Use of AbobotulinumtoxinA for Cosmetic Treatments in the Neck, and Middle and Lower Areas of the Face: A Systematic Review

AbobotulinumtoxinA (aboBoNT-A) has been used for various cosmetic purposes, including minimization of moderate to severe lines, or other cosmetic indications, in the face and neck. We carried out a systematic review to identify all relevant evidence on the treatment approaches and outcomes of aboBoNT-A as a cosmetic treatment of the middle and lower areas of the face, and the neck. Embase, MEDLINE, Cochrane Library, congress proceedings and review bibliographies were searched for relevant studies. Identified articles were screened against pre-specified eligibility criteria. Of 560 unique articles identified, 10 were included for data extraction (three observational studies, 1 randomized controlled trial [with two articles] and five non-randomized trials). The articles provided data on gummy/asymmetric smile (2), marionette lines (5), masseter muscle volume (2), nasal wrinkles (2), perioral wrinkles (3) and the platysma muscle (4). All articles reporting on efficacy of aboBoNT-A demonstrated positive results, including reduction of wrinkles (5), reduction of masseter muscle (2) and degree of gummy smile (1) compared with before treatment. No serious adverse events were reported and patient satisfaction was high. In conclusion, positive findings support further research of aboBoNT-A for the middle and lower areas of the face, and in the neck, which are largely unapproved indications.

Toxins 2021, 13 For aesthetic treatment, aboBoNT-A (Dysport 300 unit vial [Speywood units]) is approved in the USA by the Food and Drug Administration for the temporary improvement in the appearance of moderate to severe glabellar lines associated with procerus and corrugator muscle activity in adult patients less than 65 years of age [10]. In the EU, it is indicated (Azzalure 125 unit vial) for the temporary improvement in the appearance of moderate to severe glabellar lines seen at frown and/or lateral canthal lines seen at maximum smile, in adult patients less than 65 years, when the severity of these lines has an important effect on the psychological well-being of the patient [13]. It is approved in many other countries worldwide for glabellar lines and other aesthetic indications, although it is common for physicians to use aboBoNT-A to treat wrinkles and lines in other areas of the face and neck [14,15]. Several consensus recommendations for the use of aboBoNT-A for treatment of wrinkles or other cosmetic indications on the middle and lower face, and neck and chest have been developed [4,14,16,17]. These recommendations provide information on the number and location of the injection points, the dose of individual injection points, the combined dose of multiple injection points, the injection technique and safety concerns for each area [4,14,16,17].
Owing to its approved indications, most research on the cosmetic use of aboBoNT-A is in relation to glabellar lines and the upper area of the face [18][19][20]. As such, there is a paucity of research on the use of aboBoNT-A in the middle and lower regions of the face and in the neck. The aim of this systematic literature review (SLR) was to assess the evidence regarding treatment approaches, efficacy, safety and patient-reported outcomes relating to aboBoNT-A for cosmetic treatment for several indications for which aboBoNT-A is largely unapproved, namely, treatment of the neck and of middle and lower areas of the face.

Systematic Review of the Literature
A total of 625 papers were identified in the electronic database searches; 65 duplicate papers were excluded before citation screening and 510 papers were excluded during citation screening (Figure 1). There were no relevant studies identified in the supplementary searches, and 40 of the remaining 50 papers were excluded during full-text review, leaving 10 studies (three observational studies [OSs] [21][22][23], five non-randomized controlled trials [24][25][26][27][28] and two studies reporting data from one randomized controlled trial [RCT] [29,30]) included in the SLR. In the included studies, sample size ranged from 10 to 383 patients, mean age was 32.8 to 55.9 years and percentage of female participants was 92.7% to 100% across six studies that reported gender. Three studies were conducted in Brazil [22,29,30], two in Lebanon [24,26], two in the USA [21,27] and one each in South Korea [25], Taiwan [28] and Thailand [23]. Six of the studies looked at aboBoNT-A injections in various parts of the middle and lower regions of the face for the treatment of various conditions, including lower eyelid wrinkles, nasal wrinkles, platysmal bands at rest and at maximal contraction and marionette lines [23,24,26,27,29,30]. Of the remaining four studies, two looked at patients that received injections in the masseter muscles [25,28], one looked only at treatments for excessive gingival display (gummy smile) [22] and one looked at injections in the platysma muscle only [21].

