Commentary on: Relationship Between Vertical Glabellar Lines and the Supratrochlear and Supraorbital Arteries Free

I read with great interest the article by Cotofana et al¹ on the relation between the vertical glabellar line (VGL) and the supratrochlear arteries (STAs) and supraorbital arteries (SOAs). In recent years, many articles have been published on this relation and on the glabella in general, from its topographic anatomy to imaging. Much of this work has been motivated by the the glabella’s reputation as a “sinister site” responsible for embolic events caused by soft tissue fillers.

Years of the “reverse pyramidal” phenomenon of the hierarchy of evidence and conflicting hypotheses have left many aesthetic practitioners perplexed as to what is considered to be the standard or the norm. I would like to thank the pioneering research, both laboratory and clinical, conducted by this article’s authors, who are changing the shape of modern aesthetic practices. The authors should be credited for undertaking such an endeavor.

I will now dive deep into this article with a logical and systematic appraisal. The authors used ultrasound imaging on healthy individuals to investigate the course of the superficial branch of the STA and the deep branch of the SOA in relation to the ipsilateral VGL. This was based on a similar study of Doppler imaging on 19 healthy volunteers, 8 of whom were injected cephalically; the authors of that study concluded that glabellar frown lines could be a reliable landmark for STA vascular pedicle (SVP) localization when creating a midline forehead flap.² Subsequently, in the later part of the discussion, the authors linked recent research on the relation between wrinkles and lymphatic vessels that were found above and within ±1 mm of a major lymphatic vessel.³ This resulted in the construction of present null hypothesis by Cotofana et al that “injections of soft tissue fillers away from the crease are safe,” which was not suggested by Vural et al and Pessa et al as mentioned earlier.^2,3

Cotofana et al state in their well-written introduction that the retinal arteries are connected to the branches of the external carotid artery (ECA) system and its branches to the contralateral side. However, I would like to add that the retinal arteries (only referred to as the central artery of the retina and its branches to the 4 inner-layer retinal quadrants) are end arteries without any direct communication to the ECA system; visual compromise occurs due to the retrograde flow of soft tissue filler materials into the ophthalmic artery system through its anastomotic connections to the ECA system.^4,5

An appraisal of the Methodology section raises a few questions. First, participants with any type of disease affecting the integrity of the facial anatomy were excluded. Perhaps the authors could have listed those diseases. Second, the sample size calculation was not mentioned; however, without an appropriate power, the study is subject to type 2 errors. Third, for ultrasound imaging to be reliable, reproducible, and relevant, one has to ensure that the position (of the patient), the placement (of the transducer), and the precision (experience) is consistent and recorded. Because the volunteers were seated in an upright position, visualization of the vasculature without applying pressure is challenging, and even a minute movement of the unsupported head can lead to some inaccuracies. In the article, the investigators’ knowledge of the vascular anatomy, along with its variations and the sonographic experience, is not clear to me as a blinded reviewer. Fourth, the repeated subsample measurement to calculate the reliability (intraclass correlation coefficient, 0.938) does not nullify all the confounding arising from single-observer bias. Perhaps it would have been better to have 2 investigators and to utilize Cohen’s κ coefficient for agreement between them to test whether the concordance is higher than chance alone. Moreover, recognizing the profound importance of vascular and related measurements, the standard error of measurement could have been calculated, thus providing an absolute index of measurement, unlike intraclass correlation coefficients. Finally, to determine the investigators’ and participants’ contribution to bias, a variance components analysis would have made this study more robust.

Instead of analyzing the Results section, it would have made more sense if the current findings had been compared with recent similar literature regarding the diameter, depth, and position of the vessels. The main point of the discussion is the position of the VGL and its relation with the STA and the SOA. The distance between the VGL and midline was reported to be 9.3 ± 2.5 mm by Vural et al.² However, in the present study, it was 5.55 ± 1.8 mm. Even the STA was found to be much closer to the VGL than the current study. One can also observe the fact that the depth, diameter, and distance varied significantly in recent studies.^6-9 This may be indicative of anatomic variation due to ethnicity. However, I do believe that citing the current literature would have strengthened the present study through comparing and contrasting the findings.

Frowning makes the VGL and vessels shift more medially because facial soft tissues are more dynamic. However, the critical question is how frowning would affect the static glabellar line when it is treated with soft tissue filler. If one presented with a static line in the glabella, typically the most effective method is to place soft tissue filler intradermally. According to this study, if the mean depth of the STA is 3.34 ± 0.6 mm, intradermal injection by an expert hand would not be an issue. Nevertheless, I agree with the authors’ statement about injecting neuromodulators before placing the soft tissue fillers because it would “reposition” the vessels.

I do not intend to be unenthusiastic in my commentary because I wholeheartedly agree that the observations made in this paper bear much relevance in aiding the use of safer injection techniques among aesthetic practitioners. However, I failed to elucidate any new contribution in light of the recent evidence cited above, apart from anatomic variations due to ethnicity. I wish to thank the authors again for reinforcing the importance of the vascular anatomy around the glabellar complex, along with its related clinical implications. As written in Genesis, “Let there be light.”

Disclosures

The author declared no potential conflicts of interest with respect to the research, authorship, and publication of this article.

Funding

The author received no financial support for the research, authorship, and publication of this article.

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