Pertinent Muscular Anatomy and Physiology
Gary D. Monheit, M.D.
Associate Professor
Department of Dermatology
University of Alabama at Birmingham
Birmingham, Alabama

For Horizontal Forehead Lines:

Horizontal forehead lines are primarily caused by the action of the frontalis muscle. This muscle, lying just below the subcutaneous tissue, is a vertically oriented muscle that is continuous with the galea aponeurotica superiorly and interdigitates with the procerus, orbicularis oculi, corrugator supercilli, depressor supercilli, and the skin of the eyebrow inferiorly. Frontalis contraction causes brow elevation. The temporal branch of the facial nerve is responsible for the action of this muscle with denervation resulting in brow ptosis and loss of forehead motion. The width of this muscle can be noted clinically by the extent of the forehead crease.

For Brow Lift:

Brow depression can be perceived as an angry or scowling expression. The brow depressor muscles include the corrugator supercilii, procerus, and the supramedial and supralateral portions of the orbicularis oculi. These three muscles work together to close the eyes and squint creating transverse and oblique glabellar lines. The corregator supercilli muscle is a paired muscle originating at the medial end of the superciliary arch and inserting into the frontalis and skin of the brow. It acts via the temporal nerve to pull the brow together and downward causing vertical glabellar frown lines. The procerus muscle, innervated by the zygomatic branch of the facial nerve, attaches to the nasal root skin primarily acting to shorten the nose causing “rabbit lines” by drawing the forehead skin and eyebrows inferiorly. The orbicularis oculi muscle is divided into orbital and palpebral portions. It inserts into the medial palpebral ligament and circumferentially surrounds the eye. The superior portion of the orbicularis oculi is innervated by the temporal nerve. The orbital component allows tight closure of the eye while the palpebral portion allows gentle eye closure.

For references:

1. Bolognia, Jorizzo, Rapini et al. Dermatology (It’s the new big derm text)
2. Clemente. Anatomy. A regional Atlas of the Human Body. 4th ed. Williams and Wilkins1997.

2. Tx sites and dosage - site studies

Evaluation of individuals for symmetry, brow ptosis, and underlying musculature is crucial when treating forehead rhytides and lifting the brow. If asymmetry is present, it should be brought to the attention of the patient. Photographs not only help to track objective changes with treatment but also help to remind the patient of their progress or prior asymmetries. In order to decrease the incidence of brow ptosis it is important to identify those patients who compensate for brow ptosis by recruiting the use of the frontalis muscle to subconsciously lift their brows to a natural level. In those patients who recruit the frontalis muscle to prevent brow ptosis, injection of low dose BOTOX approximately 2.5 cm above the brow lessens this potential side effect.(Goodman G: Botolinum toxin for the correction of hyperkinetic facial lines. Aust J Dermatol 39:158-163, 1998 and Carruthers and Carruthers; Seminars in Cutaneous med and surg. Botulinum Toxin Type A: History and Current Cosmetic Use in the Upper Face) Brow elevation occurs by contraction of the frontalis and/or relaxation of the brow depressor muscles. The goal of treatment of the forehead rhytides is to soften these lines without causing brow ptosis or complete loss of facial expression. There have been several studies done to determine optimal dosage and treatment sites.

Carruthers et al describes a well accepted method of injection of 10 to 20 U BTX-A, diluted 100U Botox with 1 ml sterile saline, distributed in 4-5 injection sites horizontally across the midbrow 2-3 cm above the eyebrows. Four injection sites are used if the brow is less that 12 cm and 5 for greater that 12 cm. (1. Carruthers and Carruthers; Seminars in Cutaneous med and surg. Botulinum Toxin Type A: History and Current Cosmetic Use in the Upper Face). The Carruthers believe that the brow depressors should be treated at the same time as the frontalis to aid in the prevention of brow ptosis. Even with this cautious approach, a minor degree of brow ptosis or swelling of the upper eyelids is seen in a few patients. In a prospective, double-blind, randomized, parallel-group, dose-ranging study of BOTOX in females with horizontal forehead rhytides, Carruthers et al also observed that higher BOTOX A doses resulted in greater efficacy and longer duration of effect in the reduction of horizontal rhytides when injections of 16, 32, or 48 units of BOTOX A into the brow elevators and depressors. There was a higher incidence of brow ptosis seen in the 32-U and 48-U groups, 21% and 10% respectively than seen in the 16-U group, 0%. (Dermatology Surgery 2003 May 29(5) 461-7)

