Orbitozygomatic Infratemporal Approach to Parasellar Meningiomas

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Chapter 53 Orbitozygomatic Infratemporal Approach to Parasellar Meningiomas

Lesions located high in the parasellar region and the interpeduncular fossa are challenging and often difficult to approach, as a result of both the deep position and the surrounding vital structures that obscure the view. In 1977, we developed a new surgical approach, the orbitozygomatic infratemporal approach,1 consisting of an orbitozygomatic osteotomy, a fronto-temporo-orbital craniotomy, and removal of the posterolateral wall of the orbital bone and major sphenoid wing lateral to the foramen spinosum. This approach provides a good exposure of the infratemporal fossa, permits access obliquely upward to the parasellar region and the interpeduncular fossa, and permits safe manipulation of parasellar and interpeduncular lesions via the shortest distance.24

Operative Technique

The patient is placed in the supine position with the thorax elevated 30 degrees to facilitate venous drainage. By using a three-pin head-holder, the head is rotated to the side opposite the lesion without creating excessive torsion of the neck, so that the right pterion is the highest in the surgical field.

A bicoronal scalp incision is made to gain sufficient exposure of the zygomatic arch and superior and lateral orbital margins, starting at the inferior end of the base of the earlobe, running along the anterior margin of the ear cartilage, extending upward and forward, and running within the hairline to a level 3 cm above the upper margin of the contralateral zygomatic arch. The superficial layer of deep temporal fascia is incised and reflected with the skin flap to avoid the injury of the frontal branch of the facial nerve. The skin flap is reflected farther anteriorly with the frontal pericranium to expose the orbitozygomatic complex, cutting the supraorbital notch for the preservation of the right supraorbital nerve.5,6 To preserve the temporal and zygomatic branches of the facial nerve, the fascia covering the temporomandibular joint capsule is carefully pulled away, and the periosteum covering the outer surface of the zygomatic arch is incised vertically just in front of the tuberculum articulare. The entire outer surface of the zygomatic arch from its frontal process to its-pedicle is then fully exposed subperiosteally. The superior and lateral orbital margins are then exposed, maintaining continuity of the pericranium and the periorbita. The superior and lateral periorbita are separated from the superior and lateral posterior walls of the orbit.

Multiple burr holes are made, the first of which, in the lateral frontal bone just behind the frontal process of the zygomatic bone, is the key burr hole. The second burr hole is at the pterion, the third in the temporal bone just above the pedicle of the zygomatic process, the fourth in the squamous suture about 3 cm above the zygomatic arch, the fifth in the coronal suture about 6 cm above the zygomatic arch, and the sixth in the frontal bone 3 cm above the orbital ridge (Fig. 53-1). The anterior and posterior ends of the zygomatic arch are then cut using a sagittal saw, and it is retracted downward hinged on the masseter muscle.

The second, third, fourth, fifth, and sixth burr holes are then connected with a craniotome (see Fig. 53-1). Using a reciprocating saw, osteotomy of the lateral and superior walls of the orbit is performed from the inferior orbital fissure. The orbital content is protected by a spatula during this osteotomy. The frontotemporal bone flap and the orbitozygomatic flap are kept in saline solution containing an antibiotic. While protecting the periorbita and the dura mater with self-retaining retractors with spatulas, the remaining major sphenoid wing lateral to the foramen spinosum, forming the posterolateral orbital wall and the anterolateral part of the middle fossa, and the posterior portion of the orbital roof lateral to the superior orbital fissure, are divided, using either a sagittal saw or small chisel (see Fig. 53-1). The remaining medial part of the minor sphenoid wing is then partially removed with an air drill and a bone rongeur. The bone fragments are kept in the saline solution to be replaced at the end of the procedure.

The exposed frontotemporal dura mater is opened in semicircular fashion, from the medial superior orbital margin to the midportion of the inferior temporal region. Alternatively, in a combined orbitozygomatic epidural and subdural approach,79 an inverted T-shaped dural incision is made along the sylvian fissure to the superior surface of the optic nerve sheath forward with a short vertical incision at the distal sylvian fissure. The orbital contents are retracted medially downward by retracting the anterior dural fringe forward.

The operative microscope is now introduced, and either a trans-sylvian approach or a subtemporal approach can be taken with minimal retraction of the brain. In the trans-sylvian approach, the sylvian fissure is widely opened, with preservation of the bridging veins coming from the tip of the temporal lobe. The parasellar region as well as the interpeduncular fossa can be reached at a short distance through the space formed via this approach.

When the tumor is invading the cavernous sinus (CS),5 the CS is explored by a combined orbitozygomatic infratemporal epidural and subdural approach, which has been described elsewhere.79 The periosteal reflection, which is continuous with the periorbita, is divided at the superior and inferior margins of the superior orbital fissure by sharp dissection using either microscissors or a knife; then the temporal dura propria, forming the superficial layer of the CS, can be separated from the content of the superior orbital fissure (Fig. 53-2A). The lateral part of the anterior clinoid process is shelled out, leaving a thin layer of its cortical bone. The optic canal is then opened along its length. The cortical bone of the anterior clinoid process and the optic strut are removed by a bone-cutting forceps and a small diamond drill (Fig. 53-2B). The dural incision passes along the sylvian fissure to the superior surface of the optic nerve sheath forward, and then turns laterally at a right angle (Fig. 53-2C). It passes backward at a right angle and runs along the medial part of the distal carotid ring, then along the carotid artery 2 mm away from the artery (Fig. 53-2D). Opening of the medial triangle (Hakuba’s triangle, which is a triangle in the subdural space) starts from the distal ring along the medial side of the triangle to the posterior clinoid process and turns laterally at a right angle along the posterior side of this triangle to the dural entrance of the third cranial nerve. The lateral dural fringe of the medial triangle is elevated. Then the remaining outer layer of the CS is separated farther backward from the inner layer of the lateral wall of the CS consisting of the nerve sheaths of the third through fifth cranial nerves (Fig. 53-2E), and the entire CS is unveiled (Fig. 53-2F). Bleeding from the CS is easily controlled by elevating the head side of the table, and the opened venous pathway in the CS is immediately sealed off by insertion of either a fibrinogen-soaked oxidized cellulose sponge or a collagen sponge into the CS, and a bipolar coagulation. Because the intracavernous internal carotid artery (ICA) has its own dural sheath,10 the plane between the ICA and the tumor is usually found relatively easily, and the tumor is freed from the ICA if it is not invasive. When the artery is torn during dissection, 8-0 monofilament nylon interrupted sutures are applied while trapping this segment of the artery between two temporary clips at both C3 and either C5 or the intrapetrous portions of the ICA, with intravenous administration of barbiturates for brain protection8 (pentobarbital 4 mg/kg as the initial dose, followed by 2 mg/kg/hr).