An Anatomical Approach to Glabellar Rhytids

ORIGINAL ARTICLE An Anatomical Approach to Glabellar Rhytids

Michael R. Macdonald, MD; Jeffrey H. Spiegel, MD; Raymond B. Raven, MD; Sheldon S. Kabaker, MD; Corey S. Maas, MD

Objective: To identify surface landmarks that can serve frontalis, and procerus muscles. as reference points to the underlying musculature in the treatment of glabellar rhytids. Conclusions: The information gained here may be applied to the pharmacological or surgical treatment of gla- Methods: Fifty cadaver hemibrows were dissected to bellar rhytids. Knowledge of the frequent location of the assess the location, disposition, and relationships of muscles involved, relative to easily identifiable surface the brow muscles, along with their variations at each landmarks, allows a more precise approach. of several consistent locations. Particular attention was paid to the corrugator supercilii, frontal belly of the Arch Otolaryngol Head Neck Surg. 1998;124:1315-1320

HE GLABELLA occupies a the skin and factors associated with pho- relatively central position in toaging contribute to rhytid formation but the face and therefore eas- play a much less important role. ily attracts the attention of A variety of direct surgical ap- patients and their observ- proaches have been used for the eradica- ers.T Rhytids in this region, which range tion of glabellar rhytids since the 1920s. from fine lines to deep furrows, may re- This type of procedure allows direct visu- sult in the patient being incorrectly seen alization of the muscles to defunction or as angry, anxious, fatigued, fearful, or of excise them.3,4 The coronal lift has fluc- advanced age. Most commonly, glabellar tuated in popularity during the years.5,6 For rhytids are dynamic in nature. These hy- a long time, it was the only approach for perfunctional lines are a result of the pull elevation of the eyebrows, as well as cor- on the skin by the underlying facial mus- rection of the vertical and horizontal culature.1 This is in contrast to facial wrinkles in the glabella. Suspensive forces wrinkles in other areas, which result from from the forehead lift contributed to mak- age-induced changes in the collagen of the ing the glabellar area smoother, but muscle dermis. While the latter are frequently se- ablation was found to be essential. How- quelae of sun damage and aging in an older ever, patients without brow ptosis or fore- population, hyperfunctional glabellar lines head rhytids, who do not need or want a may be seen in younger patients, aged 20 brow lift, are often reluctant to agree to a to 50 years. coronal incision with its attendant scar- From the Division of Head and Individuals present with different pat- ring, morbidity, and recovery time. Neck Surgery, Department of terns of rhytid formation according to their Postsurgical patients are occasion- Surgery, Alameda County habits of facial expression and resting fa- ally able to contract residual corrugator or Medical Center, Oakland, Calif cial posture. The vertically oriented pro- procerus muscles, either in the early post- (Dr Macdonald); and Division cerus muscle is thought to make the great- operative period7 or within 3 to 4 months.8 of Head and Neck Surgery est contribution to the formation of This produces either a recurrence of the (Drs Spiegel and Raven), horizontal glabellar furrows, while the cor- initial complaint or a localized hornlike Aesthetic Facial Plastic Surgery rugator supercilii muscles produce the ver- prominence along the eyebrow that may Medical Clinic (Dr Kabaker), tical rhytids in this region. There may be be caused by the formation of a scar tis- and Division of Facial Plastic some contribution from a muscle identi- sue “bridge” between divided muscle seg- and Reconstructive Surgery 2 (Drs Kabaker and Maas), fied as the depressor supercilii, but de- ments. Alternatively, this may result from Department of Otolaryngology, scriptions of this muscle are few, bring- incomplete resection or transection of the University of California, ing its existence as a distinct entity into involved muscle groups. In response to this San Francisco. some question. The elastic properties of situation, more direct, limited surgical ap-