Treatment Approaches
Treatment approaches are summarized, by study, in Table 1, and by indication, in Table 2 and Figure 2. All except one study [27] included approaches to toxin dilution. In eight studies, aboBoNT-A was diluted in saline to produce concentrations ranging from 70 to 250 U/mL (most often 2 or 2.5 mL normal saline to dilute 500 U of aboBoNT-A) for different indications (Figure 2) [21][22][23][24][25][26]29,30]. In one study, aboBoNT-A was diluted in sterile distilled water to produce a concentration of 200 U/mL for the reduction of masseter muscle volume [28]. Table 1 provides details of the specific areas injected in each study. Participants were injected in one [22,27,28] or two [24,25,29,30]  studies did not report injection frequency [21,23,26]. Only one study reported the use of topical anaesthesia, in which patients were treated with a cream containing lidocaine and prilocaine before injection [22]. The number of injection points varied with area of treatment, ranging from two for treatment of anterior gummy smile [22] to 12 for injections into the platysma muscle [21]. In one study looking at injections for rejuvenation of the neck using a multiple-injection technique, participants received approximately 150 micro injections (mean total dose of 154 U aboBoNT-A) across the anterior region of the neck [26].
study design (non-randomized controlled trial/modeling study/case series or studies), (7) study not in English, (8) in vitro/animal study and (9) website source. Narrative reviews were included for first screening so that any relevant cited studies could be identified and were excluded at full-text review.

Treatment Approaches
Treatment approaches are summarized, by study, in Table 1, and by indication, in Table 2 and Figure 2. All except one study [27] included approaches to toxin dilution. In eight studies, aboBoNT-A was diluted in saline to produce concentrations ranging from 70 to 250 U/mL (most often 2 or 2.5 mL normal saline to dilute 500 U of aboBoNT-A) for different indications (Figure 2) [21][22][23][24][25][26]29,30]. In one study, aboBoNT-A was diluted in sterile distilled water to produce a concentration of 200 U/mL for the reduction of masseter muscle volume [28]. Table 1 provides details of the specific areas injected in each study. Participants were injected in one [22,27,28] or two [24,25,29,30] treatment sessions; three studies did not report injection frequency [21,23,26]. Only one study reported the use of topical anaesthesia, in which patients were treated with a cream containing lidocaine and prilocaine before injection [22]. The number of injection points varied with area of treatment, ranging from two for treatment of anterior gummy smile [22] to 12 for injections into the platysma muscle [21]. In one study looking at injections for rejuvenation of the neck using a multiple-injection technique, participants received approximately 150 micro injections (mean total dose of 154 U aboBoNT-A) across the anterior region of the neck [26].

Efficacy Outcomes
Of the included studies, eight reported efficacy outcomes associated with aboBoNT-A treatment to the neck or lower and middle areas of the face (     [23]. 1 Dose was reported in nine out of 10 included studies. 2 Number of injections was reported in seven out of 10 included studies.

