 15 (71%) were trialed on medical therapy. A summary of patient charac teristics can be found in Table I. The median time until follow-up for each injection was 119 days (range, 55 – 878 days). For injections with available postprocedural CAPE-V and VHI-10 data, the median time until follow-up was 119 days (range 70 – 392 days). Injection Outcomes These 21 patients were treated with a total of 49 injections with adequate follow-up data. Any injections TABLE I. Patient Characteristics Including Age at First Injection and Tremor Characteristics.

with VT and those who had received LBTX. As these codes pull a broad range of diagnoses, each chart was individually reviewed to identify patients with a primary diagnosis of VT. Of note, some patients had concurrent spasmodic dysphonia; however, they were only included if spasmodic dysphonia was a minor component of their presentation and tremor the predominant pro fi le. Only patients who underwent bilateral LBTX injections were included. Onabotulinum toxin A (Allergan Pharmaceuticals, Dublin, Ire land) was used for LBTX. Injections were performed by experi enced providers at our institution, and patients underwent transcricothyroid injection of their thyroarytenoid muscles using electromyography (EMG) guidance. Some patients underwent con current injection of their strap muscles if they demonstrated verti cal tremor on laryngoscopy and palpation of the thyroid cartilage during sustained phonation. The strap muscles were injected in the region overlying the thyroid lamina in one location on each side, speci fi cally targeting the sternohyoid and thyrohyoid mus cles. This was performed by palpating the thyroid lamina with the tip of the needle and withdrawing slightly prior to injection. EMG was not used for guidance due the ease of landmark identi fi cation. At each visit a variety of measures were used to identify per ceived bene fi t from each injection. Patients were asked if they received any bene fi t from their injection on a binary scale of yes/no. They were then asked to provide a subjective improvement score on a scale of 0% to 100%, 0% being no bene fi t and 100% being complete resolution. Additionally, baseline scores for the Voice Handicap Index-10 (VHI-10) and Consensus Auditory Perceptual Evaluation of Voice (CAPE-V) were obtained prior to any injection and were obtained again at the time of each injection. These mea sures are obtained for all patients receiving LBTX at our institu tion, and not just limited to those with VT. These scoring methods were chosen to assess both subjective and objective outcomes. Because the effects of LBTX are not immediate, to determine bene fi t from a single injection, the VHI-10 and CAPE-V scores were obtained at the subsequent follow-up, which was typically the following injection. We then determined the difference between these scores and the baseline VHI-10 and CAPE-V scores. Similarly, the patient subjective scores for a given injection were obtained at a subsequent follow-up. For this reason, patients who did not follow up could not be included in our study. istics, and outcome measures were addressed in a deidenti fi ed fashion by a researcher not involved in data collection. Descrip tive statistics were calculated for demographics, baseline mea surements, and tremor characteristics. Comparison of outcome measures using injection locations and the presence of spasmodic dysphonia minor characteristic was conducted for each variable using Wilcoxon rank sum nonparametric testing. Additional ana lyses were conducted on the subgroup of patients who had both horizontal and vertical tremor components, and this subgroup was compared based on the injection location used. Linear and logistic regression modeling was used to assess the effect of injec tion methodology on outcomes for categorical and continuous var iables, respectively. An α level of .05 was considered signi fi cant for all testing. All statistical analyses were conducted using SAS 9.3 (SAS Institute, Cary, NC) and JMP Pro 12.1 (SAS Institute). Statistical Analysis Raw values for all patient characteristics, tremor character

Vertical and/or Horizontal Type

Patient No.

Age, yr

Sex

Tremor Type

1 2 3 4 5 6 7 8 9

65 60 68 44 57 78 84 72 66 72 63 69 85 83 69 91 60 78 81 60 43

F F F F F F F F F F F F F F F F F F F F F

Pure Pure Pure Pure Pure Pure

Both Both Both Both Both Both Both Both Both Both Both Both

Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Tremor plus Pure Pure

10 11 12 13 14 15 16 17 18 19 20 21

Horizontal only Horizontal only

Both

Unspeci fi ed Unspeci fi ed Unspeci fi ed Unspeci fi ed

Both

Unspeci fi ed

RESULTS Patient Characteristics

Pure tremor type indicates features of essential vocal tremor only, whereas tremor plus indicates the patient had an additional minor pro fi le of spas modic dysphonia. The vertical and horizontal nature of tremor is also indicated. F = female; M = male.

Five hundred sixty-one patients were identi fi ed using the selected diagnostic codes. After initial chart review,

Laryngoscope 129: June 2019

Nelson et al.: Strap Muscle Injections for Vocal Tremor

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