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Twenty-six cadavers were selected at random from the University of California at San Francisco Depart- ment of Anatomy Laboratory. There were 12 males and 14 females. Cadavers had undergone preserva- tion in the standard method and had had no previ- ous dissection of the head and neck. Complete dissection of the glabellar region of the first female cadaver was carried out to confirm the relationships between the regional muscle groups. Each remain- ing cadaver provided 2 sets of brow musculature, thus providing 50 hemibrows for evaluation. Methylene blue was used to mark each cadaver Figure 1. Methylene blue markings before cadaveric dissection. along parallel sagittal planes through the midline of the nasal dorsum, the plane of the medial canthus, the plane of the midpupillary lines, and the plane of the lateral canthus (Figure 1). Incisions were made with a sharp No. 10 blade scalpel along these demarcated planes from skin to frontal periosteum (Figure 2). Dissections and measurements were done by a single prosector (M.R.M.) who was blinded to the accumulating results. Measurements were made by means of a steel caliper and steel ruler in millime- ters and included the following: corrugator supercilii depth from skin; corrugator supercilii muscle belly thickness; frontalis muscle depth from skin; procerus muscle length; and procerus muscle depth from skin. The measurements related to the corrugator and frontalis were taken at each of 4 locations (if present): midline, medial canthus, midpupillary Figure 2. Incisions made from skin to frontal periosteum, demonstrating line, and lateral canthus. The procerus muscle was tranverse section of underlying musculature. measured in the midline only. Additionally, the position of the predominant bulk of corrugator polytef, and autologous fat, have been used to lessen the muscle relative to a transverse line through the eye- 10,11 brow was assessed at the plane of the medial can- cosmetic deformity. These treatments do not ad- thus. Random specimens were reevaluated to dress the underlying facial musculature that produces the ensure internal consistency of measurement. Data functional lines. were recorded in preconstructed data tables. Once Botulinum toxin type A (Botox; Allergan Inc, Irv- the measurements were completed, the brow mus- ine, Calif) is a neuromuscular blocking agent that in- culature was dissected to make qualitative observa- duces a flaccid paralysis when injected into striated tions about the relative muscle orientation, posi- muscles.12 This toxin was first used in the 1970s in the tion, origins, and insertions. treatment of strabismus.13 In the 1980s, its use was ex- Statistical analysis of muscle measurements re- panded to the treatment of other facial dystonias, such lied on Student t test (2-tailed) for individual samples. as blepharospasm, hemifacial spasm, and oromandibu- Any missing data were pairwise deleted. In addition 14-16 to comparison among measurements within each cat- lar dystonia. More recently, its use in the treatment egory, measurements in males and females were com- of hyperfunctional lines of the face has been introduced pared across each category. Qualitative observa- as a simple, noninvasive alternative to surgery or fill- tions were, of course, not subjected to statistical ers.17,18 Carruthers and Carruthers17 first advocated its use analysis. However, descriptive trends regarding muscle in the treatment of glabellar frown lines in 1992. This size and position were observed. method has been effective in producing excellent tem- porary results. However, application of botulinum toxin to this area is still in its relative infancy, with precise dos- ing and administration techniques still under active in- proaches have been introduced. Endoscopic techniques vestigation. that use limited hairline incisions and transpalpebral ap- The results of medical and surgical approaches proaches are now advocated for excision of the corruga- have been varied in terms of initial effectiveness and tor or transection of the procerus.8 duration of action. After surgical resection of a portion Other attempts at correction of rhytids in this re- of the involved muscles, a scar may bridge the gap dur- gion have included direct excision, leaving unsightly scars ing the healing process so that reanimation occurs. or abnormal facial motion.9 Alternatively, tissue “fill- Alternatively, the muscle groups that cause the rhytids ers,” such as silicone, collagen, suture material, fibrin, may be incompletely resected. Similarly, under normal

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2 Corrugator Supercilii Depth, mm Corrugator Supercilii 1

0 Midline Medial Canthus Midpupil Lateral Canthus

Figure 3. Initial dissection was performed to identify the relationship Figure 5. Average findings for corrugator depth. between the various muscles in the glabellar region. Here, scissors are passed deep to the corrugator supercilii.

30 3.0 Males Females 25 2.5

20 2.0

15 1.5

No. of Hemibrows 10 1.0

Corrugator Supercilii Thickness, mm Corrugator Supercilii 0.5

0 0 Below Midline Position Above Midline Medial Canthus Midpupil Lateral Canthus Figure 6. Corrugator position relative to a transverse line drawn through the Figure 4. Average findings for corrugator thickness. midhorizontal eyebrow.

circumstances, initial botulinum toxin treatment may RESULTS last from 3 to 6 months.17-20 Failure of botulinum toxin therapy or short duration of action may occur despite Initial dissection of the glabella, to establish the relation- the use of electromyographic (EMG) localization of the ships between the various muscles in this region, is dem- muscle. In this case, the EMG enables nonspecific iden- onstrated in Figure 3. In the medial canthal area of the tification of muscle activity. Even if the EMG is used glabella, the thin frontalis was the most superficial muscle during the appropriate facial expressions to accentuate encountered, with the more bulky corrugator supercilii the rhytids in this area, it does not guarantee proper located deep to it. The corrugator was easily followed as placement of the injected botulinum toxin. Further- it passed along a plane slightly oblique to the horizon- more, the rare complication of upper eyelid ptosis may tal, along the superior orbital ridge. It was identified in be caused by improper placement with migration of the 2 forms. It could be found as a short, narrow pyramidal toxin through the orbital septum so that the levator muscle located at the medial end of the supraorbital ridge palpebrae superioris is affected. For both the surgical or as a long, narrow, straight muscle extending along the and medical approaches, an understanding of the rel- supraorbital ridge to or just beyond the midbrow posi- evant anatomy—the muscles involved and their position. Laterally, it interdigitated with the frontalis muscle tions relative to each other, as well as to adjacent before inserting into the skin of the midbrow or the me- structures—is critical. An accurate knowledge of the dial half of the brow. Medially, the corrugator became specific anatomy relative to surface landmarks is par- confluent with the procerus muscle. No isolated verti- ticularly important when blind or even EMG-guided cal component of the corrugator was identified medi- botulinum toxin injections are used, yet most descrip- ally. The frontalis muscle had a relatively uniform depth tions of this region are vague. and was attenuated in the midline, where it interdigi- The purpose of this study was to examine the tated with the procerus. The procerus muscle was iden- glabellar musculature in detail to provide a clear tified as a small, thin pyramidal muscle arising from the understanding of its relationships to surface land- tendinous fibers that cover the inferior portion of the na- marks. To improve the management of functional sal bone and the upper lateral nasal cartilage. Its inser- rhytids in this area, an accurate knowledge of this tion was into the skin between the eyebrows. Its fibers, anatomy is important. oriented vertically, became continuous above the

