28 Cranio-Orbit-Zygomatic (COZ) Approach
Abstract
With the goal of minimizing surgical complications caused by brain retraction, several variations of the traditional craniotomies were developed. The cranio-orbit-zygomatic (COZ) approach was assembled by adding orbital and zygomatic osteotomies to a standard frontotemporal approach. Mobilizing the zygomatic arch and removing the orbital rim allow both vertical and horizontal widening of the surgical field without disturbing the neurovascular structures. The advantage of this approach is to provide multiple routes as obtained with the pterional, transbasal, transsylvian, pretemporal, and subtemporal approaches. The surgical technique is relatively simple requiring a single cranial bone flap.
Keywords: cranio-orbit-zygomatic, COZ, skull base, middle fossa, brain tumor
28.1 Background
Despite the advances in microsurgical techniques and neuroanesthesia, the greater neurosurgical complications come from brain retraction; therefore, the criteria when selecting a neurosurgical approach is to achieve maximum exposure with minimum retraction over neural tissue.1 , 2 Since the description of orbital removal for pituitary lesions through a frontal approach by McArthur in 1912 and Frazier in 1913, orbital osteotomy became an important maneuver to increase exposure of the structures at the base of the skull.1 , 3 , 4 Yasargil and Fox, in 1975, used a frontal approach associate with orbital osteotomy to treat anterior communicating artery aneurisms with superior extension.5 Later, Jane et al used a supraorbital approach for vascular lesions located at the anterior skull base and orbit, which is currently used for complex aneurism in the anterior communicating segment and tumors located in the anterior skull base and sphenoid wing.1 , 6 , 7 Al-Mefty then modified this approach in order to associate a pterional approach with the removal of the superior and lateral orbital rims in a single piece.3 Removing the orbital rim increases the horizontal angle of exposure, especially when using a subfrontal or transylvian approach. Additionally, the mobilization of the zygomatic arch allows wider elevation of the temporal muscle, increasing the vertical angle of view and the possibility to access the lower temporal, infratemporal, and sphenopalatine fossae.2
28.2 Indications
The cranio-orbit-zygomatic (COZ) approach is indicated for patients harboring lesions located in the anterior, middle, and upper-third of the posterior fossae. It is an excellent choice for large lesions located in the suprasellar, parasellar, and retrosellar areas, or extending into the cavernous sinus and the orbit, for primary lesions in the cavernous sinus (tumors, aneurysms, and fistulas), and tumors in the interpeduncular fossa and upper clivus.8 , 9
28.3 Technique
28.3.1 Positioning
The patient is placed in supine position and cushions are placed under the ipsilateral shoulder. The head is fixed on a three-point headrest, elevated and deflected, and rotated as needed to the opposite side. The abdomen and thigh should be prepared for possible fat and fascia lata harvest, respectively (Fig. 28.1).
Fig. 28.1Patient positioning: (a) The head is rotated according to each case, (b) elevated and deflected. (c) The thigh is prepared for fascia lata harvest.
28.3.2 Skin Incision and Pericranial Flap
The skin incision starts 1 cm anterior to the tragus at the level of the posterior root of the zygoma, runs slightly posterior just above the pinna, and then curves forward, toward the contralateral side. The superficial temporal artery (STA) is carefully identified and its anterior branch can be cut and elevated with the skin flap, which is mobilized anteriorly. The contralateral and posterior extensions of the skin incision will mostly depend on the amount of pericranium needed for reconstruction (Fig. 28.2). A sharp dissection is carried out to preserve the integrity of the pericranium. The pericranium can then be excised as posterior and medial as needed, keeping a large and vascularized pedicle at its frontal portion (Fig. 28.3 and Fig. 28.4).
Fig. 28.2Skin incision (a) beginning 1 cm anterior to the tragus (T), just superior to the zygoma (red dashed lines) and running posterior (yellow arrows) before (b) crossing the midline (red dashed line). (c) Depending on the amount of pericranium needed the incision might run more posterior (yellow arrows) and (d) involve more of the contralateral side (cadaveric demonstration).
Fig. 28.3 (a) Subcutaneous tissue dissection preserving the pericranium (P) and the temporal muscle (TM). (b) Pericranial flap (P) elevated with a vascularized pedicle (arrows). (c) When incision runs more posterior it is possible to harvest a (d) wider area of pericranium.
28.3.3 Subfascial Dissection
In order to prevent injuries to the frontotemporal branches of the facial nerve, a straight cut is made in the superficial and deep layers of the superficial fascia of the temporal muscle, from the posterior root of the zygoma to the frontozygomatic suture, exposing the muscle fibers10 ( Fig. 28.5a).
Fig. 28.4Anatomical demonstration. (a) Skin is reflected anteriorly. A subfascial dissection of fat pad to preserve frontalis branch of facial nerve is demonstrated. (b) Harvested pericranium flap displaced anteriorly exposing underlying bone. (c) Temporalis muscle mobilized inferiorly and demonstration of craniotomy encompassing part of orbit. Temp. Musc., temporalis muscle.
28.3.4 Zygomatic Osteotomy
The zygoma is exposed through a subperiosteal dissection ( Fig. 28.5b). The osteotomy is performed with oblique convergent cuts made in the most anterior and most posterior parts of the arch, which then is displaced downward. Lately, we have been placing the miniplates on the zygoma before cutting it to facilitate reconstruction ( Fig. 28.5c). It is important to notice that the zygoma is not removed but mobilized inferiorly while kept attached to the masseteric muscle ( Fig. 28.5d).
