Eyebrows and Forehead

Structure

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The eyebrows form a critical landmark of the upper facial appearance and provide a unique quality in human facial anatomy. 1 Brow position and contour convey emotion and feeling and comprise an important part of body language. 2

At the junction of the forehead and the upper eyelid, the eyebrow is a transverse elevation of hair arched above the superior orbital rim. Technically, the eyebrow is considered part of the scalp and is divided into three anatomic parts: head, body, and tail. The eyebrows are formed by the superciliary ridge (brow ridge or supraorbital ridge) of the frontal bone, which is more prominent in males and often absent or less prominent in females. The lateral brow lacks this extra bony support, because the superciliary ridge extends only over the medial half to two-thirds of the orbit. Laterally, the brow is supported by fascial attachments to the temporalis fascia.

The skin of the eyebrow represents a transition zone between the thinner skin of the eyelids and the thicker skin of the forehead and scalp. The eyebrow skin is thick with a correspondingly thick subcutaneous fibrofatty layer such as that of the scalp, and it consists of more fibrous tissue than fat.

The two eyebrows are mirror images of each other. Eyebrow cilia are directed at different angles in the upper and lower eyebrow. 5 The upper rows grow down and laterally at an angle of <30 degrees from the vertical, whereas the lower most cilia grow up and laterally, also at an angle of <30 degrees. An abrupt reversal occurs when these cilia meet in the midline of the eyebrow. However, this reversal does not occur at the medial end of the eyebrow, where the eyebrow cilia sweep superolaterally.

The three types of hair in the eyebrow are (a) fine, vellus hair; (b) the slightly larger and lightly pigmented hair; and (c) the large terminal hair, also known as the supercilia. The fine vellus hairs form an effective moisture barrier to keep sweat from running downward into the eye. The fluid flow is redirected medially and laterally, away from the eye.

The supercilia give the eyebrow its apparent color and configuration. The supercilia are too large and too widely spaced to comprise a good moisture barrier. The horizontal and vertical eyebrow hair angulation should be kept in mind while planning incisions in the eyebrow region. Beveling the incision in a parallel fashion to the shafts of the hair will minimize the number of follicles transected. 5 A rich vascular plexus and abundant sensory nerve endings surround the follicle of each supercilium. Shaving or cutting the eyebrow hair does not affect its subsequent growth. In fact, full regrowth of a shaven eyebrow occurs within 6 months. 6

The skin of the eyebrow and glabellar region contains numerous sebaceous glands. Eccrine sweat glands are sparse, except for in the tail of the brow. This predominance of sebaceous glands causes an oily skin texture of the eyebrow.

, Male brows have a flat contour with more prominence and fullness laterally and a feathered appearance at the superior margin. Eyebrow hairs tend to get thicker and longer with age. The eyebrow hair in an elderly man is heavier and thicker than in an elderly woman. The female brow tends to be thinner and more arched than the male brow. Typically, the highest point generally occurs at the junction of the body and tail of the eyebrow, which is above the lateral limbus according to Westmore’s classic model., The female brow has a smoother superior margin of brow hair and rests above the orbital rim, especially in its temporal aspect. The male brow usually rests lower along the edge of the superior orbital rim.

The male and female eyebrows differ in both shape and position. 7 8 Male brows have a flat contour with more prominence and fullness laterally and a feathered appearance at the superior margin. Eyebrow hairs tend to get thicker and longer with age. The eyebrow hair in an elderly man is heavier and thicker than in an elderly woman. The female brow tends to be thinner and more arched than the male brow. Typically, the highest point generally occurs at the junction of the body and tail of the eyebrow, which is above the lateral limbus according to Westmore’s classic model. 9 Westmore also proposed that the medial extent of the eyebrow should reach a vertical line drawn from the medial canthus, and a tangential line connecting the lateral canthus and the lateral ala of the nose for the lateral extent of the eyebrow. The lateral and medial extent of the eyebrow should fall in the same horizontal plane. Cook et al. 10 contend that the arch above the lateral limbus makes the face look surprised and is unnatural. They concluded that the highest arch should lie more laterally in between the lateral limbus and lateral canthus. Several recent studies support this concept. 7 11 The female brow has a smoother superior margin of brow hair and rests above the orbital rim, especially in its temporal aspect. The male brow usually rests lower along the edge of the superior orbital rim. 8

The eyebrow corresponds to a specialized area of the superficial muscle plane of the face where the vertical fibers of the frontalis muscle and the horizontal fibers of the orbicularis oculi muscles interdigitate. 12 The position of the eyebrow represents a dynamic interplay between elevating and depressing forces. 13 The frontalis muscle is the main eyebrow elevator or retractor, and the depressors or protractors are the orbicularis oculi, corrugator supercilii, and the procerus

Eyebrow Depressors

Orbicularis oculi muscle.

