Fig. 6.1 (a, b) Principle of the approach. The orbitozygomatic (OZ) approach is performed when the angle of the surgical corridor toward a deep lesion is higher and/or the lesion is deeper and exposure would require significant brain retraction with a pterional or frontolateral approach. By removing parts of the orbital rim, orbital roof, anterior clinoid process, and/or the zygoma, the entry angle is made shallower and less retraction is necessary for exposure of the target, for example, at the upper clivus, perimesencephalic cisterns, or a high-riding basilar bifurcation.
Orbitozygomatic Craniotomy: One Piece or Two Pieces?
Fig. 6.2 (a, b) One-versus two-piece OZ. The craniotomy can be carried out in one piece (a) or in two pieces, when a pterional craniotomy is performed before removal of the orbitozygomatic bar (b). The two-piece OZ gives a better view and is less traumatic, because the dura can be mobilized and the bony cuts can be made under direct visual control.
Fig. 6.3 (a, b) Partial OZ. In many cases, a “full” OZ with removal of the orbital and zygomatic bar is not required. A removal limited to either the orbital (a) or the zygomatic bar (b), depending on the surgical target, in addition to the pterional craniotomy, may offer the same advantages.Fig. 6.4 (a, b) The two-piece orbitozygomatic approach. The head is turned 20–60° (most often 30–45°), depending on the surgical target, and tilted toward the floor to place the zygoma at the highest point.Fig. 6.5 (a, b) Landmarks and skin incision. For sufficient exposure of the orbital rim, the zygoma, and the zygomatic arch, the skin incision has to cross the midline about 2–5 cm and has to extend 1 cm caudal to the zygomatic arch, which is sufficient to expose the arch for the bony cut. The critical distance to the main trunks of the facial nerve is about 1.5 cm, and should be always respected. The following landmarks are useful: nasion (1), supraorbital foramen (2), frontotemporale (3), frontozygomatic suture, which can be palpated (4), zygoma (5), and zygomatic arch (6).Fig. 6.6 (a–c) Initial skin flap preparation. After skin incision and placement of the scalp clips, an interfascial (b) or subfascial (c) dissection is performed (see Chapter 5.2.1, “Facial Nerve Anatomy and Protection,” Fig. 5.19b, c) to remain underneath the branches of the facial nerve. Creating a combined musculocutaneous flap, as with the pterional craniotomy, is not possible because the orbital bar, the zygoma, and the zygomatic arch have to be exposed.Fig. 6.7 (a, b) Detachment of the temporalis fascia from the orbital rim and zygoma. The deep layer of the temporalis fascia is followed to the attachment at the orbital rim and the zygoma. Both the deep and the superficial layer of the temporalis fascia attach to the orbital rim and the zygoma. This attachment is detached and these layers are lifted toward the galea to expose the orbital rim and/or the zygoma (zy) using fish hooks.Fig. 6.8 (a, b) Detachment of the temporalis muscle. The muscle is cut from the superior temporal line leaving a 1-cm cuff for resuturing the muscle at the end of surgery. This improves cosmesis by preventing the muscle from slipping down or retracting. This maneuver is not necessary when a combined musculocutaneous flap is lifted during a pterional craniotomy. The superficial and the deep temporal fascia are detached from the orbital rim and the zygoma and these structures are exposed.Fig. 6.9 (a, b) Detachment of the periorbita. The periorbita is detached from the intraorbital bone to prepare for the bone cuts. Usually, the detachment extends from the medial edge of the planned craniotomy to the base of the lateral orbital bar, i.e., beyond the frontozygomatic suture until the inferior orbital fissure can be palpated from the inside of the orbit. If the supraorbital nerve is fixed in a supraorbital foramen, the foramen is opened under the microscope using a chisel or a 2–3-mm drill.Fig. 6.10 (a, b) Pterional craniotomy and detachment of the dura. A classical pterional craniotomy is performed. The dura is detached frontally and around the sphenoid wing to prepare for the OZ cuts.
