Ronald J. Siegle

Introduction

A paralyzed and ptotic eyebrow, an oblique midforehead scar, focal alopecia in a brow, an asymmetric hairline—for the skilled reconstructive surgeon, these deformities would be considered complications of forehead reconstruction. For the unskilled and unknowledgeable surgeon, these are more likely to simply be written off as common sequelae of reconstruction.

Reconstructive surgery of cutaneous defects of the forehead may be simple or complex. Several goals must be considered: preservation of motor function (temporal branch of facial nerve) and, if possible, sensory nerve function; maintenance of the aesthetic boundaries of the forehead, including position and symmetry of the eyebrows and the frontal and temporal hairlines; and optimal scar camouflage by placement of scars in or adjacent to the hairline, eyebrows, and relaxed skin tension lines (RSTLs) whenever possible. This chapter reviews the anatomy of the soft tissue cover of the forehead and the principles of reconstruction of this aesthetic region of the face. The reader is also referred to a number of well-written review articles on forehead reconstruction, from many of which this author has learned and thus improved his expertise in reconstruction of this facial region.1–7

Anatomy

The skin of the forehead varies not only from person to person but also changes notably with aging and exposure to the sun. Beginning in the suprabrow area and moving toward the anterior hairline, forehead skin dermal thickness and sebaceous gland concentration decrease. This is manifested by a decreasing skin thickness and a less porous, less oily skin. In youth, the forehead skin is taut and smooth, with a shiny appearance. In contrast, older or sun-damaged skin has an increased mobility, a dull appearance, and rhytids; although aesthetically compromising, these features all facilitate reconstructive procedures.

The predominant muscle of the forehead aesthetic region is the anterior belly of the occipitofrontalis muscle. The vertical orientation of the skeletal muscle fibers is responsible for the transversely oriented RSTLs. Often quite prominent in younger individuals, the muscle thickness diminishes substantially with age. Extensive cutting of this muscle during reconstructive procedures may cause local palsies that have a prolonged recovery. Also of note is the often present anterior extension of the galeal median raphe. This fascial extension in the midforehead is devoid of muscle fibers and accounts for the often excellent aesthetic result that is attainable with vertical midline wound closures of the forehead. The other muscles in the forehead region include the orbicularis oculi, procerus, and corrugator supercilii. As a rule, transection of portions of these muscles is without major consequence.

The forehead is a richly vascularized region. It is supplied centrally by the right and left supratrochlear and supraorbital arteries and laterally by the anterior branch of the temporal arteries. These vessels are located in the subcutaneous tissue and are predictable in their location. Transection of these vessels during the elevation of random pattern cutaneous flaps should not be of any major consequence because of the ample collateral circulation of forehead skin.

Loss of nerve function, whether motor or sensory, has great consequence to the patient. The motor nerve to the frontalis muscle is the temporal branch of the seventh cranial nerve (Fig. 21-1). This nerve innervates the entire frontalis muscle and is most at risk for injury during flap elevation, not on the forehead, but rather over the zygomatic arch and in the temporal area. The thin skin and subcutaneous tissue in these areas cause the nerve to be close to the skin surface, particularly in thin or aged individuals. Development of flaps in the temporal region may transect the nerve if the flap is not cautiously elevated. On reaching the forehead, the nerve enters the frontalis muscle from its deep surface, and inadvertent transection of the nerve is much less likely. To prevent motor nerve injury, dissection of local cutaneous flaps of the forehead should be in the subcutaneous tissue plane or below the frontalis muscle and above the periosteum of the frontal bone.

The major sensory nerves of the forehead are the supraorbital and supratrochlear nerves, which run with their named arteries. After exiting their foramina in the sub-brow area, they pierce the overlying muscle and extend cephalad in the subcutaneous tissue. Transection of these nerves yields anesthesia distal to the point of injury. The anesthesia may extend posteriorly to the level of the parietal scalp. The numbness perceived by the patient is not only annoying but also potentially harmful because of loss of normal sensory feedback. To prevent sensory nerve damage in dissection of forehead cutaneous flaps, it is essential that the surgeon carefully undermine skin flaps in the superficial subcutaneous tissue plane. For larger flaps developed below the muscle, consideration should be given to placement of incisions peripheral to the path taken by these nerves.

Functional and Aesthetic Considerations

The first goal of forehead reconstruction is to maintain motor and sensory nerve function. Knowledge of forehead anatomy and proper flap design will help accomplish this goal the majority of the time. In some instances, sensory nerves will require transection, particularly in reconstruction of large skin defects, but this should be done only if no other effective reconstructive alternative is available. The surgeon should not burden the patient with a motor or sensory nerve deficit in exchange for a less complex reconstructive procedure that requires transection of important motor or sensory nerves. The compromised function of a nerve, particularly motor, should never be considered a routine consequence of reconstruction of the forehead. Regrowth of sensory nerves can be anticipated; however, complete transection of the supratrochlear or supraorbital nerve results in anesthesia of the distal forehead and scalp commonly lasting for 1 year or more.