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3 10

2 Frontalis Depth, mm Procerus Length, mm 5 1

0 0 Midline Medial Canthus Midpupil Lateral Canthus Males Females

Figure 7. Average frontalis depth. Figure 8. Average procerus length.

nose with the medial fibers of the frontalis. The width of lift, depend on detailed knowledge of the related anatomy the insertion varied and overlapped the medial frontalis to guide direct visualization of the involved muscle groups muscle edges in most specimens. No distinct depressor and avoid the neurovascular “danger zones.” Transcu- supercilii was identified. taneous soft-tissue augmentation or focal paralysis with Average findings for the various measurements are the use of botulinum toxin is performed without this seen in Figure 4 through Figure 8. Corrugator muscle advantage. thickness varied significantly with measurement posi- Thus, anatomical knowledge of the area relies on ap- tion in both male and female specimens. The thickest por- propriate surface landmarks. The nerves of surgical im- tion of the muscle belly was found at the medial can- portance in the area are the supraorbital, supratroch- thus (PϽ.05). Substantial muscle bulk was still present lear, and infratrochlear nerves, and the corrugator at the midpupillary line, but no distinct corrugator fi- supercilii and procerus muscle motor branches.8 Colla- bers were detectable at the lateral canthus or in the mid- gen, autologous fat, and silicone, if injected into the reti- line. When the depth of the corrugator muscle from the nal circulation, may produce embolic necrosis of the retina skin surface was compared, no statistically significant dif- and blindness. This has been reported with injectable col- ferences could be found between medial canthal and mid- lagen21 and autologous fat.22 No embolic damage to the pupillary locations. These results were consistent with retina, optic nerve, or other surrounding structures has qualitative observations from careful dissection of this been reported with the use of botulinum toxin type A. muscle. The muscle was thickest near its periosteal ori- This may be, in part, because this material is completely gin medially and tapered as it traveled laterally. Of note, dissolved in sterile saline without preservative and the in all specimens, the bulk of the corrugator muscle injection volume is small. belly was at or slightly above the plane of a transverse Response to botulinum toxin injection in the gla- line drawn through the mideyebrow (Figure 6). In the bella does not appear to be prevented by patient im- male specimens, 13 were even with this transverse line, mune defense mechanisms. Antibodies to botulinum toxin while 11 were above it. In the female specimens, 10 type A have been described in patients receiving large were even with and 16 were above the transverse plane doses for long periods,23 but the smaller doses used in of the mideyebrow. this region have not resulted in antibody production with The procerus was fairly consistent in thickness (Յ1 similar procedures. Rather, the occasional lack of re- mm) throughout its course. The depth ranged from 1 to sponse to botulinum toxin injection may be caused by 4 mm, with an average of 2.8 mm and 2.5 mm in male placement error.17,18,20,24 In these cases, injection or mi- and female specimens, respectively. While this differ- gration of the toxin into the postseptal space of the orbit ence was not statistically significant, the difference in is also possible, with resultant complications. In the length was: the average length for females was 19.1 mm present study, surface landmarks that were relevant to compared with 16.4 mm for males (PϽ.01). the involved musculature, but remain consistent and eas- The frontalis muscle had a uniform depth, with no ily identifiable from specimen to specimen, were cho- significant difference between measurements at the vari- sen for evaluation. Hence, the lateral canthus, midpu- ous locations within each specimen. However, the depth pillary line, medial canthus, and midline were selected. range among specimens was 2 to 7 mm. The lateral canthal region served as a baseline measurement for the corrugator supercilii since this muscle was COMMENT not expected to be present at this location. The corrugator turns sharply toward its insertion in the skin in the Since glabellar rhytids are largely functional, effective man- region of the midbrow; however, since the midpupillary agement must address the cause rather than simply the line is medial to this point, the corrugator muscle was effect. In doing so, complications related to lid or brow still present at this landmark in all but 1 specimen. This ptosis must be avoided. As a result, surgical approaches, is not always apparent in the usual anatomical depic- whether transpalpebral or through a forehead or brow tions of the area. The clinical significance of this finding