Efficacy Outcomes
Of the included studies, eight reported efficacy outcomes associated with aboBoNT-A treatment to the neck or lower and middle areas of the face (Table 3) [22][23][24][25][26][27][28]30]. In six studies that reported timing of clinical effects, improvement was observed at different follow-up times for different treatment areas [23][24][25]27,28,30]. In one study looking at aboBoNT-A treatment in mid-face lifting (involving injection in the platysma muscle and orbicularis oculi), clinical effect was instantaneous in some cases, but in most cases, changes occurred at 5-10 days [23]; whereas in another study of the effect of aboBoNT-A treatment on lower eyelid wrinkles, nasal wrinkles, malar wrinkles, perioral wrinkles, marionette lines, gummy/asymmetric smile and cellulitic chin, improvement was observed at the first follow-up 4 weeks following treatment [30]. Chang et al. also reported an effect of aboBoNT-A treatment on the magnitude of strain in the cheek, marionette lines, nasolabial folds, oral commissures, upper lip and perioral region as a whole, at the first follow-up 2 weeks following treatment [27]. For reduction of masseter muscle volume, clinical effect of aboBoNT-A treatment was observed from 2 to 4 weeks [25,28], and for jowls, platysmal bands, marionette lines, neck volume and oral commissures, improvement was observed at the 15-and 30-day follow-up visits [24].    A duration of action for aboBoNT-A treatment of 3-5 months was reported for gummy smile [22], 10-14 weeks for mid-face lifting involving injection of the platysma and lateral part of the orbicularis oculi [23] and improvement was observed up to 20 weeks following aboBoNT-A treatment of wrinkles in the middle and lower face [30] and up to 90 days following aboBoNT-A treatment of marionette lines [27]. One study of aboBoNT-A treatment for reduction of masseter muscle volume also reported maximum effect at 10-12 weeks following treatment [25].
All eight studies reported improvements following aboBoNT-A treatment in the neck, and middle or lower face [22][23][24][25][26][27][28]30]. Two studies that analysed patients from the same study sample (n = 30 [100% women]) demonstrated significant improvements in scores on a photonumeric scale [31,32] when measuring wrinkles/lines in the platysmal bands at 15 days following treatment compared with before treatment [24,26]. Two studies, a non-randomized controlled trial (n = 32 [100% women]) [27] and an RCT (n = 85 [82 women; 3 men]) [30], showed reductions in the magnitude of strain in the marionette lines, perioral area and chin, at follow-up times of 2-4 weeks. Improvements were also demonstrated, in single studies, for jowls [26], lip [27], and eyelid and nasal wrinkles [30]. Two studies investigated the change in masseter muscle volume at 3 months after injection with aboBoNT-A [25,28]. Kim [28] both demonstrated reductions in masseter muscle volume by approximately 30%; these studies used an ultrasonogram and computed tomography (CT) scan, respectively, to measure muscle volume. Finally, one study investigated the degree of gum display in 16 participants with gummy smile [22]. Findings showed that there were improvements in anterior, posterior, mixed and asymmetric gummy smile of 61-96%, at follow-up 20-30 days following treatment.

Safety Outcomes
Nine studies reported on the safety outcomes associated with the injection of aboBoNT-A in the neck, and upper, middle and lower areas of the face (Table 3) [21][22][23][24][25][26][27][28]30]. The adverse events (AEs) or temporary side effects associated with aboBoNT-A treatment were mild or moderate and occurred infrequently, as follows: injection-point ecchymosis [24,26,33]; lip/face asymmetry [22,23,28,30]; difference in crunching power [25,28]; mild dysphagia following injections in the neck [24,26]; excessive perioral weakness [30]; minor neck muscle weakness [24]; unnatural smiling appearance [25] and disappearance of facial dimple [25]. One of the studies observed AEs under a novel technique, micro injections [26], and the Nefertiti technique [34]. More events of ecchymosis were observed with the Nefertiti technique than with the micro injections (n = 6 vs. n = 3) and mild dysphagia was observed with the Nefertiti technique but not with micro injections [26]. Two studies reported that there were no AEs associated with aboBoNT-A treatment [21,27]. Three studies assessed pain after injection using patient-rated scales [24,26,28]. Mean visual analog scale (VAS) scores for pain from injections ranged from 0.6 to 4.6 on scale of 0 to 10 [24,26], and a mean score of 3 was reported in one study using VAS scores of 1 to 5 [28].

