PÁGINA DEL RESIDENTE

What should the diagnosis and treatment be?

¿Cuál sería su diagnóstico y su manejo terapéutico?

We report the case of a 35 year-old man with no relevant medical history who had undergone surgery 8 years earlier at the Valle Calí University Hospital (Colombia) for frontal meningioma. Surgical and radiological information about the intervention to excise the tumor was unavailable. The patient suffered seizures in the first year after surgery. The patient later received complementary treatment consisting of irradiation, removal of the frontal bone flap, and frontal reconstruction with titanium mesh. After experiencing repeated episodes of frontal cellulitis, he was referred to our department by his reference hospital for definitive surgery and frontal reconstruction.

The texture of the titanium mesh and chronic frontal suppuration were appreciable in the physical examination (Fig. 1). Cranial CT revealed the titanium mesh positioned between the skin and dura mater covering the frontal bone defect (Fig. 2).

In this situation, what therapeutic strategy would you use?

Reconstructive possibilities in surgery of the frontal skull base and cavity. A case report

Posibilidades reconstructivas en cirugía de base-bóveda craneal frontal. A propósito de 1 caso

I. Heras Rincón¹, I. Zubillaga Rodríguez², G. Sánchez-Aniceto², R. Gutiérrez Díaz², J.J. Montalvo Moreno³

1 Médico Residente.
2 Médico Adjunto.
3 Jefe del Servicio de Cirugía Oral y Maxilofacial.
Hospital Universitario 12 de octubre. Madrid, España

Correspondence

Frontal surgery and reconstruction were planned due to the patient’s situation. After CT of the skull and facial massif, the following surgical procedure was performed under general anesthesia with orotracheal intubation: reopening of the previous scar using a coronal approach and removal of the frontal titanium mesh (Fig. 3), which revealed the imprint of the osteosynthetic material on the dura mater (Fig. 4); dissection of superficial temporal vessels to obtain a microvascularized free omental flap (Fig. 5) that was positioned in the cranial fossa after obliterating the dead space (Fig. 6); and completion with end-to-end microanastomosis of the superficial temporal artery and vein to omental vessels (Fig. 7). A Tutopatch was used to repair a dural defect.

The patient was released as a result of his favorable clinical course (Fig. 8) and cranioplasty was deferred. The fundamental problem, which we will examine in greater detail below, is the choice of biomaterial to be used. There is sufficient bibliography on the matter, but no consensus among authors. Eight months later, the patient underwent surgery to reconstruct the frontal bone defect. The skull was reopened again, under general anesthesia with orotracheal intubation, using a coronal approach. Curettage of the frontal sinus mucosa was performed and the sinus was closed with a free residual omental flap and a performed acrylic implant (Fig. 9) (Synthes^®) fixed with four 1.3 mm plates (Synthes^®). Finally, the patient was released with CT follow-up in the reference hospital. The aesthetic and functional result 6 months after cranioplasty was excellent (Figs. 10 and 11).

Discussion

We report a case that was technically complicated and a therapeutic challenge for several reasons. Firstly, a solution to a sequela of neurosurgical resection had to be devised without any knowledge of the tumoral exeresis performed or any report on the intervention, histopathology, or radiography. Secondly, the surgical bed (anterior cranial fossa) had to be isolated from a contaminated area, the paranasal sinuses. Thirdly, the dural defect derived from tumor resection had to be closed, and fourthly and finally, the frontal bone defect had to be reconstructed. In addition, we could not overlook the fact that the patient had been irradiated, which considerably worsens local vascularization and reduces the reconstructive options.

Surgery of the skull base has been revolutionized in the last two decades because of the development of new approaches to this complex anatomical area. Neurosurgeons, handin- hand with the new head and neck surgeons, have changed the parameters of what was once considered «nonresectable.»¹ Increasingly larger defects are being created in the skull base. This revolution, however, would not have been possible without new reconstruction techniques. Recent advances in radiology, microsurgical techniques, and reconstruction have made craniofacial surgery the treatment of choice for tumoral pathology of the anterior cranial fossa.^2-6

Any defect in the skull base that communicates the intracranial content with the nasal cavity or paranasal sinuses must be reconstructed. Traditionally, such defects were covered with layers of nonvascularized tissue (fascia lata or synthetic materials, among others). This can produce necrosis, CSF fistula, and infection, which may have fatal consequences in the form of meningitis or cerebral abscess. The use of vascularized tissue in local or free vascularized flaps has considerably diminished associated morbidity and mortality.⁷

Local flaps, like galea-pericranial aponeurosis or temporal muscle, can be used successfully to close small cranial defects of the anterior cranial fossa. Medium-to-large defects require the use of free flaps, which provide reliable vascularization and more volume, are more adaptable and flexible, better obliterate dead space, and improve the aesthetic outcome. Free flaps must be used imperatively in previously irradiated patients because of the deficient state of their local vascularization.