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Muscle Finding Application Corrugator Vertical rhytids supercilii Insertion: at or medial to Treatment directed medial midbrow to this landmark Origin: junction of frontal Treatment directed lateral and nasal bones to this region (ie, does not extend to midline) Bulkiest portion at medial Treatment focus brow with significant Figure 9. The use of accurate anatomical landmarks should produce component at consistent results. For vertical glabellar rhytids, botulinum toxin type A midpupillary line should be injected into the thickest portion of the corrugator supercilii Muscle belly at or above Direct treatment at or muscle adjacent to the medial aspect of the brow and even with or above the horizontal plane above this plane to horizontal plane passing through the eyebrow (large arrow). To eliminate through eyebrow avoid ptosis horizontal rhytids in the glabellar region, the procerus should be injected in Procerus Horizontal rhytids the midline, slightly caudal to the root of the nose (small arrow) (illustration Thin, narrow, depth of Treatment directed at courtesy of Christine Gralapp, CMI, MA). 1-4 mm midline, adjacent to skin Longer in women than More attention must be landmarks may serve as further guidelines, with occa- men given to procerus sional modification dictated by clinical judgment. Al- muscle in women though an EMG neuromuscular stimulator attached to an EMG needle or a gated muscle detector can be used to identify the most active part of the muscle pre- is that this muscle can largely be ignored beyond the mid- cisely,18,19 many clinicians have not found this to be nec- brow but requires attention at the midpupillary line where essary.17,24,25 The use of accurate anatomical landmarks significant muscle bulk remains. should produce confident, consistent results. Figure 9 While the insertion of the corrugator supercilii demonstrates appropriate injection sites based on these was variable, the origin was relatively consistent at the landmarks. Specifically, for vertical glabellar rhytids, in- junction of the frontal and nasal bones, near the supero- jections should be into the thickest portion of the cor- medial orbital rim. The contracted corrugator can often rugator supercilii muscle adjacent to the medial aspect be felt between the examiner’s finger and thumb, as well of the brow and even with or above the horizontal plane as seen as a bulge in the region of the medial aspect of passing through the eyebrow. For horizontal rhytids, the the brow. This is consistent with our finding that the procerus should be injected in the midline, slightly cau- bulkiest portion of this muscle belly lies here. Many dal to the root of the nose. The selection of sites must, anatomical drawings depict a vertical component to of course, be influenced by clinical judgment during ac- the corrugator medially. Our dissections did not sub- tivation of the involved muscles with or without an EMG stantiate this. Similarly, although some authors sug- stimulator. gest existence of a depressor supercilii in this region,2 The findings of this study give detailed anatomical this muscle was not identified as a distinct entity in support for improved methods of treating rhytids in the our specimens. glabellar region. They also stimulate a number of ques- Evaluation of the horizontal position of the corru- tions for future investigation: With more accurate place- gator yielded interesting results. The bulk of the muscle ment, can the therapeutic dosage of botulinum toxin be belly was invariably at or above the plane of a transverse reduced? Should the botulinum toxin be injected along line drawn coronally through the middle of the eye- the length of the muscle or tangentially in the muscle belly brow. This information is useful in avoiding posttreat- only? Can ptosis be avoided, with continued clinical suc- ment ptosis with botulinum toxin injections. The needle cess, by orienting the injection needle superolaterally in should be directed at or slightly above this midbrow plane the region of the medial brow? to achieve maximum effect while avoiding injection or migration of toxin through the orbital septum. CONCLUSIONS The procerus muscle is thin and narrow. However, its relatively consistent depth (1-4 mm) and midline lo- Surgical removal of the corrugator and procerus muscles cation make it an easy target. The finding that the pro- is the ultimate treatment for functional glabellar frown cerus was significantly longer in women than men was lines. However, whether through a transpalpebral or fore- unexpected. This may explain our clinical observation head-brow approach, this represents a major operation, that women, more than men, complain of transverse which may not be appealing to patients for manage- rhytids at the nasal base. ment of glabellar frown lines alone. The most attractive The summary of anatomical findings in the Table noninvasive, transcutaneous management now appears may be applied to any approach for management of rhytids to be by means of the intramuscular injection of botuli- in this region, but it is particularly relevant to blind, trans- num toxin type A. Achieving effective results, while mini- cutaneous injection of botulinum toxin type A. Activa- mizing recurrence or attendant complications, depends tion of the involved muscles by frowning aids in the gen- on accurate understanding of the muscular anatomy and eral localization, but once this is established, surface associated surface landmarks.

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