Contraction of the orbicularis oculi muscle closes the eye and pulls the eyebrow down ( Fig. 1.1 ).

Figure 1.1. Superficial facial muscles and cutaneous landmarks (right upper lid orbicularis removed to illustrate deeper structures).

Corrugator supercilii muscle

, The more medial oblique head of the corrugator muscle is smaller and has vertically oriented fibers that insert into the medial brow. The transition between the transverse and oblique head fibers is indistinct., Stimulation of the transverse head moves the eyebrow medially and pulls the two eyebrows together, making the vertical and oblique furrows of the glabella. The oblique head of the corrugator acts as a depressor of the medial eyebrow and contributes to the formation of the oblique glabellar furrow. Weakening the medial portion of the corrugator contributes to medial brow elevation and can diminish glabellar frown lines.

The corrugator supercilii muscle is composed of two heads ( Fig. 1.1 ). The transverse head originates from the frontal bone near the superomedial orbital rim, anterior and slightly superior to the trochlea. It runs obliquely in a lateral and superior direction and inserts into the subcutaneous tissue superior to the middle third of the eyebrow, 13 14 The more medial oblique head of the corrugator muscle is smaller and has vertically oriented fibers that insert into the medial brow. The transition between the transverse and oblique head fibers is indistinct. 14 The frontal branch of the temporal division of the facial nerve (corrugator motor nerve) supplies the transverse head of the corrugator muscle, whereas the zygomatic branch of the facial nerve innervates the oblique head. 14 15 Stimulation of the transverse head moves the eyebrow medially and pulls the two eyebrows together, making the vertical and oblique furrows of the glabella. The oblique head of the corrugator acts as a depressor of the medial eyebrow and contributes to the formation of the oblique glabellar furrow. Weakening the medial portion of the corrugator contributes to medial brow elevation and can diminish glabellar frown lines.

Procerus muscle

A midline muscle overlying the glabella, the procerus muscle ( Fig. 1.1 ) arises from the nasal bone and the upper nasal cartilage, and travels superiorly to insert on the medial forehead skin. 15 Activation of these muscle fibers pulls the head of the brow inferiorly, causing the horizontal furrow of the glabella. The procerus muscle has innervations from the buccal branch of the facial nerve and is a primary brow depressor. 16 Weakening of the procerus muscle achieves significant medial brow elevation.

Depressor supercilii muscle

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Distinct from the orbicularis oculi and corrugator muscles, the depressor supercilii muscle also acts as a depressor of the eyebrow. It originates as two distinct heads from the frontal process of the maxilla, approximately 1 cm above the medial canthal tendon. It travels superiorly and inserts onto the dermis approximately 13 to 14 mm superior to the medial canthal tendon. The angular vessel passes between the two muscle heads. 17

Eyebrow Elevators

Frontalis muscle

The frontalis muscle ( Fig. 1.1 ) is a part of the occipitofrontalis musculofascial complex of the scalp, which includes the occipitalis muscle, galea aponeurotica muscle, and frontalis muscle. The vertically oriented fibers of frontalis muscle extend from the broad fibrous tissue of the galea aponeurotica just inferior to the hairline and insert into the supraorbital dermis. Contraction of the frontalis muscle can elevate the eyebrow more than 20 mm and also causes horizontal furrows across the forehead. These furrows do not extend to the temporal hairline because the frontalis muscle thins laterally and does not extend past the temporal fusion line to the tail of the brow. The lack of frontalis pull over the tail of the brow explains the common temporal brow ptosis seen so commonly in older adults. The frontal branch of the facial nerve innervates the frontalis muscle. (The course of the frontal nerve will be discussed later in this chapter.)

retro-orbicularis oculi fat pad

(ROOF) or eyebrow fat pad (

The galea aponeurosis joins the frontalis muscle anteriorly and splits around the frontalis muscle into a superficial and deep galea. The thinner superficial layer continues inferiorly as the anterior muscle sheath of the frontalis and orbicularis muscles, whereas the deep galea becomes the posterior muscle sheath. This deep galea layer divides inferiorly and encompasses the fat pad that lies beneath the interdigitation of the frontalis and orbicularis muscles and is termed the(ROOF) or eyebrow fat pad ( Fig. 1.2 ).

