Quantitative Evaluation of the Onset and Longevity of the Action of IncobotulinumtoxinA by Skin Displacement Analysis in the Treatment of Glabellar Frown Lines

September 2014 | Volume 13 | Issue 9 | Original Article | 1067 | Copyright © 2014

Thomas M. Proebstle MD PhD,a Gary Chung MS,b Ruth Weissberg MD,c and Tatjana Pavicic MDd

aDepartment of Dermatology, University Clinic of Mainz, Mainz, Germany
bIndependent Contractor, Jamby, LLC, Irvine, CA
cPraxis für Allgemeinmedizin, Munich, Germany
dDepartment of Dermatology, Ludwig-Maximilian-University, Munich, Germany

Abstract

BACKGROUND: A quantitative numerical method for assessing the extent and duration of the inhibitory action of botulinum neurotoxin type A on mimetic muscles would potentially enable more detailed evaluation of the overall efficacy of this aesthetic treatment.
AIM: To evaluate skin displacement analysis (SDA) as a tool for assessment of the extent and duration of effect of incobotulinumtoxinA on mimetic muscles in the glabellar region in routine daily practice.
METHODS: A total dose of 30 U incobotulinumtoxinA was injected into the fronto-glabellar region of 16 subjects. SDA was performed at baseline and during onset and recovery from incobotulinumtoxinA treatment at various timepoints up to 24 weeks after treatment. The reference point for SDA was located at the upper margin of the eyebrow, 30 mm lateral to the median line. To correlate and validate SDA results, semi-quantitative wrinkle score assessments were performed in parallel.
RESULTS: At baseline, the mean horizontal skin displacement was 5.4 mm (standard deviation: ±1.4 mm). During onset of action after treatment, skin displacement values decreased from baseline (100%) by 46%, 85%, and 90% at day 2, week 1, and week 2, respectively. During recovery from incobotulinumtoxinA action, skin displacement values increased to 33%, 50%, and 93% of the baseline value at 6, 12, and 24 weeks after treatment, respectively. The inhibitory effect of incobotulinumtoxinA was highly variable among subjects, ranging from 25% to 68% of the baseline value 12 weeks after treatment. Overall agreement between SDA values and wrinkle scores was good.
CONCLUSION: SDA represents a novel, objective method for the quantitative evaluation of the effect of incobotulinumtoxinA on mimetic muscles underlying the fronto-glabellar region, and showed good correlation with wrinkle score assessments. Both SDA and wrinkle score indicated the persistence of treatment effects 24 weeks after injection.

J Drugs Dermatol. 2014;13(9):1067-1072.

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INTRODUCTION

The use of botulinum toxins to improve the aesthetic appearance of facial features spans more than two decades.1 Assessment of the duration of botulinum toxin action on target muscles, a key attribute of the toxin type that is of value and interest to clinicians and subjects alike, has been hampered by the lack of a quantitative evaluation tool. A number of semi-quantitative tools have been developed,2-6 but all rely on a degree of subjectivity, making it difficult to compare results between studies.

In neurologic indications for botulinum toxins, electromyography (EMG) represents the 'gold standard' for the detection of muscular activity; however, the spatial resolution of this method probably limits its usefulness in aesthetic applications. Despite this, it has been used to assess the overall effect of botulinum neurotoxin type A (BoNT/A) after injection in the frontalis muscle.7 Subjective assessments of wrinkle severity (such as the wrinkle scoring system described by Kim et al5) have been used to compare the effects of different botulinum toxins and dosages.8,9

Skin displacement analysis (SDA) involves quantitative assessment from digital photographs of the skin displacement that results from contraction of the underlying muscles relative to a fixed marker. High accuracy (to within a few millimeters) has been reported for the evaluation of horizontal contraction in the fronto-glabellar area following injection with BoNT/A.10 The aims of this study were to evaluate SDA as a tool for the assessment of the effect of incobotulinumtoxinA on mimetic muscles, and to correlate SDA values with scores obtained using a semiquantitative wrinkle severity score.

METHODS

Study Design

Individuals requesting BoNT/A treatment for glabellar frown lines and forehead lines also aiming for a brow lift in routine daily practice were invited to participate in this investigator-initiated study. To be eligible for the study, subjects were required to be between 18 and 70 years of age. They had to be able

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