4Forehead and Temple Reconstruction

Joseph F. Sobanko, Ashwin Agarwal, and Christopher J. Miller

The forehead has a rectangular shape bounded superiorly by the frontal hairline, caudally by the nasal root and eyebrows, and laterally by the bony prominences of the temporal crest. The upper forehead has a shinier texture with thinner dermis and fewer sebaceous glands than the lower forehead.¹ Fibrous connections tether the dermis of the forehead skin to the underlying frontalis muscle and limit mobility.

The temple, on the other hand, has a triangular shape with its base at the zygomatic arch, a medial limb along the orbital rim and temporal crest, and a lateral limb at the temporal hairline. The skin of the temple has dermal thickness and sebaceous gland density similar to the upper forehead, but it is more mobile due to looser connections with the underlying superficial temporal fascia.

4.1.2 Muscles of the Forehead and Temple

The forehead has four underlying muscles of facial expression: the frontalis, procerus, the corrugator supercilii, and superior portions of the orbicularis oculi. The frontalis muscle originates at the anterior portion of the galea aponeurotica of the scalp and inserts into the subcutaneous tissue and skin of the lower forehead and brows. Its fibers also interdigitate with the procerus, corrugator supercilii, and orbicularis oculi muscles. As the galea descends from the scalp, it splits to invest the frontalis muscle with fascia on its superficial and deep surfaces. Contraction of the frontalis muscle raises the eyebrows and produces horizontal rhytides or relaxed skin tension lines (RSTLs). The procerus muscle originates on the nasal bone and inserts on the frontalis muscle. Contraction of the procerus draws down the medial angle of the eyebrows and creates transverse rhytides at the nasal root. The corrugator supercilii muscles have their origins at the medial end of the superciliary arch and insert on the skin of the medial brows. They reside deep to the frontalis muscle. Contraction of the corrugator supercilii muscles pulls the brow inferiorly and medially and creates oblique rhytides between the brow and the glabella. The superior aspects of the orbicularis oculi muscles, which serve to close the eyelids forcefully, lay superficial to the frontalis muscle.

There are no muscles of facial expression specific to the temple. The superficial temporal fascia, which is continuous with the frontalis muscle, lies deep to the subcutaneous fat of the temple and separates the skin from the underlying temporalis muscle. Because of this, contraction of the temporalis during mastication does not create overlying rhytides. Instead, RSTLs on the temple occur from contraction of the adjacent orbicularis oculi and frontalis muscles. Radial rhytides on temple skin are a result of dynamic muscle activity of the orbicularis oculi muscle.

In both the forehead and temple cosmetic units, actinic damage, age, and muscle use contribute to the permanent etching of rhytides, even at rest, consequently providing convenient sites to hide surgical incisions.

4.1.3 Blood Supply to the Forehead and Temple

The internal carotid artery supplies blood to the forehead via the paired supratrochlear and supraorbital arteries. These vessels share numerous anastomoses as they course cephalically in the subcutaneous fat of the forehead. Pushing the forehead skin toward the midline creates vertical and oblique wrinkles corresponding to the path of the underlying arteries in the glabellar region.

The supratrochlear artery is a terminal branch of the ophthalmic artery from the internal carotid arterial system. It exits the orbit by piercing the orbital septum at the superomedial orbital rim within 5 mm to a vertical line drawn at the medial canthus.² Its pulse can be palpated at its exit point found approximately 12 mm (range: 10.2–14.5 mm) superior to the medial canthus.³ It has mean diameter of 0.9 mm.³ Some surgeons use this landmark and even ultrasound to identify the supratrochlear artery for the formation of the paramedian forehead flap.

After emerging from the septum, the supratrochlear artery travels superficial to the periosteum and corrugator supercilii muscle and deep to the orbicularis oculi and frontalis muscles.⁴ It pierces the orbicularis oculi and frontalis muscles to reach the subcutaneous fat between 10 and 25 mm superior to the supraorbital rim.^2,​5 On the lower forehead, the artery and its branches travel in the deep subcutaneous fat closer to the frontalis muscle.^2,​5 On the upper two-thirds of the forehead, the artery approaches the dermis as it courses cranially past the junction of the sagittal and coronal sutures at the top of the skull.⁶ Along its course, the supratrochlear artery has branches that communicate with numerous vessels, including the angular, supraorbital, paracentral, and central arteries.²

