Eric M. Genden
INTRODUCTION
Prior to the introduction of free tissue transfer, local and regional flaps represented the primary source of tissue for reconstruction of the lateral skull base. While free tissue transfer has supplanted many of the unreliable local flaps, the temporalis muscle flap (TMF) and temporoparietal fascia flap (TPFF) remain popular donor sites for reconstruction of the skull base. These donor sites provide a reliable source of well-vascularized tissue that can be used to reconstitute dural defects, fill soft tissue defects, or support the brain in the case of a cranial defect.
The TPFF was initially described more than a century ago. It is a thin, highly vascular layer of connective tissue immediately deep to the subdermal fibroadipose tissue of the scalp. The TPFF is continuous with the occipitofrontalis and galea superiorly, and below the zygomatic arch, it extends into the superficial musculoaponeurotic system (Fig. 41.1). Deep to the TPFF is a loose areolar layer that separates the TPFF from the deep temporal fascia. The blood supply to the TPFF is the superficial temporal artery. The vascular pedicle provides a rich vascular network to the flap but also limits the arch of rotation. Although the flap can be rotated to cover the lateral aspect of the skull base, it will not reach the central skull base.
FIGURE 41.1 The temporoparietal fascia is a superficial vascularized tissue flap that is located immediately deep to the subcutaneous tissue of the scalp. The temporalis muscle is found deep to the temporalis muscle fascia.
Like the TPFF, the TMF is a reliable, myofascial flap that was also described more than a century ago. The vascular supply is the deep temporal artery, which originates from the internal maxillary artery (Fig. 41.2). The temporalis muscle lies deep to the temporoparietal fascia. It is a broad, radiating muscle that arises from the temporal fossa and from the deep surface of the temporal fascia. Its fibers converge inferiorly to form the tendon, which passes deep to the zygomatic arch and inserts into the medial surface of the coronoid process. The flap can be raised up and pedicled only on the coronoid process. This improves the arc of rotation to reach the paramedian aspect of the skull base.
FIGURE 41.2 The vascular supply to the TPFF is the superficial temporal artery and vein; however, the vascular supply to the TMF is the deep temporal artery derived from the internal maxillary system.
I find that these flaps provide an excellent source of well-vascularized tissue that can be used for skull base reconstruction. They are reliable, and the donor site is well tolerated.
HISTORY
There are several important issues that must be considered when taking a history. The first relates to prior surgery. The advantage of the TPFF and the TMF is that they are often preserved in spite of prior surgery. As part of the history, it is important to determine if the patient has had prior cranial base surgery that may have compromised the pericranial flap. In such a case, the TPFF or TMF may be used for reconstruction of the lateral skull base. A careful history will often determine if the pericranial flap has been previously used for reconstruction. A second aspect of the history relates to the blood supply of these two flaps. The TPFF receives its blood supply from the superficial temporal artery and vein. In contrast, the TMF receives its blood supply from the deep temporal artery and vein. In the former case, if the external carotid artery has previously been ligated, the TPFF will not be viable. In the latter case, if the internal maxillary artery has been previously sacrificed, then the blood supply to the TMF will be compromised. A history of previous trauma to the donor site should be sought.
PHYSICAL EXAMINATION
The physical examination should be directed toward an evaluation of the external carotid artery and the lateral skull base region. Evidence of scarring or prior surgery should be carefully noted to determine if there has been a compromise in the blood supply to the temporalis muscle or temporal parietal fascia. Physical examination should also include a careful evaluation of the defect. While both the temporal parietal and the temporalis flaps are well vascularized, the arc of rotation and reach to the midline is limited. Both flaps are ideal for lateral temporal bone and lateral cranial base defects; however, they are not well suited for medial defects of the cranial base.
INDICATIONS
The indications for the TPFF and TMF are for defects of the lateral skull base. The TPFF is a well-vascularized flap that is ideal for reconstitution of defects of the dura. In contrast, the TMF is bulky but well vascularized. I tend to use the TPFF in cases where dural reconstruction is required. I reserve the TMF for defects that require restoration of bulk.
CONTRAINDICATIONS
The contraindications to the use of these flaps relates to the blood supply. In cases where the internal maxillary artery or external carotid artery had been sacrificed, the use of the temporalis and TPFFs is contraindicated.
PREOPERATIVE PLANNING
The preoperative planning begins by understanding the size, location, and the characteristics of the defect. Because of the limited arc of rotation and reach, defects of the lateral temporal bone, mastoid, orbitocranial segment, and the orbit are best suited for these flaps. I often Doppler the superficial temporal vascular system at some point preoperatively because there is a small proportion of patients who will have a vascular anomaly wherein the superficial temporal vein is not well developed. Although this vascular anomaly is rare, I like to know this before embarking on the harvest. Additionally, Doppler examination also assures me that the vascular system has not been compromised during prior surgery.