Fig. 6.11 (a, b) Planning of the orbitozygomatic bone cuts. The cuts are performed using an oscillating saw. We prefer to start at the zygomatic arch, but this may be up to the preference of the surgeon.The cuts will be explained in the following figures (▶Fig. 6.12, ▶Fig. 6.13, ▶Fig. 6.14, ▶Fig. 6.15, ▶Fig. 6.16, and ▶Fig. 6.17).Fig. 6.12 (a, b) Cut 1: zygomatic arch. The masseter muscle is detached from the inferior border of the zygomatic arch. The cut at the zygomatic arch is made at the posterior end in a slightly oblique direction. The idea is to lock the arch into this configuration when the masseter pulls the arch downward after surgery.Fig. 6.13 (a, b) Cut 2: the zygoma. The second cut is performed across the zygoma starting at the lateral border below the zygomatic arch and directed toward the inferior orbital fissure, which has already been located by intraorbital palpation. The cut stops in the middle of the zygoma.Fig. 6.14 (a, b) Cut 3: completing the cut of the zygoma. The inferior orbital fissure is palpated from intraorbital and the oscillating saw is inserted. The cut of the zygoma is now completed from a medial to lateral direction.Fig. 6.15 (a, b) Cut 4: orbital roof. The periorbita is detached further toward the upper and lateral edge of the superior orbital fissure. A pad is placed between the periorbita and the bone to protect the periorbita. The dura is also detached and the cut is performed at the medial border of the craniotomy, approximately at the level of the supraorbital foramen toward the upper and lateral edge of the superior orbital fissure.Fig. 6.16 (a, b) Cut 5: inferior sphenoidal cut. The lateral end of the inferior orbital fissure is palpated from outside in the infratemporal fossa and the oscillating saw is inserted. The cut is directed slightly posteriorly to reach the middle fossa approximately 1 cm below the sphenoid ridge. The cut is performed from the outside to the inside. The detached dura is retracted to visualize the entry of the tip of the saw into the middle fossa. It cuts the outer part of the sphenoid in the middle fossa, but not the inner part.Fig. 6.17 (a, b) Cut 6: superior sphenoidal cut. The final cut divides the inner part of the sphenoid and completes the orbitozygomatic osteotomy. The dura is further detached around the sphenoid wing and the superior lateral edge of the superior orbital fissure is palpated. The line of the previous inferior sphenoidal cut (cut 5) is localized in the middle fossa and the tip of the oscillating saw is inserted. The cut is directed superiorly to the lateral edge of the superior orbital fissure. Care should be taken to use only the tip of the saw to make the cut and to direct it toward the superior and lateral bony end of the fissure, and not into the fissure. The cut connects the osteotomy lines from cut 5 and cut 4 at the lateral edge of the superior orbital fissure or close to it.Fig. 6.18 (a, b) Removal of the orbitozygomatic bar. Sometimes the OZ bar is still connected to a small island of bone, but can usually be fractured and then detached from the soft tissue and removed. The view from anterior (b, left) and superior (b, right). lo, lateral orbital wall; or, orbital roof; so, superior orbital wall; za, zygomatic arch; zy, zygoma.Fig. 6.19 (a, b) Surgical site after orbitozygomatic craniotomy. The angle of the intradural approach is now shallower than with a frontolateral or pterional craniotomy.Fig. 6.20 (a, b) Closure and fixation with mini-plates. First, the orbitozygomatic flap is refixed, followed by the pterional flap.Fig. 6.21 (a, b) The muscle is sutured to the cuff at the pterional bone flap and the temporalis fascia posteriorly. The galea and skin are closed in the usual fashion.
Checklist
Position the head so that the zygoma is the highest point.
The skin incision must be large enough to expose the zygoma and the zygomatic arch. It has to cross the midline and reach down to 1 cm below the zygomatic arch. Do not go further down; be aware of the facial nerve as it exits the parotid gland.
Perform interfascial or subfascial dissection of the temporalis muscle.
Detach the temporalis fascia from the orbital rim and the zygoma and expose the zygoma to see a continuous bony surface from the zygoma to the zygomatic arch.