Figure 1.2. Relationship of galea aponeurosis, frontalis muscle, eyebrow fat pad (ROOF), and posterior orbicularis fascia.

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The ROOF is located in the supraorbital area mostly above the supraorbital rim and only a few millimeters below the rim, and it continues into the eyelid as the posterior orbicularis fascia 12 Fig. 1.2 ). This submuscular fat pad should not be confused with the subcutaneous fat, which is anterior to the muscle layer. With aging, involution changes can cause the ROOF to descend and the inferior aspect of the fat can prolapse into the eyelid. When this occurs, the fibrofatty ROOF can be mistaken for the more purely fatty preaponeurotic fat pad. This error in judgment can cause the orbital septum to be misidentified as the levator aponeurosis, which if mistakenly advanced, can result in marked lagophthalmos. Anteriorly, the posterior frontalis-orbicularis muscle fascia bounds the ROOF. Posteriorly, the fascial boundary of the ROOF is dense fibrous tissue, which extends inferiorly to the eyelid as the orbital septum 20 Fig. 1.2 ). Eyebrow fat contains both fibrous septae with interseptate fat-filled spaces and the branches of the facial nerve. This eyebrow fat pad continues laterally and inferiorly with the subsuperficial musculoaponeurotic system (sub-SMAS) fat in the malar region and the suborbicularis oculi fat (SOOF) of the lower eyelid. 21 A recent study by Hwang et al. 19 confirmed histologically that ROOF and SOOF were situated deep to the orbicularis oculi muscle and superficial to the orbital septum and periosteum. The group also demonstrated that ROOF and SOOF are distinct structures.

Anatomy of the Periorbital Region

The general anatomy of the non-globe periorbital region is depicted in Figure 1. The definitions for the terms utilized in describing the features within this region are listed alphabetically. The anatomy of the various structures is described in more detail below.

• Figure 1

• Figure 2

• Figure 3

Brow:

The soft tissue at the junction of the frontalis and orbicularis oculi muscles, overlying the bony supraorbital ridge.

Eyebrow:

The arch of hair on the brow (Fig. 2) [Goss, [1959]]. The eyebrows usually extend further laterally than medially, in relation to the eye, and are wider and thicker medially. Based on observed localized abnormalities of the eyebrow, it is useful to divide the eyebrow into three parts: medial, middle (central), and lateral. The hairs of the medial part are oriented laterally, while those of the middle (central) part are oriented superolaterally. The transition between the middle and lateral parts is less frequently visible. Some syndromes have unique patterns of aberrations in one or more of these three areas. The eyebrow is sometimes referred to as the supercilium.

Eye Spacing:

There is wide variation in interorbital distance and in the placement of the canthi [Cohen et al., [1995]]. A number of terms in this article address the nomenclature of these variations. Several of the terms are commonly confused (especially telecanthus and hypertelorism). Some of the variations are illustrated in Figure 3.

Eyelashes:

Hairs that emanate from the margins of the eyelids [Goss, [1959]].

Eyelid (Synonym: Blepharon, palpebra {plural: palpebrae}):

A fold of skin and its subcutaneous components that covers the anterior globe. The upper lid is bounded by the soft tissue overlying the inferior border of the bony supraorbital ridge and inferiorly by the lid margin. The lower lid is bounded by the soft tissue overlying the infraorbital rim and superiorly by the lid margin. A crescent-shaped crease on the upper eyelid represents the location of attachment of the levator palpebrae muscle to the orbicularis oculi muscle [Goss, [1959]].

Lacrimal Punctum {Plural: puncta}:

This structure represents the external aperture of the tear duct system. It can be absent, malpositioned, or obstructed [Ogawa and Gonnering, [1991]], and several terms below address these findings.

Note that the plurality of the terms is variable. The default chosen is to specify the singular form of the term unless the term relates to a pair of structures and only makes sense in the plural form (e.g., Eyes, closely spaced) or refers to a structure with many elements (e.g., Eyelashes, sparse). The plurality of the terms was ignored when they were alphabetized and the terms were grouped together (e.g., Eye and Eyes are grouped together, and not interrupted by Eyelashes).