SURGICAL TECHNIQUE
The Temporoparietal Fascia Flap
This flap is harvested through a vertical incision with distal “Y” incision to provide optimal access to the underlying fascia, vascularized pericranial bone graft, and, if necessary, a vascularized skin paddle (Fig. 41.3). The fascia of the flap lies immediately deep to the subcutaneous tissue of the scalp. As a result, careful dissection is required to separate the subcutaneous skin of the scalp from the underlying fascia (Fig. 41.4). Careful attention to the superficial temporal artery and vein are necessary to prevent injury to the vascular supply of the flap. The flap can be raised as far as necessary to obtain a flap that is an appropriate size. Once the temporal parietal fascia is exposed (Fig. 41.5), the peripheral incision is made and dissection between the underlying fascia and the deep temporalis fascia is developed.
FIGURE 41.3 The flaps are accessed via a “Y” incision made on the lateral aspect of the parietal scalp. This provides access to the TPFF, TMF, and, if required, a vascularized skin flap and/or a vascularized pericranial bone graft.
FIGURE 41.4 The temporoparietal fascia is a superficial vascularized tissue flap that is located immediately deep to the subcutaneous tissue of the scalp. In this photo, the TPFF and the vascular supply are seen through the incision.
FIGURE 41.5 The TPFF is rotated inferiorly, and the temporalis muscle fascia is exposed.
The TPFF/TMF system is versatile and provides the opportunity to harvest a composite graft composed of a vascularized skin paddle with or without a vascularized cranial bone graft (Fig. 41.6). Composite grafts are useful for orbital reconstruction when a bone graft is indicated to support the orbit and skin is required to address a contracture ectropion (Fig. 41.7). Alternatively, the TPFF can be used as a sling to support the orbit (Fig. 41.8).
FIGURE 41.6 The photo demonstrates a TPFF–bone–skin composite graft to be used for orbital reconstruction.
FIGURE 41.7 The composite flap can be positioned such that the skin augments the infraorbital deficiency while the vascularized bone graft is used to support the orbit. This technique is particularly useful in the radiated tissue bed.
FIGURE 41.8 The TPFF can also be used as a sling to support the orbit.
POSTOPERATIVE MANAGEMENT
Postoperatively, I place a suction drain and leave that in place for 1 to 2 days. I close the wound with staples because sutures are often difficult to remove in the hair-bearing areas of the scalp.
COMPLICATIONS
Complications are rare; however, when harvesting the TPFF, if you elect to use cautery, alopecia may result from damage to the hair follicles. Cautery can be used, but I would recommend a low setting. If the scalp flaps are too thin, another complication is necrosis of the distal skin edges. For this reason, I use the “Y” design incisions to prevent wound necrosis as a result of compromised blood supply. Finally, when harvesting the temporalis muscle, the loss of muscle volume can result in a hollowing defect of the parietal scalp. I typically raise the TPFF as a separate flap when I plan to use the TMF so that I can use the TPFF to fill the muscle donor defect.
RESULTS
The results using this flap have been excellent. Both flaps are reliable because of the axial pattern blood supply. They provide an excellent bed for skin grafting and coverage of a radiated defect (Fig. 41.9A–D).
FIGURE 41.9 A. This photo demonstrates the TPFF being raised for coverage of a radiated auriculectomy and mastoid defect. B. The graft can be used to cover the defect, and a preformation can be made to preserve an external canal. C. A skin graft is placed over the TPFF. D.One-week postoperative evaluation demonstrates the healing graft. This bed will be prepared for osseointegrated implants and an auricular prosthesis.
PEARLS
• The TPFF has a distinct reach limited by the arc of rotation; however, the TMF arc of rotation can be increased by removing a segment of the zygoma or by transecting the coronoid attachments.
• TheTPFF is ideal for soft tissue coverage of a nonhealing mastoid cavity.
• TheTPFF can be used to fill in the donor defect left following harvest of the TMF.
• The TMF is ideal for reconstructing orbital defects following orbital exenteration.
PITFALLS
• TheTPFF is thin and richly vascular. The initial incision through the scalp should be performed with care so as not to injure the nourishing vessels.
• Raising the TPFF with a cautery may result in alopecia.
• If you are planning to transect the coronoid process to increase the TMF arc of rotation, be careful not to injure the vascular pedicle that lies deep to the muscle.
INSTRUMENTS TO HAVE AVAILABLE
• Standard head and neck surgical tray
• Reciprocating saw if a coronoid release is planned.
SUGGESTED READING
Marzo SJ, Leonetti JP, Petruzzelli GJ, et al. Closure of complex lateral skull base defects. Otol Neurotol 2005;26(3):522–524.
Smith JE, Ducic Y, Adelson RT. Temporalis muscle flap for reconstruction of skull base defects. Head Neck 2010;32(2): 199–203.
Collar RM, Zopf D, Brown D, et al. The versatility of the temporoparietal fascia flap in head and neck reconstruction. J Plast Reconstr Aesthet Surg 2012;65(2):141–148.