Anatomy of the Corrugator Supercilii Muscle

Home , Frontalis muscle, Orbicularis oculi muscle

ORIGINAL ARTICLE Anatomy of the Corrugator Supercilii Muscle

Jung I. Park, MD, PhD; Todd M. Hoagland, PhD; Min S. Park, MD

Objective: To define the anatomy of the corrugator Results: The origin of the CSM has a wide base, span- supercilii muscle (CSM). ning across 0.6 cm from the midline and the supraorbital notch/foramen. The area of the muscle origin mea- Design: Cadaver dissections following a preset approach. sured 0.98ϫ2.52 cm on the right side and 1.04ϫ2.35 cm on the left side. The lateral extent of the CSM inser- Setting: Anatomy laboratory at a medical school. tion measured 4.27 and 4.50 cm from the midline on the right and left sides, respectively. Method: Sixteen sides of 8 preserved cadaver heads were dissected. Inferiorly based trapdoor-type flaps were de- Conclusions: The CSM originates as 3 or 4 thin, rect- veloped in the subgaleal plane. The bone origins of the angular, panellike muscle groups occupying a wide area CSM were first identified. The muscles were then fol- across 0.6 cm from the midline and the supraorbital notch/ lowed to their insertions. The origin and outline of the foramen. The muscle groups travel parallel to one an- muscles were plotted on the face of the cadaver. Follow- other in an oblique course without distinguishable ob- ing the measurements, we transferred the configuration lique or transverse components. of the CSM to the image of a computer-manipulated face of a model. Arch Facial Plast Surg. 2003;5:412-415

NTRODUCTION OF the endo- the middle and the lateral third of the eye- scopic forehead lift procedure brow. These findings contrast with all pre- has heightened interest in the vious attempts to describe the CSM. anatomy of the corrugator supercilii muscle (CSM). Unlike the METHODS Icoronal or pretrichial approach, the ex- Cadaver dissections were carried out at the posure of the muscle is compromised in anatomy laboratory of the Northwest Center the endoscopic approach. The lack of sat- for Medical Education, Indiana University isfactory improvement of glabellar frown- School of Medicine, Munster. First, 4 cadav- ing following the endoscopic procedure ers were dissected during August through Oc- has been attributed to inadequate resec- tober 2000. Then, 4 more cadavers were dis- tion of the CSM. The recent use of botu- sected during August through November 2001. linum toxin type A to treat frowning also The CSMs were dissected on 8 cadavers, to- taling 16 sides. There were 4 male and 4 fe- demands a better understanding of the male cadavers. Reference points were identi- anatomy of the CSM. fied and marked on the cadaver faces to indicate From the Department of Descriptions of the CSM in text- the locations of the medial canthus, the supra- Surgery (Dr J. I. Park), books and in the literature are scant, in- orbital notch/foramen, and the lateral can- Northwest Center for Medical complete, and often incorrect. Hollins- thus. Vertical lines were drawn through the Education, Department of head1 described the CSM as “a small, midline, the medial canthus, the supraorbital Anatomy (Dr Hoagland), and deeply situated muscle arising from the notch/foramen, and the lateral canthus bilat- Indiana University School of frontal bone above the rim of the orbit close erally. Next, horizontal lines were drawn Medicine (Dr M. S. Park), to the nasofrontal suture and extending lat- through the medial canthus, supraorbital notch/ Munster. Dr Hoagland is now erally and upward to insert into the skin foramen, and 2 and 3 cm above the supraor- with Boston University School bital notch/foramen. These last lines were ar- of Medicine, Boston, Mass; of the medial half of the eyebrow.” In the bitrarily chosen after the pilot dissection to Dr M. S. Park is now with the present study, we describe the anatomy of contain the upper fibers of the CSM (Figure 1 University of California, the CSM based on cadaver dissections. The and Figure 2). San Diego Medical Center, CSM was found to have a larger mass, a An inferiorly based trapdoor-type flap was San Diego. broader bone origin, and an insertion on then developed through the horizontal 3-cm

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2 cm

SOH

MCH

M MC SO

Figure 1. Horizontal and vertical lines crossing reference points: midline, medial canthus, supraorbital notch/foramen, and 2 and 3 cm above the supraorbital notch/foramen.