On occasion, the surgeon is confronted with cutaneous defects of forehead skin in which the facial nerve branch to the frontalis muscle has been cut, yielding a ptotic eyebrow, facial asymmetry, and occasionally visual field limitation on upward gaze. Not all individuals are functionally compromised by a paralytic eyebrow ptosis. If individuals wear eyeglasses, they may adequately camouflage the appearance of a ptosis with their eyeglasses and the ptosis will not require surgical repair. However, for those situations with functional or significant aesthetic alteration, several techniques are available to elevate the eyebrow unilaterally. The author most commonly performs a direct eyebrow lift in which an ellipse of skin is resected from the suprabrow area to elevate the eyebrow approximately 4- to 8-mm higher than the opposite eyebrow. The more lax the forehead skin, the greater is the need to overcorrect the elevation. The inferior border of the skin ellipse is incised along the superior margin of the eyebrow parallel to the axis of the hair shafts. Horizontal mattress suspension sutures are placed between the sub-brow dermis and the forehead periosteum. Nylon sutures (5-0 clear) are passed through the periosteum approximately 1 cm above the desired point of eyebrow elevation.

Repair of the skin incision then follows with a layered closure, preferably by intracuticular suturing techniques. A second alternative for correction of eyebrow ptosis is to perform a procedure similar to a direct eyebrow lift, but incisions are made in the midforehead, thereby camouflaging the incisions in the horizontal creases of the forehead skin. Coronal forehead lifts for correction of unilateral eyebrow ptosis are not indicated.

In the last decade, the concept of facial aesthetic regions has greatly simplified and, more important, improved the outcome of facial reconstructive procedures. Facial aesthetic regions have borders that must be maintained to ensure facial symmetry. As a rule, a given aesthetic region is covered with skin that has identical or similar characteristics throughout. If “neighborhood skin” within the same aesthetic region can be recruited to repair a skin defect, optimal aesthetic results may be obtained. The forehead facial aesthetic region is defined peripherally by the juncture lines with the frontal scalp superiorly, the temporal scalp and temple laterally, and the eyebrows and glabella inferiorly (Fig. 21-2). The forehead is somewhat different from other facial aesthetic regions in that it has both an actual and perceived boundary line. Hairstyling can play a major role in forehead visibility. Bangs or a sweeping hairstyle can be used to cover all or part of the forehead. Thus, hairstyling may be used to camouflage a large area of forehead scarring and disfigurement.

In planning reconstruction of a cutaneous forehead defect, the surgeon must first ask what the aesthetic goals are. The specific aesthetic goals for forehead reconstruction are maintenance of eyebrow symmetry; maintenance of natural-appearing temporal and frontal hairlines; when possible, positioning of scars adjacent to or in hairlines and eyebrows; when possible, creation of transverse rather than vertical scars (except in the midline); and avoidance of diagonal scars.

Reconstructive Principles

In cases of skin cancer of the forehead, a forehead flap that is beautifully designed and has healed perfectly a few weeks after surgery is of no value if pathologic examination of the tissue excised shows that tumor is still present in the margins of the resection. As a micrographic surgeon, the author is fortunate to be able to remove skin cancers with immediate feedback concerning tumor margins and can ensure a tumor-free field before proceeding with reconstruction. There are other means to achieve margin control, such as traditional frozen sections. In addition, reconstruction can be delayed for several days until pathologic reports of permanently fixed specimens are available. The important message is that local tissue rearrangement in the form of cutaneous flaps should not be performed until successful tumor removal has been confirmed. Priorities in order of importance are to remove tumor completely, to maintain function, and to restore appearance.

The use of local anesthesia for surgery on the forehead is usually well tolerated. The anesthetic that is used most frequently is 1% lidocaine with 1 : 100,000 concentration of epinephrine. Many surgeons add sodium bicarbonate to this solution with a final concentration of 0.1 mEq/mL to minimize the pain of injection. There are several additional steps that can be taken to minimize the discomfort of infiltrative anesthesia. Complete forehead anesthesia may result from bilateral regional nerve blocks. Anesthetic is injected bilaterally beneath the eyebrow along the bony orbital rim from midline to a lateral point approximately two-thirds of the length of the eyebrow. Approximately 2 mL of anesthetic solution per side yields an anesthetic field extending from the eyebrow cephalically to the parietal scalp. Individual nerve blocks may be accomplished by injection of the subcutaneous tissue adjacent to the foramen of the supratrochlear or supraorbital nerve. Field blocks with injections placed just proximal to the surgical site will often yield distal anesthesia within a minute and allow painless injection of the remaining portion of the forehead. An important point to remember is that local anesthetics affect motor nerves. Thus, a lateral forehead nerve block may cause paralysis of the frontalis muscle, which in the intraoperative setting cannot be differentiated as to whether it is caused by surgery or local anesthesia. This paresis may last several hours, and therefore no corrective procedures for eyebrow ptosis are indicated until the cause of the ptosis is known.