Patient Satisfaction and Quality of Life
Six studies reported patients satisfaction outcomes [22,[24][25][26][27]29] and one study assessed health-related quality of life (Supplementary Materials Table S1: Summary of patient satisfaction and quality of life outcomes) [29]. Most studies used simple surveys, asking the patient whether they were satisfied with their results. Only one study [27] used a formal assessment that has been evaluated elsewhere: the FACE-Q survey [33,35,36]. Five studies showed that 84-100% of participants were satisfied with the results of their treatment (Figure 3) [22,[24][25][26]29]. In one study, the participants were 22.2% (p = 0.014) more satisfied with their overall facial appearance at day 14 compared with baseline [27]. In one study that used two techniques, 72% of patients preferred micro injections, 20% preferred the Nefertiti technique and 8% had no preference [26]. In the study that assessed quality of life, which used the World Health Organization Quality of Life-Brief Version questionnaire (WHOQOL-BREF), there was a significant improvement in the physical quality of life domain between baseline and 4 weeks. When comparing total dose groups, a medium dose group (166-205 U) had significantly better physical, psychological and social relationships quality of life scores than the low (120-165 U) and high (206-250 U) dose groups [29].
formal assessment that has been evaluated elsewhere: the FACE-Q survey [33,35,36]. Five studies showed that 84-100% of participants were satisfied with the results of their treatment ( Figure 3) [22,[24][25][26]29]. In one study, the participants were 22.2% (p = 0.014) more satisfied with their overall facial appearance at day 14 compared with baseline [27]. In one study that used two techniques, 72% of patients preferred micro injections, 20% preferred the Nefertiti technique and 8% had no preference [26]. In the study that assessed quality of life, which used the World Health Organization Quality of Life-Brief Version questionnaire (WHOQOL-BREF), there was a significant improvement in the physical quality of life domain between baseline and 4 weeks. When comparing total dose groups, a medium dose group (166-205 U) had significantly better physical, psychological and social relationships quality of life scores than the low (120-165 U) and high (206-250 U) dose groups [29].  [26]; Hexsel et al. [29]; Mazzuco and Hexsel [22]; Kim et al. [25]; Jabbour et al. [24].

Discussion
To our knowledge, this is the first published SLR describing the evidence on the treatment approaches, efficacy and safety outcomes associated with the use of aboBoNT-A specifically for cosmetic treatment of the neck, and middle and lower areas of the face.
This SLR identified several studies reporting a range of treatment approaches and provides insight into the dose, number of injection points, injection frequency and toxin dilution for aboBoNT-A treatment of the lower and middle areas of the face and the neck. A broad range of treatment approaches were reported, although there were some commonalities amongst some studies, for example in the aboBoNT-A dilution used (2 or 2.5 mL of normal saline to dilute 500U of aboBoNT-A).
A broad range of efficacy outcomes were measured in the different studies; measures to examine improvement following treatment included validated photonumeric scales, digital image correlation and clinician assessment of photographs. To enable the comparison of data across studies, further research using comparable outcome measures would be beneficial.