The surgeon can utilize topographic landmarks to identify the course of the supratrochlear artery. The most prominent glabellar frown line corresponds to the junction of the medial corrugator and procerus muscles, and can be accentuated by pushing the medial brows inferomedially toward the midline.⁷ The supratrochlear artery is located anywhere from this glabellar frown line to 6 mm laterally.⁷

The supraorbital artery exits the orbit through a foramen or notch 30 mm lateral to the midline and has a mean diameter of 0.84 mm. It enters the corrugator supercilii muscles and divides into superficial and deep branches, most commonly at the level of the supraorbital rim. The superficial branches travel through the corrugator, orbicularis oculi, and frontalis muscles before becoming superficial to the frontalis. It pierces the frontalis muscle approximately 30 mm above the supraorbital rim and transitions to the subcutaneous fat between 40 and 60 mm above the rim to reach the superior third of the forehead. The supraorbital artery gives an average of two to four superficial branches that supply the frontalis muscle.⁸

The deep branches of the supraorbital artery arise at the level of the supraorbital rim and travel cranially just above the periosteum and within deep layers of the subgaleal fascia to perfuse the pericranium and fascia. Flaps designed in this area and undermined in a subgaleal plane just beneath the frontalis muscle can preserve these deep branches of the supraorbital artery by elevating muscle but leaving down the loose areolar connective tissue atop the periosteum.

Of note, the supraorbital and supratrochlear arteries share many rich anastomoses across the medial and lateral forehead as they travel cranially to the scalp. They form a vascular arcade across the glabellar and nasal regions via connections with the bilateral angular arteries of the central face. Further, a supraorbital plexus approximately 3 mm above the supraorbital rim connects the supraorbital, supratrochlear, and dorsal nasal arteries from the nasal sidewall.⁶ Anastomoses also exist between distal deep branches of the supraorbital artery and the superficial temporal artery.

The temple subunit is similarly perfused by an anastomotic vascular network. Temporal skin and superficial temporal fascia are supplied by branches of the zygomatico-orbital, zygomaticotemporal, zygomaticofacial, and transverse facial arteries, all of which originate from the superficial temporal artery of the external carotid system. This network communicates with the deep temporalis fascia via perpendicular penetrating vessels.

4.2 Preservation of Sensory and Motor Function

4.2.1 Sensory Function

The STN and SON of the ophthalmic division (V1) of the trigeminal sensory nerve (cranial nerve [CN] V) provide sensation to the forehead and frontal scalp. An understanding of the location and course of the SON and STN is important for dermatologic surgeons, as surgery or reconstruction in this area can lead to transection that results in paresthesias, pruritus, or traumatic neuroma formation.⁹ Nerve injury leads to anesthesia extending in a column from the point of injury to the frontal scalp, although nerve regrowth and collateral formation may restore sensation months later.

The frontal nerve of CN V1 divides within the orbits into the SON and the STN after passing through the superior orbital fissure. The SON innervates the upper eyelid, forehead, frontoparietal, and vertex scalp, and emerges through a supraorbital notch or foramen on average around 4 mm above the superior orbital rim⁹ and approximately 2.6 cm from the midline. A vertical line drawn superiorly from the pupil is one method of mapping the path of the nerve. The SON then divides a few millimeters above the orbital rim into a superficial and a deep branch. The superficial branch courses through the corrugator supercilia before eventually traveling beneath the frontalis muscle. Many smaller branches emerge from this superficial branch and pierce the frontalis muscle in a fanlike distribution at around 2.6 cm above the superior orbital rim to innervate the forehead. The medial branches of this superficial SON branch cross-innervate a shared territory with the STN.⁹ Meanwhile, the deep branch of the SON courses more laterally after emerging from the supraorbital rim and remains subgaleal, deep to both the frontalis and the corrugators to innervate the vertex and frontoparietal scalp. Careless undermining below the frontalis muscle can injure this nerve branch and affect sensation to the frontal and vertex scalp. Forehead sensation will remain intact as the superficial branch does not travel below the galea.

The more medially located STN provides sensation to the skin and underlying tissue of the glabella, lower forehead, upper eyelid, and conjunctiva. It exits the orbit through the frontal notch or foramen approximately 4 mm cranial to the superior orbital rim and 18 mm from the midline. The STN then travels cranially approximately 1.6 cm from midline.¹⁰ To avoid transection, a similar anatomic danger zone can be considered in an area spanning 3 cm across the glabellar midline. After emerging from the orbit, the nerve separates into two branches within the retro-orbicularis oculi fat before penetrating the corrugator and branching into multiple smaller endings.

