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TABLE II. Mean Outcomes After Laryngeal Botulinum Toxin Injections.

Subjective Improvement Score

Δ CAPE-V Overall

Δ CAPE-V Roughness

Δ CAPE-V Breathiness

Δ CAPE-V Strain

Δ CAPE-V Pitch

Δ CAPE-V Loudness

Δ VHI

− 1.9 − 2.7 − 1.4

− 7.8 − 3.5

− 4.4

− 19.6 − 185 − 20.3

− 0.4

Overall results

70% 67% 74%

5.7

1.1 − 3 3.5 .68 1.7 0.7 .42 3.6 4.0 3.5 .80

− 7

− 2 0.6 .68 0.0

Received TA only

15.0

− 10.3

− 2.9

Received TA+S

0.3

P value

.70

.64

.10

.09

.94

.78

− 2.5 − 1.3

− 7.1 − 8.3

− 6.7 − 2.7

− 12.5 − 25.3

Patients with pure tremor

60% 74%

9.6 2.7

− 0.7

Patients with minor SD pro fi le

P value

.34

.25

.99

.58

.71

.33

.15

− 1.1 − 0.4 − 1.4

− 9.3 − 6.0

− 3.2 − 4.0 − 2.9

− 18.9 − 14.0 − 20.3

− 0.5 − 4.0

Patients with horizontal + vertical tremor

64% 35% 74%

6.6

Received TA only

28.0

− 10.3

Received TA+S

0.3

0.6 .99

P value

<.005

.64

.41

.06

.87

.67

Results of the overall group are shown with breakdown showing site of injection and purity of tremor. No statistical signi fi cance was found in the overall group between different sites of injection and purity of tremor. When patients with horizontal and vertical tremor were isolated, those who received TA+S injec tions had signi fi cantly better subjective improvement scores. CAPE-V = Consensus Auditory Perceptual Evaluation of Voice; SD = spasmodic dysphonia; TA = thyroarytenoid; TA+S = thyroarytenoid and strap muscle; VHI = Voice Handicap Index.

in their subjective scores compared to those who received TA injections alone. This difference was both clinically and statistically signi fi cant (TA: mean 35%, median 35%; TA+S: mean 74%, median 80%, P < .005) The TA+S group showed a non – statistically signi fi cant decrease in Δ VHI-10 (TA: − 0.4, TA+S: − 1.4, P = .64) and overall Δ CAPE-V score (TA: − 6, TA+S: − 10.3, P = .41) compared to the TA only group. Further breakdown of CAPE-V sub scores can be found in Table II. Overall, patients reported voice side effects, such as a breathy or quiet voice, with 36 injections (73%) that lasted a mean duration of 3.25 weeks after injection time. Swallowing side effects were less common, affect ing only eight injections (16.3%), with a mean duration of symptoms for 1.9 weeks. Of all strap muscle injec tions, four (16.6%) had postinjection dysphagia, lasting for an average of 2 weeks. For TA injections, four reported dysphagia (16.0%) and an average duration of 1.75 weeks. Patient-reported duration of bene fi t was documented for 40 injections (82%), and the mean dura tion of bene fi t was 12.8 weeks (median 12 weeks; range, 3 – 52 weeks). Intrapatient Analysis Ten patients in the study received TA+S injections, all of whom had horizontal and vertical tremor. Of these 10, seven received exclusively TA+S injections, whereas three patients initially received TA-only injections, but were later converted to TA+S. When outcomes from each injection method were averaged, two out of these three patients showed improvement in their subjective scoring with conversion to bimodal injection (Table III).

that did not have any follow-up characterizing their out come were excluded. Binary subjective improvement scores (yes vs. no) were present for all included injections. Forty-six injections had subjective percentage improve ment scores available. To obtain differences in VHI-10 and CAPE-V scores, patients needed to have available baseline scores in addition to follow-up scores. Twenty seven injections (55%) had these data available. Reasons for incomplete VHI-10 and CAPE-V data were multifacto rial. Patients may have been seen by multiple providers prior to LBTX injection, and the baseline data may sim ply have not been collected. Another reason may be related to time constraints and reduced staf fi ng during some clinic visits. Twenty-four injections were of both thyroarytenoid and strap muscles (TA+S), and these were only performed on patients with both horizontal and vertical tremor com ponents. Twenty- fi ve injections were of thyroarytenoid (TA) muscles only, and performed on patients with hori zontal tremor only, horizontal and vertical tremor, and also unspeci fi ed-type tremor. The mean dose of botulinum toxin injected into each TA muscle was 1.2 units (range, 0.5 – 2.5 units ) and the mean dose injected into each strap muscle was 2.3 units (range, 2 – 3 units). The mean total dose was 4.6 units (range, 1.5 – 9.5 units), including both TA and strap muscles bilaterally. Overall, in 48 of 49 injections (98%), patients reported some subjective bene fi t. Of the 46 injections with an available subjective improvement score, patients reported mean improvement of 70% per injection. When available, postprocedural change in VHI-10 and CAPE-V scores were calculated and are reported in Table II. No statistically signi fi cant difference was found between out comes and tremor purity (i.e., presence of a minor compo nent of spasmodic dysphonia). Of patients with both horizontal and vertical compo nents to their tremor (33 injections), patients who received TA+S injections showed signi fi cant improvement

DISCUSSION Vocal tremor is a movement disorder of the larynx that may be associated with essential tremor. Treatment

Laryngoscope 129: June 2019

Nelson et al.: Strap Muscle Injections for Vocal Tremor 1435