Keen et al conducted one of the first double-blind placebo-controlled studies of BTX-A use in facial wrinkles. In this study, 11 subjects were treated including 9 for forehead lines and 2 for periorbital wrinkles, the toxin was diluted to a concentration of 2.5 or 5 IU/ml and electromyography was utilized to find the most active portion of the muscle injected. Forehead injections included 8 injection sites totaling 10U of BTX-A on one hemiforehead with normal saline injected on the opposite side of the forehead. Injections into the periorbital wrinkles with 5-U of Botox in two separate sites was done on 2 subjects with normal saline injection on the opposite side. Specific injection sites were not noted. The patients were both self evaluated and evaluated by a physician on a scale from 0 to 3, with 0 reflecting no facial wrinkles and 3 reflecting severe facial wrinkling. Both the forehead and periorbital scores were averaged together. At repose, a mean reduction in wrinkles of 1.3 rating points was seen by the patients while the physicians rated the mean reduction to be 1.5. When the subjects were asked to contract the injected muscles, a mean reduction of 2.0 and 1.5 were seen by the subjects and physicians respectively. Two of the 11 patients in this study felt that their eyebrow had dropped slightly while 3 or 11 thought the injection was painful. One reported a changed in the shape of her brow. There were no physician comments noted about the above changes. (Keen M, Blitzer A, Aviv J et al. Botulinum toxin A for hyperkinetic facial lines: results of a double-blind placebo-controlled study. Plast Reconstr Surg 1994:94:94-9)

In a study conducted by Goodman, 1-2 U of Botox was injected into the ridges created between the forehead lines when the subjects were asked to raise their eyebrows. All injections were made at least 2 finger-breadths above the brow. A concentration of 10 U/ml was used and 1 to 2 units were injected into 2 sites on each ridge. Two of his four patients had complete elimination of their forehead lines with none having brow ptosis. The most common complications included bruising and minor discomfort with injection. (Goodman G, Australas J Dermatol. 1998 Aug; 39(3):158-63)

Another study conducted by Guerrissi and Sarkissian used 12-20 U BTX-A in a 25 U/ml dilution. A pattern of injection was used based on the number of rhytides and lateral extension of the frontalis muscle, however all sites injected were 2.5 cm above the brow. Of the 17 patients in the study, all were satisfied with the results, however, 2 patients developed eyebrow palsy that lasted for 55 to 70 days, 2 patients developed a skin rash (not elaborated on in the article) and edema, and 1 patient developed ecchymosis. (Guerissi J, Sarkissian P. Local injection into mimetic muscles of Botulinum toxin A for the treatement of facial lines. Ann Plast Surg. 1997 Nov; 39(5):447-53)

It is difficult to compare each of these studies due to variability of concentration of Botox used, number of units injected per site, site injection variability, patient population, and lack of specific documentation of injection sites however, most studies agree with the use of 10-20 U of Botox approximately 2 cm above the eyebrow to prevent ptosis of the brow. In our clinic, patients are treated with a total of 10-30 U BTA-A diluted 100 U in 1 ml normal saline in 4-5 injection sites 1-3 U across the midbrow about 2 cm above the eyebrows. A second row of injections of 1-3 U is then placed approximately 1 cm above this. Women are treated with fewer units of botox in the lateral forehead position if lateral elevation of the eyebrow or a more open central face is desired. Men are typically treated with the same number of units across the brow in two rows as above with care paid to lateral injection so that they will not have an elevated lateral brow. Typically men have a more developed musculature, so they receive more units of botox than women. We agree with Carruthers et al and typically inject the brow depressors when treating horizontal rhytides. Our percentage of eyebrow ptosis is approximately 2%.

Decreased activity of the brow depressor muscles can lift the brow and alleviate a scowling or angry expression caused by overactivity of these muscles. It is important to remember that the inferior portion of the frontalis interdigitates with the corrugator supercilii, procerus, and the medial portion of the orbicularis oculi. Clinical observation of the skin lines overlying these muscles is a result of the equilibration of the individual opposing muscular forces developed due to facial expression. Injecting into the areas of muscular overlap can affect each of the underlying muscles, however the bulk of the frontalis lies above this area of overlap. Injecting into the middle of the muscle bellies of the brow depressor muscles or the upper and middle frontalis leads to the most consistent results of brow elevation without ptosis.

