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Pericranial Scalp Flap


Introduction

Surgical extirpation and reconstruction represent the shared common core goals in both open and endoscopic anterior skull base surgery. Successful operative intervention requires thoughtful planning in the context of the patient’s anatomy, pathology, and comorbidities.

It is important to realize that the goals for the treatment of benign processes differ from those of malignant processes. Although gross total resection is always favored, surgical decompression with attempts at complete surgical excision without undue morbidity should always be the default with benign pathologies. In contrast, the treatment of malignant processes requires clear surgical margins.

Reconstructive efforts of the skull focus on the watertight separation of the cranial cavity from the upper aerodigestive/sinonasal tract. This separation is required to minimize the risk of postoperative cerebrospinal fluid (CSF) leak and associated sequelae such as meningitis and/or pneumocephalus. Reconstruction should also provide the obliteration of dead space, preservation of function, and restoration of cosmesis.

An array of skull base reconstruction options exists ranging from acellular grafts to vascularized flaps. This chapter will focus on the pericranial flap (PCF), a vascularized pedicled flap based on the supraorbital and supratrochlear arteries. This versatile flap has been used in a multitude of applications throughout the skull base and head and neck, and often represents the primary reconstructive choice in open anterior skull base procedures and the primary extranasal reconstructive choice in endoscopic anterior skull base procedures. It should be noted that the galeopericranial flap is also a vascularized pedicled flap based on the supraorbital and supratrochlear arteries. In addition to including the pericranium and immediately superficial loose areolar tissue, this flap includes the galea, thereby providing the reconstructive surgeon with a thicker pedicled flap.

Key Operative Learning Points

  • 1.

    The PCF is a vascularized pedicle flap based on the supraorbital and supratrochlear arteries and can be used in open and endoscopic anterior skull base reconstruction.

  • 2.

    The pericranium includes the calvarial periosteum and associated areolar tissue lying deep to the galea. The flap can be elevated and used without risk to the remaining scalp.

  • 3.

    The endoscopic-assisted PCF can be accessed and elevated using an array of incisions. We favor a trichophytic incision at our institution. When used in the setting of an endoscopic skull base resection, only half of the pericranium should be used, thereby maintaining an additional PCF option for future potential usage.

  • 4.

    Although an extended PCF can be elevated via open or endoscopic techniques, with a length adequate to reach clival defects, it is most frequently used for defects in the anterior cranial fossa and sella.

Preoperative Period

History

  • 1.

    History of Present Illness

    • Patients who present to the skull base surgeon often require a multidisciplinary approach to ensure accurate diagnosis and evaluation for optimal therapy. A detailed description of this critical portion of the evaluation is outside the scope of this chapter, but should focus on identifying clinical features that afford insight into the clinical progression, involved primary and adjacent structures, and the potential for regional or distant disease. This information should guide further investigations and frame patient counseling.

  • 2.

    Past Medical History

    • After identifying those patients who require anterior skull base surgery for which a PCF is considered, several factors must be taken into account.

      • a.

        Prior interventions that may affect the viability, presence, or healing capacity of the PCF and/or scalp.

        • 1)

          Prior maxillofacial trauma that could have disrupted the vascular supply.

        • 2)

          Prior transcranial or endoscopic surgery for which a PCF was used or transgressed. At our institution in the setting of a previously used PCF where a contralateral flap is not available, consideration of other reconstructive options such as a tunneled temporoparietal fascia flap or free tissue transfer is required.

        • 3)

          Prior radiation therapy (including the scalp) that could affect wound healing or increase the difficulty of flap elevation must be considered. Of note, the report of a recent review indicated that there was no significant difference in the rates of CSF leak between those receiving radiation therapy (8.1%) and those not receiving radiation therapy (2.6%).

      • b.

        Medical Comorbidities

        • 1)

          Diabetes mellitus, hypercortisolism, poor nutritional status, and cigarette smoking are risk factors for delayed wound healing and should be taken into account by the surgical team.

