9 Approaches to the Orbita

10.1055/b-0039-169402

9 Approaches to the Orbita

9.1 Frontolateral Approach to the Orbit

Torstein R. Meling

A frontolateral craniotomy can be combined with a superior orbitotomy to give wide superior and lateral exposure of the orbital contents for microsurgical removal of orbital tumors. It is particularly suitable for large orbital neoplasms, tumors in the orbital apex, optic canal lesions, lesions with intracranial extensions, and medial orbital tumors (see ▶Fig. 9.1, ▶Fig. 9.2, ▶Fig. 9.3, ▶Fig. 9.4, ▶Fig. 9.5, ▶Fig. 9.6, ▶Fig. 9.7, ▶Fig. 9.8, ▶Fig. 9.9, ▶Fig. 9.10, ▶Fig. 9.11, ▶Fig. 9.12, ▶Fig. 9.13, and ▶Fig. 9.14).

**Fig. 9.1 (a, b) Positioning.** The patient is placed in the supine position with the body slightly elevated. The head is fixed in a three-pin headrest and elevated above the level of the heart. The head is rotated 15–20° to the contralateral side and tilted laterally to increase the surgeon’s working space. The head is then retroflexed 15° so that gravity causes the frontal lobe to fall away from the anterior cranial fossa and allow for retractor-free intracranial dissection.

**Fig. 9.2 (a, b) Skin incision.** The skin is minimally shaved and infiltrated using 1% Xylocaine with 1:200,000 adrenaline. Using a No. 20 knife blade, a slightly curved frontotemporal skin incision is made behind the hairline. The incision stops 2 cm from the midline and 3 cm above the zygoma. Hemostatic clips are placed on the margins of the incision.

**Fig. 9.3 (a, b) Skin flap.** The skin flap is retracted anteriorly using three or four small fishhooks with elastic bands. The temporal muscle is left in place. To avoid injury to the supraorbital nerve, the superior orbital margin should not be exposed.

**Fig. 9.4 (a, b) Detachment of the temporal muscle.** Superiorly, the temporal muscle is detached along the muscle insertion. The temporalis muscle is also detached from its insertion at the zygomatic process of the frontal bone and the temporal fossa and retracted inferiorly toward the zygomatic arch with one or two fishhooks. It is lifted up rather than retracted by force.

**Fig. 9.5 (a, b) Burr hole.** Using a 2-mm, sharp burr, a small burr hole (3–5 mm) is made in the frontal bone, just posterior to the zygomatic process and caudal to the superior temporal line, so as to be covered by the temporalis muscle when this is later reattached.

**Fig. 9.6 (a, b) Bone flap.** Using a high-speed electric craniotome, a lateral frontotemporal craniotomy is performed. A straight anterior cut is made as close to the superior orbital rim as possible in a lateral-to-medial direction, avoiding the lateral border of the frontal paranasal sinus as measured on preoperative MR scans. Next, a C-shaped line is cut from the burr hole to the medial border of the previously made frontobasal line. The size of the bone flap depends on whether the intraorbital lesion is medial or lateral to the levator muscle, with the medial location requiring a wider exposure. As the most common intraorbital corridor is between the levator and lateral rectus muscles, the almost superelliptic bone flap is usually 5 cm wide (coronal plane) and 2.5 cm deep (sagittal plane).

**Fig. 9.7 (a, b) Additional bone drilling.** The inner edge of the orbital bar is drilled away expanding the view along the skull base.

**Fig. 9.8 (a, b) Extradural dissection.** The dura is lifted off the inner table of the frontal bone and the orbital roof. Care is taken not to come too far medially, so as not to injure the ipsilateral olfactory nerve in the olfactory groove. No lumbar drain is inserted, as head elevation and good neuroanesthesia are sufficient for brain relaxation. Lesions confined entirely to the orbit can be removed without opening the dura, whereas intradural exposure is required for those lesions involving the intracranial segment of the optic nerve.

**Fig. 9.9 (a, b) Superior orbitotomy, visualization of the periorbita, and underlying anatomy of the orbit.** Using a Misonix electric 1-mm bone scalpel, straight cuts are made in the superior orbital roof, creating a trapezoid bone flap. The bone flap can be supplemented by a craniectomy over the optic canal if the most posterior parts of the orbit and the intracanalicular segment of the optic nerve need to be exposed. Care should be taken not to injure the underlying periorbita and the trochlear and frontal nerves in the midline and the lacrimal nerve laterally. The periorbita is frequently thinned by the raised intraorbital pressure caused by the lesion and is often very difficult to preserve.