line, the vertical midline, and the vertical line crossing the lateral canthus (Figure 3). The flap was elevated from the peri- osteum. As the dissection approached the supraorbital rim, the bone origin of the CSM became visible. The dissection then pro- Figure 2. A, Photograph of the computer-manipulated face of a model. gressed superficially, following the fibers of the CSM up to where B, A view of the corrugated supercilii muscle (CSM) based on the the muscle ended in the subcutaneous tissue or interdigitated measurement of the CSM from the reference points and lines. M indicates with the frontalis muscle. The pattern of interdigitation with midline; MC, medial canthal vertical line; SO, supraorbital vertical line; the orbicularis oculi muscle was not actively sought via this ap- SOH, supraorbital horizontal line; and MCH, medial canthal horizontal line. proach. Through this approach, the CSM should be removed prior to exposure of the orbicularis oculi muscle. In an attempt to detemine the pattern of interdigitation between the CSM and the orbicularis oculi muscle, without vio- lating the anatomy of the CSM, we elevated the skin and the subcutaneous tissues. The interdigitation pattern was not as clearly defined as that of the frontalis and corrugator muscles. The difficulty encountered was caused by the presence of dense fibrofatty tissue under the eyebrows, which compromised clean dissection in the area of the interdigitation between the CSM and the orbicularis oculi muscle. Once the CSM was fully dissected but prior to skin eleva- tion, needles were inserted through the skin to mark the boundary of the CSM on the surface of the face (Figure 4). The needle penetration points were then marked with a marking pen. Next, these points were connected to draw the boundary of the CSM on the forehead and eyebrow (Figure 5). The location of the 4 corners of the CSM were measured as distances from the reference points and lines. A photograph of a model face was ob- Figure 3. An inferiorly based trapdoor-type flap was developed through the horizontal line 3 cm above the supraorbital notch/foramen, the midline, and tained and altered by computer manipulation to match the av- the vertical line through the lateral canthus. eraged face proportions of the cadavers. The outline of the CSM based on the measurements and the 3-dimensional configuration of the CSM was then applied to the altered model face by on the left. The vertical height of the base measured 0.98 computer reconstruction (Figure 2). cm on the right side and 1.04 cm on the left side. The origin of the CSM is compartmentalized into 3 RESULTS or 4 vertically oriented, long, narrow, rectangular areas. The muscle groups arise from each compartment as a thin, The average distance between the medial canthal hori- rectangular, panellike sheet of muscle and then travel par- zontal line and the supraorbital horizontal line was 1.55 allel to each other in a lateral and superior oblique course cm. From the midline to the medial canthal vertical line (Figure 6). In our cadavers, there were no distinguish- the distance was 1.82 cm on both sides. The distance be- able transverse and oblique components of the CSM. tween the midline and the supraorbital vertical line was Beyond the supraorbital notch/foramen, each muscle 2.92 cm on the right and 2.95 cm on the left. group inserts into the skin. The more medial groups at- The CSM arises from the supraorbital ridge of the fron- tach first followed by the lateral groups, with insertions tal bone. The origin has a wide base, spanning across 0.6 progressing laterally thereafter. At the insertion area, the cm from the midline and the supraorbital notch/foramen. muscle fibers blend into each other and lose their com- The average width of the base of the muscle origin in our partmental characteristics. The boundary of the CSM is cadavers measured 2.52 cm on the right side and 2.35 cm defined in terms of distances from the reference points and

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©2003 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 Figure 4. Needles are inserted through the skin to mark the boundary of the corrugated supercilii muscle on the surface of the face.

Figure 5. Surface representation of the corrugated supercilii muscle obtained through the needle-insertion method.

lines, as summarized in Table 1 and Table 2. The average lateral extent of the CSM measured from the midline was 4.27 cm on the right side and 4.55 cm on the left. Superiorly and laterally, the CSM fibers interdigitated with the fibers of the frontalis muscle. Interdigita- tion with the orbicularis oculi muscle was not clearly dem- onstrated. Although the CSM is distinctively under the frontalis muscle, medial to the supraorbital notch/ foramen, the CSM shares the same plane as the frontalis and the orbicularis muscle at its lateral skin insertion.

COMMENT Figure 6. The corrugated supercilii muscle is compartmentalized into 3 or 4 1 thin, rectangular, panellike sheets of muscle. The muscle groups travel in Hollinshead describes the CSM as a small muscle aris- parallel, running obliquely in a lateral and superior direction. ing from the frontal bone close to the nasofrontal suture. The illustrations found in other publications also depict the bone origin as being confined to a small in parallel in an oblique course with a distinctive loose area.2,3 Contrary to these publications, we found that the areolar space between each group of muscle. Previously bone origin occupies a large area of approximately 1ϫ2.5 described oblique and transverse patterns of the CSM were cm spanning almost the entire area from the midline to not found.3 The deep galeal plane covering the inner as- the supraorbital notch/foramen. And instead of the area pect of the frontalis muscle appears to become investing being circular in shape, the CSM is rectangular in shape. fascia for the CSM. We were unable to find any previous descriptions The supraorbital neurovascular bundle runs poste- of the compartmentalization of the CSM muscle groups rior to the CSM as noted in previous documentation. How- at the site of origin. These panellike muscle groups travel ever, 1 fiber always penetrates the CSM about 1 to 2 cm