Discussion
To our knowledge, this is the first published SLR describing the evidence on the treatment approaches, efficacy and safety outcomes associated with the use of aboBoNT-A specifically for cosmetic treatment of the neck, and middle and lower areas of the face.
This SLR identified several studies reporting a range of treatment approaches and provides insight into the dose, number of injection points, injection frequency and toxin dilution for aboBoNT-A treatment of the lower and middle areas of the face and the neck. A broad range of treatment approaches were reported, although there were some commonalities amongst some studies, for example in the aboBoNT-A dilution used (2 or 2.5 mL of normal saline to dilute 500U of aboBoNT-A).
A broad range of efficacy outcomes were measured in the different studies; measures to examine improvement following treatment included validated photonumeric scales, digital image correlation and clinician assessment of photographs. To enable the comparison of data across studies, further research using comparable outcome measures would be beneficial.
All studies identified in this SLR reported that aboBoNT-A treatment is effective for cosmetic use, regardless of the indication. Studies that asked if patients were satisfied with the results of aboBoNT-A treatment showed a high proportion of positive responses. It is not clear from the evidence if satisfaction is driven by the results themselves, onset or duration of results, or all of the above. In this review, five of ten studies reported duration of action for aboBoNT-A treatment and found that duration of action was 2-5 months across various indications [22,23,25,27,30]. This is similar to findings from an international expert consensus on both facial rejuvenation and primary hyperhidrosis, which stated that duration of aboBoNT-A effect was up to 4-6 months for repeated treatment, and could be more than 6 months in some cases [16]. In addition, a systematic review of aboBoNT-A treatment of the upper face found that a typical duration of action was 4 months, across 18 studies [37]. Data on pain experienced during injection were limited, with only three studies reporting this outcome. In addition, only one study examined quality of life outcomes [29].
No serious AEs associated with aboBoNT-A use were reported in any of the studies. One potential serious AE associated with cosmetic injection of botulinum toxins is dysphagia, which can occur as a result of paralysis of muscles near the injection area [38]. Only one case of dysphagia was reported among the ten studies in the current review and its severity was mild. Possibly this is owing to the dose levels among these studies, as risk of dysphagia may depend on dose [39].
A strength of this SLR is that no country and date limits were included in the protocol; therefore, the results provide evidence on the global use and treatment patterns of aboBoNT-A for the neck and lower and middle areas of the face.
However, overall, the number of studies identified in the SLR was low, with many studies identified in the electronic searches looking only at upper regions of the face and therefore being excluded during citation screening. The studies were limited to those published in English and further studies in other languages were not included, which may contribute to the amount of published evidence identified in this SLR being low. Furthermore, the low number of studies identified and the broad range of approaches reported, prevent any statistical analysis of the data combined from different studies.
The aim of this systematic review was not to generate data that would be used to seek regulatory approval for the use of aboBoNT-A as a cosmetic treatment of the neck, and middle and lower areas of the face and none of the studies included in the SLR are funded by manufacturers of aboBoNT-A. The SLR was conducted by the investigators with better scientific understanding as the main aim.

Conclusions
The findings of this SLR demonstrate that aboBoNT-A is used for a range of cosmetic treatments in the lower and middle areas of the face, and in the neck, with positive outcomes for patients and a low complication rate. However, the number of studies identified was low and a broad range of approaches was identified. Further research is needed to establish uniform protocols to allow consistent treatment approaches and optimize treatment outcomes for patients.

Search Strategy
The SLR was performed to identify studies relevant to at least one of the following four key areas: (i) treatment approaches, (ii) efficacy outcomes, (iii) safety outcomes and (iv) patient-reported outcomes, including patient satisfaction and quality of life. The literature searches were conducted in August 2019 in the following electronic databases: (1) (Table S2: Searches carried out in: Ovid MEDLINE, all segments, 1946 to present; Embase 1974 to 18 July 2019; and Cochrane (CDSR, DARE, CENTRAL, NHS EED, The HTA database, and ACP Journal Club) 23 August 2019). The SLR is fully compliant with the 2009 Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines [40]. There is no protocol available for this SLR. The bibliographies of pertinent narrative reviews identified in the SLR and proceedings from The American Academy of Dermatology and European Society for Dermatologic Research annual congresses (2017-2019) were searched for relevant studies.

Eligibility Criteria
The title and abstract of identified publications were screened manually against pre-defined eligibility criteria for each objective (Table S3: Eligibility criteria used in the systematic literature review). The searches were limited to human studies published in English. OSs, non-randomized controlled trials and RCTs were included. Narrative reviews were included for the first screening so that the bibliographies could be searched for any relevant OSs, non-randomized controlled trials or RCTs cited; narrative reviews were excluded at full-text review. Full-text versions of all publications meeting the eligibility criteria at first screening were reviewed. Data from eligible studies were extracted manually into pre-defined summary tables.

Data Extraction
Information extracted from relevant studies included study design, context (aims/ objectives, outcomes/endpoint, disease type, sample size, comparator group, followup period), participants (demographics, disease duration), treatment approaches (area, dose and dilution, number of injection points and injection frequency), efficacy outcomes (wrinkle/line assessment, gum display, global aesthetic improvement scale, onset/duration of action), safety outcomes (AEs), patient satisfaction and quality of life.
Author Contributions: H.G., I.G., R.S., I.P. and A.R. contributed to the conceptualization of this review and the writing of the manuscript. All authors have read and agreed to the published version of the manuscript.
Funding: This study was sponsored by Ipsen.

Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Patient consent was not necessary because content is based on data that are already published.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.