Microscopic Versus Endoscopic Approaches for Craniopharyngiomas

Choosing the Optimal Surgical Corridor for Maximizing Extent of Resection and Complication Avoidance Using a Personalized, Tailored Approach

James K. Liu, MD; Ilesha A. Sevak, BA; Peter W. Carmel, MD; Jean Anderson Eloy, MD

Disclosures

Neurosurg Focus. 2016;41(6):e5 

In This Article

Anterolateral Transcranial Approaches

The anterolateral transcranial approaches expose the suprasellar region via an anterolateral trajectory, usually through a transsylvian or unilateral subfrontal corridor. These generally include the pterional (frontotemporal), orbitozygomatic, and lateral supraorbital (frontolateral) approaches.[20,24,46,59] While all of these approaches typically use a curvilinear incision behind the hairline, the latter group of supraorbital approaches can also be performed with smaller eyebrow or eyelid incisions.[15,21,50,57] These are familiar approaches that provide a short route to the suprasellar region and are particularly useful for tumors that exhibit lateral extension into the sylvian fissure. Recently, Gerganov et al.[24] reported excellent outcomes with an 87% rate of gross-total resection of extensive craniopharyngiomas using a more simple frontolateral craniotomy. While there are a variety of anterolateral approaches, we prefer the one-piece modified orbitozygomatic approach. This approach is a natural extension of the pterional approach which provides a more basal (inferior-to-superior) surgical trajectory, increases the corridor of exposure, shortens the distance to the target, and improves surgical freedom (maneuverability of instruments) while minimizing brain retraction.

Modified One-piece Orbitozygomatic Approach: Technical Pearls and Clinical Case Correlate

With the patient in the supine position, the head is rotated approximately 30° to 45° to the contralateral side with slight extension of the neck so that the malar eminence is at the highest point to facilitate relaxation of the frontal lobes away from the skull base. A curvilinear frontotemporal incision is made behind the hairline, and the scalp is elevated in a 2-layer fashion. The galeocutaneous layer is initially elevated followed by elevation of a vascularized pedicled pericranial flap. Interfascial dissection of the temporalis muscle is performed to protect the frontotemporal branch of the facial nerve. The temporalis muscle is mobilized inferiorly toward the zygomatic arch, leaving a myofascial cuff at the superior temporal line for reattachment at the time of closure. At this juncture, a variety of different craniotomies can be performed (pterional, orbitozygomatic, or supraorbital) depending on the surgeon's choice.

We prefer a one-piece modified orbitozygomatic craniotomy that involves a frontotemporal pterional bone flap that incorporates the orbital rim and a small portion of the zygoma (Fig. 1).[25] This technique allows for a more simplified and efficient cosmetic closure with only a single bone flap to reconstruct without having to plate separate orbital osteotomy fragments. To facilitate the one-piece technique, it is paramount to create a generous MacCarty bur hole that exposes 3 components: 1) frontal lobe dura, 2) orbital roof, and 3) periorbita).[3] The orbital rim is disarticulated with the frontotemporal bone flap as one piece using an osteotome and fracture technique. An orbital osteotomy is made just lateral to the supraorbital notch, inferior to the frontozygomatic suture, and across the orbital roof through the MacCarty bur hole. To maximize pretemporal and transsylvian exposure, we drill off the sphenoid wing down to the superior and lateral walls of the orbit toward the orbital apex at the level of the meningo-orbital band. After opening the dura, wide splitting of the sylvian fissure and opening of the optic cisterns are performed to promote brain relaxation and to identify the optic nerves, chiasm, internal carotid artery, oculomotor nerve, and tumor. Tumor removal is generally performed through a variety of surgical corridors between nerves and vessels including the prechiasmatic (subchiasmatic), opticocarotid, and carotid-oculomotor windows. A more lateral trajectory can be achieved using a pretemporal corridor. Here, the temporal bridging veins to the sphenoparietal sinus are coagulated and divided so that the temporal lobe can be mobilized posteriorly. This maneuver provides an excellent lateral trajectory exposure to the ipsilateral tentorial incisura, oculomotor nerve, carotid artery, and optic nerve.