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©2003 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/26/2021 Table 1. Distances From the Reference Lines Table 2. Distances From the Reference Lines to the Medial 2 Corners of the CSM* to the Lateral 2 Corners of the CSM*

Right Left Right Left

Medial Aspect M MCH M MCH Lateral Aspect SO SOH SO SOH Upper 0.67 2.00 0.67 2.09 Upper 1.35 1.92 1.60 2.07 Lower 0.60 1.02 0.60 0.95 Lower 1.95 0.47 2.25 0.50

Abbreviations: CSM, corrugator supercilii muscle; M, midline; Abbreviations: CSM, corrugator supercilii muscle; SO, supraorbital vertical MCH, medial canthal horizontal line. line; SOH, supraorbital horizontal line. *Data are centimeters. *Data are centimeters.

above the supraorbital notch/foramen. The lateralmost muscle). To clarify the interdigitation pattern between group of the CSM origin is located just medial to the su- the CSM and the orbicularis oculi muscle, we per- praorbital notch/foramen. formed the dissection from the skin by peeling off the We found the supraorbital notch/foramen to be 27 skin from the area of the orbicularis oculi muscle. The to 33 mm from the midline, comparable with previous orbicularis oculi muscle has a distinctive circular pat- studies.4,5 Beyond the supraorbital notch/foramen, the tern, as expected, and was located inferior to the CSM. CSM groups begin to merge gradually before their in- However, the interdigitation pattern was not clearly dem- sertion into the subcutaneous tissue. Interdigitation with onstrated on our dissections. the frontalis muscle occurs among the uppermost fi- Four main conclusions may be drawn from our bers. The interdigitations appear to be a gradual union study: (1) The CSM originates as 3 or 4 thin, rectangu- of 2 muscle fibers that transition from the oblique direc- lar, panellike muscle groups. (2) Its bone origin has a wide tion of the CSM to the vertical one of the frontalis muscle base spanning across 0.6 cm from the midline and su- rather than a true interwoven pattern. praorbital notch/foramen. (3) The muscle groups travel Lateral extensions of the CSM are somewhat poorly an oblique parallel course; there is no distinguishable ob- defined owing to this gradual union of 2 muscles. How- lique or transverse component. And (4) the CSM has a ever, distinctive fibers of the CSM extend laterally up to larger mass and a wider base than previously described. 4.55 cm from the midline, in contrast to previous descriptions of the CSM being confined to the medial third Accepted for publication April 3, 2003. of the eyebrow.1,6 Our dissection revealed that the CSM We thank Saveen Kondamuri, MD, for his assistance extends even to the lateral third of the eyebrow. An ex- in reviewing the manuscript. planation for this discrepancy might be that, in previ- Corresponding author: Jung I. Park, MD, PhD, 9305 ous dissections, the lateral portion of the CSM was con- Calument Ave, Suite A-2, Munster, IN 46321 (e-mail: sidered to be part of the frontalis muscle or orbicularis [email protected]). oculi muscle. This confusion may have occurred be- cause the earlier dissections were performed from the sur- REFERENCES face, unlike our deep-to-surface dissection during which the CSM was clearly defined first, and then the muscle 1. Hollinshead WH. The Head and Neck. 2nd ed. New York, NY: Harper & Row; 1968: was followed laterally and superficially without a loss of 339. Hollinshead WH, ed. Anatomy for Surgeons; vol 1. fiber orientation. 2. Williams PL, ed. Gray’s Anatomy. 38th ed. Philadelphia, Pa: WB Saunders Co; A similar example may be found in the dissection 1985:792. of the peripheral branch of the nerve, which we found 3. Knize DM. The Forehead and Temporal Fossa. Philadelphia, Pa: Lippincott Wil- liams & Wilkins; 2001:5, 12-13. to be significantly easier and more complete when the 4. Webster RC, Gaunt JM, Hamdan US, Fuleihan NS, Giandello PR, Smith RC. Su- nerve was dissected from the main trunk to the periph- praorbital and supratrochlear notches and foramina: anatomical variations and ery as opposed to attempting nerve exploration at the dis- surgical relevance. Laryngoscope. 1986;96:311-315. tal fine nerve fiber first. When the dissection is ap- 5. Miller TA, Rudkin G, Honig M, Elabi M, Adams J. Lateral subcutaneous brow lift and interbrow muscle resection: clinical experience and anatomic studies. Plast proached from the surface, the delicate muscle fibers with Reconstr Surg. 2000;105:1120-1127. similar fiber orientation can be mistaken as a part of an- 6. Lemke BN, Stasior OG. The anatomy of eyebrow ptosis. Arch Ophthalmol. 1982; other muscle (ie, the CSM as a part of the orbicularis oculi 100:981-986.

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