Underlying the forehead is the frontal bone. Laterally, the frontal bone is crossed by a curved ridge called the temporal crest (temporal ridge or temporal fusion line). This palpable landmark separates the forehead from the temporal fossa laterally (FIG 1). The temporalis muscle takes its origin from the temporal fossa.

The surgical significance of the temporal crest line is that overlying fascial layers are tethered to bone in a band immediately medial to the palpable ridge. This has been called the zone of fixation or the zone of adhesion.^2,3 Inferiorly, where the ridge approaches the orbital rim, the fixation becomes broader and denser, forming the orbital ligament, also known as the temporal ligamentous adhesion. Regardless of the surgical technique used, when a full-thickness forehead flap is mobilized, all fascial attachments to bone must be released, including the zone of adhesion and the orbital ligament, plus attachments to the supraorbital rim and lateral orbital rim.⁴

The temporal crest also marks a change in nomenclature as tissue planes transition from lateral to medial. The deep temporal fascia covers the temporalis muscle and is attached to bone along the temporal crest. It then continues medially as the periosteum of the frontal bone. Similarly, the superficial temporal fascia (also known as the temporal-parietal fascia) continues medially as the galea aponeurotica.

The galea aponeurotica splits into a superficial and a deep layer to encompass the frontalis muscle. Inferiorly, the deep galea layer separates further into three separate layers: two layers encompass the galeal fat pad, and a third layer is adherent to periosteum.² Superficial to the deepest galeal
layer is the so-called glide plane space, which allows the scalp flap to shift superiorly.

The galeal fat pad extends across the entire width of the lower 2 cm of the forehead; medially it encompasses the supratrochlear nerves and much of the corrugator musculature. The galeal fat pad is separated from the preseptal fat (retro-orbicularis oculi fat or ROOF) by one of the layers of galea (see above). Laterally, this galeal layer is thought to be inconsistent, with some individuals having continuity between the galeal fat pad and the preseptal fat (ROOF). Within the eyelid, the septum orbitale divides the preseptal fat (ROOF) from orbital fat.

Muscle anatomy plays a significant role in determining eyebrow shape and position. In addition to the soft tissue attachments, the level of the eyebrow is the result of a balance between the muscular forces that elevate the brow, the muscular forces that depress the brow, and gravity.

Brow depressors in the glabella originate from bone and insert into soft tissue. The procerus runs vertically near the midline, the depressor supercilii and supramedial orbicularis run obliquely, and the corrugator supercilii runs mostly transversely.

The transverse corrugator supercilii is the largest and most significant of these muscles. Useful landmarks to locate the corrugator are as follows: the corrugator originates from the orbital rim at its most superomedial corner, right at the entrance to the orbit. The transverse head passes through galeal fat becoming more superficial until it interdigitates with the orbicularis and frontalis under a skin dimple that is visible when the patient frowns.

The orbicularis encircles the orbit acting like a sphincter. Medially and laterally, the orbicularis fibers run vertically and act to depress brow level. Laterally, orbicularis is the only muscle that depresses brow position.

The frontalis is the only elevator of the brow. It originates from the galea aponeurotica superiorly and interdigitates inferiorly with the orbicularis. Contraction raises this muscle mass and the overlying eyebrow, which is a cutaneous structure. The muscle is deficient laterally, so its primary lifting effect is on the medial and central portions of the eyebrow.

The periorbital region is the most expressive part of the human face. Subtle changes in eyebrow shape can profoundly affect facial appearance.¹

Because of the importance of periorbital expression, humans have historically resorted to any means at their disposal to alter their eyebrows. These have included eyebrow plucking and shaving, makeup, and tattoos.

Aesthetically, the eyebrow is only one part of the puzzle in the periorbital zone. Other variables include the presence of senile eyelid ptosis, the loss of upper sulcus orbital fat, and the accumulation excess of upper eyelid soft tissue (skin, orbicularis muscle, and orbital fat).

The preferred forehead will be devoid of vertical of transverse lines. It will be framed superiorly by a well-positioned aesthetically shaped hairline and inferiorly by well-positioned, attractively shaped eyebrows.

The “ideal” eyebrow shape is affected by ethnicity, gender, and the era in which we live (FIG 2). There are certain themes that define aesthetically pleasing eyebrow in the 21st century:⁷

Abnormally low eyebrows can be congenital or acquired over time through aging.

Age-related brow ptosis causes the forehead/eyebrow complex to encroach on the upper orbit, resulting in a pseudoexcess of upper eyelid skin. In response, patients subconsciously contract the frontalis to raise the eyebrows, leading to transverse forehead lines. This is accentuated with the presence of mild senile eyelid ptosis. Such patients will often present with a request for upper lid blepharoplasty.

Other lines in the forehead are caused by the glabellar frown muscles. Vertical lines are caused by the transversely oriented corrugator, horizontal lines are caused the vertically running procerus, and oblique lines are caused by the depressor supercilii and orbicularis.

Age-related brow ptosis is not universal. Up to 40% of people have relatively stable eyebrow position throughout life and are generally not candidates for brow lift surgery.⁸

Frontalis is the only lifting force to counter balance the various muscles and gravity that depress the brow level. The lateral portion of the eyebrow is particularly sensitive to this interplay because frontalis action is attenuated laterally and also because the security of lateral brow fixation to bone is inconsistent.^9,10 Poor soft tissue attachment with no muscular lift will inevitably lead to ptosis of the lateral third of the eyebrow.

Most patients will not be aware of the many factors involved in periorbital aging, and they may not want the multiple procedures required to treat all of these components. For that reason, identifying the main component of every patient’s periorbital aging is important. Old photographs are very helpful in helping the surgeon determine which age-related changes predominate.

Assessment is done with the patient awake and upright in the sitting or standing position. The following issues are evaluated: visual acuity, eyebrow and orbital symmetry, position of anterior hairline, thickness of scalp hair, transverse forehead lines, glabellar frown lines, thickness of eyebrow hair, eyebrow height, axis of the eyebrow (downward or upward lateral tilt), shape of the eyebrow (flat or peaked), passive and active eyebrow mobility, and the presence of old scars or tattoos. The upper eyelids should also be assessed for soft tissue redundancy, for upper sulcus hollowing, and for eyelid level (ptosis or lid retraction).

To identify patients with chronic frontalis contraction, examination should be done with eyes open and eyes closed. When the eyes are closed, the frontalis can be made to relax, revealing the true position and shape of the eyebrows. If the eyebrows are forcibly held in this position when the patient opens their eyes, the eyebrow-eyelid relationship without frontalis effect will be revealed.

A patient may be a candidate to have the entire brow complex lifted or more commonly to have only part of the eyebrow raised, thus improving eyebrow shape. Occasionally, in a patient who chronically looks angry, this may involve raising the medial brow only, but most commonly, it is the lateral third to one-half of the eyebrow that requires repositioning with little or no lift of the medial portion.