**Fig. 9.10 (a, b) Periorbital dissection.** The periorbita is incised using a diamond knife or microscissors. A V-shaped incision is made and the periorbita flap is retracted anteriorly. This exposes the trochlear nerve and the supraorbital and supratrochlear branches of the frontal nerve, all of which run immediately beneath and can often be seen through the periorbita. The trochlear nerve passes medially above the levator muscle to reach the superior oblique muscle. The frontal nerve is a branch of the ophthalmic nerve (V1) and passes through the superior orbital fissure to course superiorly on the levator muscle. It divides into a supratrochlear nerve, which passes above the trochlea of the superior oblique muscle, and the supraorbital nerve, which passes through the supraorbital foramen or notch in the supraorbital margin. The lacrimal nerve passes above the lateral rectus muscle to innervate the lacrimal gland and convey sensation to the area around the lateral part of the supraorbital margin.

**Fig. 9.11 (a, b) Closure.** After the resection, any bleeding is controlled by applying FloSeal hemostatic matrix rather than bipolar diathermy. A small piece of Tachosil is placed over the intraorbital fat to reconstruct the periorbita. To avoid a pulsating exophthalmos, the orbital bone flap is replaced and fixed with 1-mm titanium mini-plates.

**Fig. 9.12 (a, b) Bone closure.** The craniotomy bone flap is replaced and secured using 1-mm titanium mini-plates. Care is taken to ensure that the bone flap is level with the surrounding cranium. The muscle is reattached to the cuff.

**Fig. 9.13 (a, b) Bone closure.** Any irregularities or larger gaps can be filled using BoneSource hydroxyapatite cement.

**Fig. 9.14 (a, b) Skin closure.** The pericranium is closed with a running Monocryl 3–0 suture. The skin is closed using skin sutures. The wound is dressed using 3M Steri-Strips.

Checklist

Look at CT and MR images to familiarize yourself with the frontal sinus anatomy. Cave: very lateral extensions.
Before skin incision, make sure the head is retroflexed enough to allow the frontal lobe to fall away from the anterior cranial fossa and enable retractor-free intracranial dissection.
Make the skin incision > 1 cm behind the hairline and ensure that it is sufficiently large.
When performing the interfascial dissection, stay directly on the superficial layer of the deep temporal fascia at all times to avoid injury to the temporal branch of the facial nerve.
Detach the temporalis muscle from its anterior insertion and retract it inferiorly toward the zygomatic arch.
Use neuronavigation to identify the lateral border of the frontal sinus.
Make a small burr hole posterior to the zygomatic process of the frontal bone and caudal to the superior temporal line to improve cosmesis.
Make the first cut straight and run it as close to the superior orbital rim as possible in a lateral-to-medial direction. Cave: very medial cuts can injure the supraorbital nerve if not properly detached from its canal/groove.
Make the last cut C-shaped, starting from the burr hole and running to the medial border of the first cut.
Drill the tabula interna of the orbital bar to expand the field of view while leaving the tabula externa intact for cosmesis.
When lifting the dura off the frontal bone and the orbital roof, be careful not to go too far medially, so as not to injure the ipsilateral olfactory nerve in the olfactory groove.
Use a Misonix electric 1-mm bone scalpel or a pediatric craniotome to make the cuts in the superior orbital roof so as to avoid losing too much bone.
After opening the periorbita, identify the trochlear nerve and the supraorbital and supratrochlear branches of the frontal nerve as landmarks.
For the intraorbital part of surgery, retract the rectus muscles gently using PDS 5–0 traction sutures.
Gently dissect the intraorbital fat lobules using cotton swaps as blunt dissectors to avoid rupture of the lobules.
Avoid bipolar electrocoagulation or, if unavoidable, use at a very low power setting. Try to stop bleeding with FloSeal hemostatic matrix rather than bipolar diathermy.
To avoid a pulsating exophthalmus, fix the orbital bone flap with Lorentz 1-mm titanium mini-plates or PDS sutures.
Ensure that the bone flap is level with the surrounding cranium so as to avoid any irregularities and use hydroxyapatite cement to fill any larger gaps.