Options for repair of cutaneous forehead defects include healing by secondary intention, primary wound closure, skin graft, and local or, uncommonly, distant flap. As a rule, the healing of the forehead by secondary intention, although adequate for midline defects, yields suboptimal scars elsewhere on the forehead. In addition to the midline, extreme lateral forehead and temple sites may heal beautifully by secondary intention.

Primary repairs of forehead defects are often possible. There is great variability in the laxity and availability of excess skin on the forehead. Redundant skin is more likely in older individuals and those with sun-damaged skin. Redundant forehead skin may be present in either the horizontal or vertical axis. Skin redundancy can best be determined by pinching and spreading of the forehead skin. Deep forehead furrows may contain relatively large amounts of redundant skin. If adjacent tissue is not adequate for primary wound repair, options include borrowing skin from regional sites (including the temple, scalp, and glabella) and use of skin grafts. Although skin grafts are an easy method of repairing large defects of the forehead, they usually yield suboptimal results because of poor color and texture match with the remaining forehead skin. Split-thickness skin grafts are appropriate for patients with skin cancer who are at high risk for recurrence. The skin graft facilitates accurate surveillance of the tumor site.

Flaps for Forehead Reconstruction

Cutaneous and musculocutaneous flaps are an excellent means to reconstruct forehead skin defects that cannot be repaired primarily. Flaps can usually be harvested from the forehead skin adjacent to the defect, thus maximizing aesthetic outcome. Because there are a number of different flaps that can be created, one can usually be designed that offers limited impairment of function. When such flaps are used, recovery is usually rapid and without motor or sensory nerve deficit. In general, small flaps should consist only of skin and subcutaneous tissue. Undermining of the flap is carried out in the superficial subcutaneous tissue plane. Although this maintains the subdermal plexus, it creates more bleeding and is more surgically challenging than dissection beneath the frontalis muscle because of the need to dissect around the neurovascular bundles.

Musculocutaneous flaps are dissected beneath the frontalis muscle and are required for repair of larger defects and in situations in which a cutaneous forehead flap might result in excess wound closure tension. Musculocutaneous forehead flaps can be widely undermined below the fascia of the frontalis muscle in a relatively avascular tissue plane. Careful flap design is necessary to prevent or to limit transection of sensory nerves. Undermining at this deep level may provide only limited tissue for direct advancement because of the constraints of the overlying fascia of the frontalis muscle. Musculocutaneous flaps, in contrast to cutaneous forehead flaps, involve mobilization of tissue over a fixed infrastructure, specifically the frontal bone. Thus, for larger defects repaired with musculocutaneous forehead flaps, there may be moderate to extreme tension on the closure line. Despite this, most flaps heal well because of their abundant vascularity.

Advancement is the most common design of flaps used for forehead reconstruction. Among the main benefits of advancement flaps are maintaining a natural contour of the forehead, facilitating optimal scar placement in horizontal forehead creases, and usually providing an adequate source of skin for reconstruction. The two major disadvantages of advancement flaps are the requirement for extensive undermining for larger flaps and the need for multiple incisions. Multiple designs for advancement flaps are possible, including unilateral, bilateral, subcutaneous tissue pedicle, and A-T and O-T repairs. Bilateral advancement flaps often take the form of an H-plasty if two parallel incisions are made to create the flaps. If single incisions are used, repair assumes the form of a T-plasty (see discussion in Chapter 6).

Rotation flaps are often useful for forehead reconstruction because they take advantage of the curvature of the frontal bone. They are usually designed as large flaps and thus offer reliable vascularity to the flap. The major disadvantage of a cutaneous forehead rotation flap is the lengthy incision line required to create the flap, which is often diagonal to the horizontal creases of the forehead. Multiple designs of rotation flaps are possible, including unilateral and bilateral. Bilateral rotation flaps often take the form of an O-Z closure.

Transposition flaps, the most common flaps used to repair cutaneous defects in other areas of the face, play a lesser role in forehead reconstruction. They may be used in the glabellar and lateral forehead areas but often create suboptimal scars because the scars are frequently not parallel to RSTLs. As a consequence of the need to close the flap donor site, scars may be positioned in a less than ideal orientation. Transposition flaps also frequently cause a slight contour abnormality and are usually transferred under excess wound closure tension. The designs most commonly used include the rhombic and the 30° transposition flaps.

Conceptually dividing the aesthetic region of the forehead into three aesthetic units greatly simplifies the thought process and decision-making used for flap selection. The forehead can topographically be divided into the following units: midline; paramedian, extending over the convexity of the forehead from midline to the midpupillary line; and lateral forehead, extending from the midpupillary line to the juncture with the temple (see Fig. 21-2).