Surgery of the skull base requires the efforts of a multidisciplinary team. It is essential to properly isolate the central nervous system after resection. Isolation begins with the dura mater. Dural tears must be sutured, if possible. If not possible or in the case of dural defects secondary to resection, the defect must be repaired with an autologous fascia lata graft or with heterologous patches. The dural tissue then must be covered with a well vascularized layer of tissue. Successful repair of the dural defect seems to depend less on the material used than on achieving a truly watertight seal.^8,9 Choice of the free flap to be used depends on several factors, such as the defect size, required pedicle length, and preferences of the surgeon. The local receptor vessels of choice are usually branches of the external carotid artery (especially the occipital artery) and external jugular or internal jugular veins and their branches. The flap can be monitored postoperatively by echo-Doppler or a tube that communicates with the outside. The free flap of choice for many continues to be the rectus abdominis, due to its good vascularization, large volume, and the length and size of the pedicle. Nonetheless, innumerable flaps have been described. We decided to use a free omental flap in our patient because it is adaptable and allows us to obliterate dead space more effectively. This prevents fluid accumulations that can become infected and cause therapeutic failure. Regardless of the free flap used, there is a lower rate of complications than with local flaps, which translates into better healing, a lower rate of meningitis and CSF fistula, and a shorter hospital stay.¹⁰

When we have properly isolated the anterior cranial fossa from the paranasal sinuses, we must reconstruct the frontal bone defect below the free flap.

The main indications for cranioplasty are protection against injury and improved aesthetic outcome.¹¹

Defects greater than 16 cm² must be reconstructed, whereas minor fronto-orbital defects may be reconstructed for aesthetic purposes. The problem in the frontal area is not the indication for reconstruction, but the most appropriate material to be used for reconstruction. A CT made before cranioplasty shows our patient’s frontal defect (Fig. 12).

Since ancient times, many materials have been used to close frontal defects, but even now there is no clear choice. Autologous bone has several disadvantages that restrict its use, such as the morbidity of the donor zone, the limited amount of bone available, and variations in resorption. It is the biomaterial of choice for small defects for many authors. Methylmetacrylate is a good option due to its relatively low cost, availability, and resistance to infection (Manson et al. reported that it was the biomaterial of choice in adults with soft tissues of good quality and no history of infection). ¹² However, it is an inert substance that cannot adapt to changes in the bone (thus limiting its use in children) or promote bone regeneration.

The advantage of hard tissue replacement (HTR) is that it can be custom-fitted for each patient using computerized stereolithographic models. In addition, its porosity and hydrophilic properties promote vascular penetration of the material. Hydroxyapatite paste in the formof ceramics (nonresorbibles) or cement (resorbible) can be used. Hydroxyapatite cement is an excellent biomaterial, but there is still no histological evidence that much bone growth (osseous invasion has only described on the periphery of implants)¹³ or bone resorption occurs in humans in a follow-up period of up to three years. Little bone growth has been observed in animal studies after three years of follow-up.¹⁴ Hydroxyapatite pastes can be used in both adults and children. Its weak point is a predisposition to infection because the material fractures with minimal trauma. This fragility has inspired combinations with titanium mesh affixed by osteosynthesis to the surrounding bone, which acts as scaffolding for the material in total thickness cranial defects.

The ideal characteristics of a material would include: biocompatibility, absence of foreign-body inflammatory response, radiolucency, malleability, nonresorbible, osteoactive, and easily available.

Cranial defects often are the consequence of a tumor resection, as in the case of our patient. One would think that cranioplasty in the first surgical intent would be better for the patient, but this is not so for several reasons. The circumstances of the resection, such as dural defects and communication with contaminated cavities like the paranasal sinuses, may make primary reconstruction inadvisable. Introduction of a foreign body considerably raises the risk of local infection that, aside from being life-threatening for the patient, can spoil any previous reconstructive procedure in the area and make it necessary to remove implants. Closure of the frontal defect also can contribute, together with the immediate postoperative cerebral edema, to raising intracranial pressure. Local infections are a contraindication to cranioplasty. A wait of at least six months and suitable antibiotic treatment is recommended for successful cranioplasty. A six-month wait before reopening a coronal approach is recommended.

As mentioned above, our patient waited eight months after the free omental flap was installed before a preformed acrylic implant that was custom-fitted for the patient with computerized stereolithographic models was positioned and fixed with titanium microplates.

Correspondence:
Dr. Ignacio Heras Rincón
Servicio de Cirugía Oral y Maxilofacial.
Hospital Universitario 12 de octubre.
Avenida de Córdoba s/n, 28041 Madrid, España
Email: nachohr1@hotmail.com

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