Leave a fascia muscle cuff to facilitate refixation of the temporalis muscle.
Carefully detach the periorbita.
Perform the cuts as described.
Place a cotton pad between the periorbita and the orbital roof before performing cut 4.
Despite cut 6, the bone fragment may still not be entirely mobile. However, slight elevation should crack the final bony bridge. There may still be soft tissue attaching to the bone fragment, which should be detached carefully.
Further Readings
Lemole GM Jr, Henn JS, Zabramski JM, Spetzler RF. Modifications to the orbitozygomatic approach. Technical note. J Neurosurg 2003;99(5):924–930Youssef AS, Willard L, Downes A, et al. The frontotemporal-orbitozygomatic approach: reconstructive technique and outcome. Acta Neurochir (Wien) 2012;154(7):1275–1283Zabramski JM, Kiriş T, Sankhla SK, Cabiol J, Spetzler RF. Orbitozygomatic craniotomy. Technical note. J Neurosurg 1998;89(2):336–341
Fig. 6.22 (a, b) Positioning. The transorbital approach is used for midline and parasellar lesions including aneurysms of the anterior communicating artery complex. The head is positioned at an angle of 30–45° toward the contralateral side and hyperextension of 15°. The lateral aspect of the orbital rim is considered as the highest point.Fig. 6.23 (a, b) Anatomy overview. The left image shows the planned skin incision. The hair has been shaved and the incision is located behind the hairline. Important landmarks are: (1) the supraorbital foramen, (2) the posterior lateral edge of the zygomatic process of the frontal bone indicating the cranial base, (3) the frontozygomatic suture as the landmark for the sphenoid ridge, (4) the frontal branch of the superficial temporal artery, (5) the fascia of the temporal muscle connecting to the superior temporal line, and the nasion (6). For planning the length of the skin incision, the upper part of the zygomatic process and the nasion to determine the midline should be located by palpation.Fig. 6.24 (a, b) Draped position before skin incision. The skin incision is similar to the pterional approach, but, first, it does not extend as far inferior on the temporal side and, second, it should extend beyond the midline to facilitate exposure of the supraorbital foramen, which serves as the landmark for the medial burr hole. Later, it also facilitates intraorbital preparation. The skin incision should be made behind the hairline for cosmesis. We still prefer a frontotemporal hairline incision, although the eyebrow incision may be an acceptable alternative for bald patients.Fig. 6.25 (a, b) Flap preparation. After a cautious incision of the skin and the galea, the superficial temporal artery is identified within the temporal fascia. The frontal or parietal branch of the artery is divided if necessary (see Chapter 6.1.2, Full OZ or Partial OZ). In the case of arterial injury, a small hemoclip is recommended to secure the proximal stump to prevent rebleeding. The temporalis muscle is left intact. The flap is developed anteriorly until the yellow fat pad of the temporal muscle becomes visible.This yellow appearance of the temporal muscle fascia is caused by the interfascial temporal fat pad that contains the frontal branch of the facial nerve. After reaching the yellow fat pad, the temporal fascia is incised and dissection is continued anteriorly in the interfascial or subfascial plane (see Chapter 6.1.2, Full OZ or Partial OZ). This step protects the frontal branch of the facial nerve from stretching or injury. The superior temporal line is identified by the attachment of the temporal muscle fascia. The interfascial fat pad must be left at and mobilized together with the scalp flap to prevent injury to the frontal branch of the facial nerve. The scalp flap is retracted basally with the help of galea hooks. Because of the danger of traction to the frontal branch of the facial nerve, it is important to avoid deep insertion of galea hooks on the temporal side.Fig. 6.26 (a, b) Subperiosteal elevation of the anterior part of the temporalis muscle and dissection of the periorbita. The anterior attachment of the temporal muscle at the orbital pillar and the anterior aspect of the linea temporalis are incised sharply. The temporal muscle is then dissected from the underlying bone and pulled back with the help of a galea hook. The temporal muscle should not be mobilized more than necessary for the limited craniotomy. The lateral and superior orbital rims are then dissected from the periorbita using a blunt curved dissector. At this stage, attention