In 1998, Frankel et al injected the corrugators and procerus with a total of 20 U of BOTOX-A to determine if the medial brow could be elevated. Of the 30 patients in the study, subjective comparison found 62% to have a mean increase in height of the medial brow of 10% above baseline and a 48% to have a mean increase in height of the midpupillary brow of 14% above baseline after treatment. In 59% of the patients, a measurement of the interbrow distance also showed an increase. In this study however, no side effects of treatment were mentioned and no statistically significant analysis was preformed. (Frankel AS, Kamer FM, Chemical Browlift. Arch Otolaryngol HeadNeck Surg. 1998 Mar; 124(3):321-3)

In 1999, Huilgol et al injected the glabellar area with 7-10 U Botox and the supralateral eyebrow with 0-2.5 U of BOTOX-A bilaterally, to a total dose of 10-14U. Five of the seven women in the study showed brow elevation of 1-3 mm with a mean elevation of 1 mm. Two of the individuals showed no change. There were no significant adverse effects. (Huilgol SC, Carruthers A, Carruthers JD. Raising eyebrows with botulinum toxin. Dermatol Surg. 1999 May;25(5):373-5)

Huang et al evaluated 11 women for alteration in brow position after BOTOX-A treatment of the brow depressor muscles. In this study the concentration of botulinum toxin used was 5 U/0.1 ml (2 ml normal saline in a 100 U vial). Is this correct??? It seems like the concentration would be .5/0.1 ml. Botulinum toxin injections were placed intramuscularly along both orbital rims with four equally spaced sites beginning from the midpupillary line and extending horizontal to the lateral canthus. Each site received 2.5 U of the toxin, for a total of 10U per eyebrow. Five units were injected into the corrugator muscle at each medial brow bilaterally with the injection needle aimed in an upward and horizontal direction. Brow position was then measured at relaxed and elevated positions from the pupil to the nasal, central and temporal brow. Elevation of the brow occurred in both the relaxed and elevated positions with the largest elevation taking place in the central brow region. The largest mean elevations were noted in the right central brow position (relaxed 1.86mm, elevated 2.09 mm) and the left central brow position (relaxed 3.06 mm, elevated 2.86 mm). No adverse effects such as ptosis, bruising, or hematoma were noted in this study. However, in this study, a few patients had negative changes in the brow distance. These changes were not severe enough to be classified as clinical ptosis and were thought to be attributed to diffusion of the toxin into the frontalis muscle. (Huang W et al. Browlift with Botox. Dermatol Surg. 2000 Jan;26(1):55-60)

Ahn et al injected the lateral orbicularis oculi bilaterally with 7-10 U of Botox to measure the efficacy of botox injection for a temporal brow lift. They found an average brow elevation from the midpupil was 1.02 mm and the average brow elevation from the lateral canthus was 4.83 mm when evaluated at 2 weeks after treatment. (Ahn MS et al. Temporal brow lift using botox A. Plast Reconstr Surg. 2000 Mar;105(3):1129-35.

Upon reviewing the literature, there are multiple proven studies to lift the brow. Injection into individual brow depressor muscles alone or several brow depressor muscles can lead to lifting of the brow and the technique used should be based upon the effect needed by the patient. The goal with treatment of the brow depressors with botox is complete or near complete paralysis of these muscles as these muscles aid only in frowning and are not necessary for other important activity. In our clinic, we begin by injecting 3-7 U/side into the corrugator with the needle aimed in a superior fashion and 3-7 units/side approximately 1 cm above this. We then inject the procerus just below the level of the brow centrally with 5-10 U. The procerus is then gently massaged in a horizontal fashion to aid in the diffusion of botox to the depressor supercilli. 3-7 U Botox is injected just inferior to the lateral brow as well as 1 cm above the brow at the pupillary line. We honor the area of the midbrow as to not create an eyelid ptosis. This injection method not only lifts the brow, but it also treats glabellar lines and can lead to the perception of a more open central face. Our percentage of eyebrow and brow ptosis is approximately___________________.