      • c.

        Medications

        • 1)

          All efforts should be made to hold antiplatelet and anticoagulants prior to surgical intervention to minimize the risk of excessive bleeding or the development of a hematoma in the donor site or surgical site.

Physical Examination

A comprehensive physical examination is of upmost importance when evaluating patients for skull base surgery. The physical examination should consider findings that indicate the degree of tumor extension including local mass effect and cranial nerve neuropathies. A thorough review of these features is outside the scope of this chapter, but a specific notation should be made regarding evaluation of the scalp for potential development of a PCF.

  • 1.

    Evaluation of the scalp

    • a.

      Prior incisions or scars should prompt directed questioning to ascertain the likelihood of a viable PCF. Suspected damage to the vascular supply or prior usage essentially eliminates its use in reconstruction of the skull base.

    • b.

      Evaluation of the hair and hairline should also be noted, because this will help the reconstructive surgeon plan the incisions for flap access. Additionally, the facial skeleton and position of the calvarial convexity should be noted, because an incision placed anterior to or posterior to the convexity may make complete elevation of the flap challenging when using an endoscopic-assisted approach.

  • 2.

    Nasal endoscopy

    • a.

      Bilateral sinonasal endoscopy provides the reconstructive surgeon with critical information regarding the location of the tumor and helps to determine the availability of intranasal vascularized flap options (i.e., nasoseptal flap [NSF]), which are often unavailable in revision surgery or when malignant tumors involve the nasal septum.

Imaging

  • 1.

    Anatomic imaging

    • a.

      The evaluation of the primary site requires at least a computed tomography (CT) maxillofacial scan with image guidance protocol and a complementary contrasted magnetic resonance imaging (MRI) scan of the brain with image guidance protocol. These studies are critical in allowing the skull base team to assess the burden of disease, surrounding critical neurovascular structures, candidacy for resection, and the projected surgical defect.

    • b.

      Such studies can also provide clues to the availability of intranasal vascularized flaps that may not be obvious on sinonasal endoscopy.

  • 2.

    Imaging studies for staging should be sought in patients with malignant tumors to ensure appropriate treatment goals and treatment planning.

Indications

  • 1.

    In open transcranial anterior skull base surgery, the PCF remains the most frequently used flap with its passage inferior to the supraorbital bone segment into the surgical defect with suturing and/or apposition to the resection margin.

  • 2.

    Endoscopic anterior skull base surgery

    • Vascularized reconstruction produces lower rates of postoperative CSF leaks compared with free grafts in the presence of large dural defects. It is preferable in repair of defects localized to the clivus and in patients with high-flow intraoperative CSF leaks.

    • The PCF is the primary extranasal vascularized pedicle flap used at our institution when intranasal options are not available in the presence of large dural defects and/or high-flow CSF leaks localized to the anterior fossa/ethmoid roof and sella.

    • Using radiological studies, the distance of the defect, locations, and size estimates of the PCF needed to fill defects were performed. Using a 3-cm correction factor accounting for flap transposition through the nasionectomy and retraction, the following flap length estimates were needed to reach the following defects: 11.31 to 12.44 cm for anterior fossa defects, 14.31 to 15.57 cm for sellar defects, and 18.3 to 20.42 for clival defects.

Contraindications

  • 1.

    Prior compromise of the vascular supply.

  • 2.

    Prior flap usage without a contralateral option or flap transgression.

  • 3.

    Defects localized to the posterior fossa/clivus; the defect generally lies at the distal-most aspect of an extended flap with the possibility of poor or inadequate coverage of the defect.

Preoperative Preparation

Prior incisions of the face/scalp should be evaluated to determine whether the blood supply (supratrochlear, supraorbital vessels) to the PCF is intact. Alternative flaps or materials should also be considered in reconstructing the skull base in the event of injury to the PCF’s blood supply during harvest. The size of the expected defect/s will determine the length and design of the PCF.

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