should be paid to the frontal nerve as it turns around the orbital rim at the medial aspect of the planned craniotomy. Occasionally, it may be necessary to mobilize the frontal nerve out of its bony groove or tunnel. Three fishhooks are used to gently pull the detached flap inferiorly; a suture retracts the anterior temporal muscle laterally and downward for positioning the keyhole burr hole.Fig. 6.27 (a, b) Craniotomy planning. A drawing anticipates the planned craniotomy. The lateral extension is toward the sphenoid ridge (i.e., the sylvian fissure); medially the extension should end above the trigeminal nerve root. We recommend two burr holes for the craniotomy. The initial burr hole corresponds to the keyhole of the pterional craniotomy placed at the frontozygomatic suture. The direction of drilling, however, aims more toward the orbit so that the orbit and the anterior cranial fossa are opened simultaneously. If some bone remains on the frontal or the orbital side, use of a diamond drill may become necessary. The second burr hole is made at the medial aspect of the planned craniotomy, immediately above the orbital rim. The dura is separated from the convexity and from the orbital roof through these burr holes using a blunt dissector.Fig. 6.28 (a, b) Craniotomy. The two burr holes are then connected with the craniotome along the upper delineation of the planned opening. Note that there is no craniotomy planned between the burr holes at the level of the orbit, i.e., the basal part. The superior and lateral orbital rims are best cut using a small bone saw or the craniotome. The dura and the periorbita must be protected with a small spatula. The bone cut in the lateral orbital rim is extended down to the lateral burr hole. With a small punch, starting from the lateral burr hole, the orbital roof is divided along the pterion to a depth of 3 to 4 cm. The anterior aspect of the medial orbital roof is divided through the medial burr hole, again using a small punch or a diamond drill.Fig. 6.29 (a, b) One-piece orbitocraniotomy with fracturing of the orbital roof. The bone flap is then elevated and the posterior orbital roof is fractured between the lateral and medial orbital roof incision. Care should be taken to fracture the orbital roof as far back as possible. We do not advocate removal of residual orbital roof in an osteoclastic manner. If this is done, the orbital roof must be reconstructed later with foreign material to prevent orbital roof instability with enophthalmos or pulsating exophthalmos. The dura is opened in a basally pediculated curvilinear fashion. The dural opening does not cross the sylvian fissure.Fig. 6.30 (a, b) Dura closure and bone refixation. The dura is closed so that it is watertight. The periorbita is sometimes injured during dissection from the orbital roof. To prevent protrusion of the orbital fat, periorbital tears should be repaired immediately with a suture. If the frontal sinus has been opened at the medial aspect of the orbitocraniotomy, the defect is plugged with a muscle graft taken from the temporal muscle. We do not recommend a pediculated pericranium flap in this location, because of the risk that it may interfere with eyebrow motility. The bone flap is replaced and attached with rivets or microplates. Burr holes can be closed using Palacos bone cement, miniplates, or titanium mesh. The anterior aspect of the temporalis muscle is reattached at the linea temporalis and the skin flap is closed stepwise.
Checklist
The head is positioned to have the lateral aspect of the orbital rim as the highest point.
The upper part of the zygomatic process and the nasion to determine the midline should be located by palpation for later skin incision.
The temporal fascia is incised and dissection is continued anteriorly in the interfascial or subfascial plane.
The lateral extension of preparation is the sphenoid ridge, and the medial extension is the supraorbital foramen.
The initial burr hole corresponds to the keyhole; the second burr hole is made above the orbital rim and then connected with the craniotome along the upper delineation.
The superior and lateral orbital rims are cut, and the bone cut in the lateral orbital rim is extended.
The bone flap is then elevated and the posterior orbital roof is fractured between the lateral and medial orbital roof incision.
The dura is opened in a basally pediculated curvilinear fashion.
Meticulous closure of bone, muscle, and skin is necessary.
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