3. Complications:
Adverse reactions associated with Botox A include antibody resistance, idiosyncratic flu like symptoms, distant electromyographic changes, dry mouth, brow and lid ptosis, pain, localized reactions including urticaria, erythema, and edema, ecchymosis, headache, and short-term hypesthesia. (Sadick. Complicaitons of Cosmetic Surgery; Yearbook of Dermatology and Dermatologic Surgery 2002. p 19-41) The most significant complication of treatment of the frontalis is brow ptosis. Each patient’s Botox treatment should be individually based on their underlying anatomical musculature and inherent propensity to elevate their brow to prevent ptosis. Treatment of the brow depressors may be necessary after brow ptosis has occurred. To prevent brow ptosis, a cautious approach to the lower frontalis should be used with injections staying approximately 2 cm above the brow. Injections should be made directly into the muscle is a controlled manner with Botox that has been appropriately diluted. The areas in general should not be massaged. Patients should be instructed to stay upright for 3-4 hours and not to manipulate the area that has been injected. We also recommend that the patients contract their musculature for 1-3 hours after treatement. Injecting the glabella and entire forehead can increase the chance of ptosis. (Klein. Complications and Adverse Reactions with the use of Botox. Seminars in Cutaneous Med and Surg, Vol 20, No2 (June), 2001: pp 109-120)

The most common complication in treatment of the glabellar complex is ptosis of the upper eyelid secondary to the diffusion of Botox through the orbital septum where it can affect the upper eyelid levator muscle. It occurs between a 24 hour to 10 day period and can persist up to four weeks. Eyelid ptosis can be treated by alpha adrenergic agonists eyedrops, Iopidine 0.5% and/or Neosynephrine hydrochloride 2.5%. Neosynephrine acts via Muller’s muscle which is a smooth muscle located beneath the levator muscle of the upper eyelid. To avoid eyelid ptosis, treat conservatively in those patients who may have a reduced orbital septum such as the elderly. Treat accurately with low volumes of Botox. Injection above the midpupillary line should be at least 1 cm above the supraorbital rim. (Klein. Complicaitons and Adverse Reactions with the use of Botox. Seminars in Cutaneous Med and Surg, Vol 20, No2 (June), 2001: pp 109-120)

There is evidence that patients undergoing cosmetic treatment with Botox can produce circulating neutralizing immunoglobin G anitbotulinum toxin A antibodies. This is much more common in patients being treated for neurologic conditions thus requiring larger amounts of the toxin to be injected. The factors causing antibodies to develop are unknown. (Matarasso SL: Complications of Botulinum A exotoxin for hyperfunctional lines. Dermatol Surg 24:1249-1254, 1998.)

Idiosyncratic flu like symptoms are most likely secondary to the proteins in the Botox mixture as opposed to the Botox itself and likely are a mild type of serum sickness. Techniques such as distraction, concurrent muscle stimulation, or application of ice can be used to reduce the pain of the local injection. Localized reactions such as urticaria, edema, and erythema have been reported and are a nonsystemic form of hypersensitivity likely related to local histamine and cytokine release. Bruising can be minimized by avoidance of NSAIDs, aspirin products as well as other anticoagulants. There have been sporadic reports of headache occurring after Botox injection, but more commonly, chronic tension and migraine headaches are improved after the injection. If headache occurs, OTC analgesics may be used. Short-term hyperesthesia is a rare portinjection sequela which remits spontaneously in 48-72 hours. (Klein. Complicaitons and Adverse Reactions with the use of Botox. Seminars in Cutaneous Med and Surg, Vol 20, No2 (June), 2001: pp 109-120)

Patients must be aware of the decreased facial expressivity and the potential change in the brow shape and position when the frontalis and brow depressors are tx with Botox. Multiple small doses injected at 1-2 cm intervals across the forehead will help to weaken, rather than paralyze the frontalis letting facial expression occur while rhytides are treated. Careful placement of the Botox to shape the brow in a pleasing fashion should be done. The dosage is dependent upon the individual but usually ranges from 10-40 U for the brow lift and forehead treatment. The quizzical brow occurs when injection of botox into the lateral fibers of the frontalis is neglected causing weakening of the central forehead without weakening of the lateral forehead. This can be corrected by injecting 1-5 U of Botox laterally.
Contraindications to the use of botulinum toxin include pregnancy, nursing, and pre-existing neuromuscular condition. Medication such as aminoglycosides, penicillamine, quinine, and calcium channel blockers can potentiate the effects of BOTOX and should not be used concomitantly.