Sensation to the lateral forehead and temple is provided by the zygomaticotemporal, zygomaticofacial, and auriculotemporal nerve branches of the trigeminal nerve. Both the zygomaticotemporal and the zygomaticofacial nerve originate from the zygomatic nerve of the maxillary division (V2) of CN V as they branch at the level of the lateral orbit. The zygomaticotemporal nerve courses through the zygomaticotemporal foramen to enter the temporal fossa and finally emerges approximately 22 mm above the zygomatic arch to innervate the lateral forehead and temple.¹¹ During its course, it also communicates with the zygomaticofacial and auriculotemporal nerves.

The auriculotemporal nerve contributes to innervation of the posterior temple. It courses over the posterior zygomatic arch, posterior to the temporomandibular joint, and then travels cranially within the temporoparietal fascia anterior to the external auditory canal. For much of its path, the auriculotemporal nerve can be found in proximity to the superficial temporal artery. Moving cephalad, both the auriculotemporal nerve and the superficial temporal artery become superficial to the superficial temporal fascia.¹¹ The superficial temporal branch is the terminal ending that innervates temple skin, and emerges at a distance from the tragus of approximately 15 mm cranially and 7.5 mm medially.¹²

4.2.2 Motor Function

The temporal branch of facial nerve provides motor function to the frontalis muscle, the upper portion of the orbicularis oculi muscle, corrugator supercilii, and temporoparietalis muscles. In most patients, it is the single innervating branch to the frontalis muscle. Injury to the temporal nerve results in ptosis of the skin of the brow and upper eyelid with noticeable facial asymmetry and potential obstruction of the superior visual field. The facial nerve (CNVII) travels through the temporal bone of the skull before it exits the stylomastoid foramen and delivers the posterior auricular branch behind the ear. It will emerge from the parotid gland approximately 2.5 cm anterior to the tragus. The temporal nerve then runs obliquely 1.5 cm lateral to the lateral orbital rim and deep to the superficial temporal fascia before innervating the lateral undersurface of the frontalis muscles.

Drawing a line from 0.5 cm below the tragus to 1.5 cm above the lateral brow approximates the course of the underlying nerve.¹³ In this region, the nerve is most at risk of transection after exiting the parotid gland and traveling just below and over the middle zygomatic arch, where it is protected only by thin overlying superficial temporal fascia through the temple and lateral forehead.¹⁴ Usually the facial nerve branches run between the superficial musculoaponeurotic system (SMAS) and the deep muscular fascia, and are therefore susceptible to injury in areas without overlying muscle. Undermining superficial to the superficial temporal fascia protects the temporal branch of the facial nerve.

4.3 Achieving Reproducibly Excellent Cosmetic Results

Adhering to key principles optimizes outcomes for forehead and temple reconstruction. Preserving the position and symmetry of the eyelids and brows is paramount. Restoring contour to the normally smooth surfaces of the forehead and temples is equally important. Hiding incisions along the cosmetic subunit boundaries and RSTLs of the hairline, brow, and orbital rim improves cosmesis. However, these incisions must not compromise free margin position or skin contour. Horizontally oriented linear closures on the forehead might align with RSTLs, but they may also cause ipsilateral and asymmetric brow elevation, especially for defects closer to the brow. Following these principles with sound surgical technique minimizes the visibility of forehead and temple scars.

After taking such anatomic considerations into account, push the wound edges toward each other to see if they approximate. If so, primary linear closure or a sliding flap offers the most reproducible results. Next, observe the effect of various tension vectors on the nearby free margins of the brow and eyelid, and choose a tension vector that preserves their position and contour. On the forehead, particularly for defects near the brow, most reconstructions recruit skin from lateral to medial along a horizontal vector to avoid elevating the brow. On the temple, the preferred tension vector is usually vertical, recruiting skin from inferior to superior. Subsequently, assess opportunities to hide scars in cosmetic subunit junction lines along the brow and hairline or in RSTLs. Consider extending wounds to the edges of the hair or brow to disguise scars. Also, take into account patient history of poor wound healing and donor skin quality (e.g., prior radiation) to predict the impact of closure tension on wound healing. Finally, choose surgical materials appropriate for the wound (Box 4.3).

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