Figure 1.

One-piece modified orbitozygomatic craniotomy. A: The patient is positioned supine with head turned to contralateral side about 30° to 45°. Curvilinear skin incision is made behind the hairline. B and C: A frontotemporal craniotomy incorporates the orbital rim and upper zygoma bone as a single bone flap. A Medpor Titan implant is used to reconstruct the pterion defect at the time of closure (B). D: Extensive removal of the sphenoid wing allows a basal trajectory to the parasellar region.

A large number of craniopharyngiomas are in the retrochiasmatic location, under the chiasm and extending up into the third ventricle. When approached from above with an orbitozygomatic approach, a retrochiasmatic tumor can often be hidden from the operative view, especially with a prefixed chiasm, and trans–lamina terminalis exposure would be necessary to access the tumor. Working in narrow corridors between the nerves and arteries can be surgically challenging with increased risk of neurovascular manipulation of critical structures. Moreover, this approach provides poor visualization of the undersurface of the chiasm where critical perforators supply the visual apparatus. There is also poor visualization of the critical plane between the tumor capsule and the hypothalamus, a location where tumor is often adherent. Dissection of this plane most often results in blind manipulation, thus increasing the risk of potential injury.

Illustrative Case 1: Orbitozygomatic Approach for Lateral Transsylvian Extension. This 69-year-old man presented with increased weakness on the left side and progressive falls along with a left homonymous hemianopsia. MRI demonstrated a large cystic lesion occupying the anterior skull base, suprasellar region, and interpeduncular fossa with lateral extension into the right sylvian fissure causing symptomatic compression on the right temporal lobe, cerebral peduncle, and optic tract (Fig. 2). Based on the extent of lateral extension into the sylvian fissure, a modified orbitozygomatic approach was chosen for transsylvian exposure and pretemporal access to visualize the tentorial incisura. EEA would not be favorable for safe exposure in this particular case because of the tumor location lateral to the carotid artery and extension into the sylvian fissure.

Figure 2.

Illustrative Case 1 imaging. A–C: Preoperative sagittal (A) and coronal (B) T1-weighted, and axial FLAIR (C) MR images demonstrating a large cystic craniopharyngioma occupying the suprasellar region and interpeduncular fossa with lateral extension into the right sylvian fissure causing symptomatic compression on the right temporal lobe, cerebral peduncle, and optic tract. There is also another component of tumor along the anterior skull base and prechiasmatic space. Near-total resection was achieved via a modified orbitozygomatic approach. D–F: Corresponding postoperative gadolinium-enhanced T1-weighted MR images showing minimal residual enhancement near the optic chiasm where there was adherent tumor residue.

After wide splitting of the sylvian fissure and posterior mobilization of the temporal lobe, we identified the large, greenish-colored, cystic craniopharyngioma situated between the temporal lobe and the internal carotid artery (Fig. 3A). There was also a solid, calcified lesion in the prechiasmatic cistern compressing both optic nerves (Fig. 3B). We then proceeded to dissect the cystic tumor from the sylvian fissure that was located lateral to the carotid artery. The cyst wall was eventually entered and greenish fluid with cholesterol crystals was expressed. Care was taken not to decompress the cyst too quickly so that enough intracystic turgor remained to provide a "surgical handle" and countertraction for continued microsurgical dissection off of critical structures. The cyst wall was peeled off of the temporal lobe on the lateral side and off of small perforating vessels on the medial side. A small microscopic remnant of the cyst wall was left due to strict adherence to perforators coming off of the posterior communicating artery and anterior choroidal artery. After decompression of the cerebral peduncle, the oculomotor nerve was visualized along with the posterior cerebral artery, superior cerebellar artery, and basilar artery (Fig. 3C and D). A near-total resection was achieved, leaving adherent tumor residue to preserve critical neurovascular structures and perforators.

Figure 3.

Illustrative Case 1 intraoperative photographs. A: Right-sided transylvian exposure of tumor (T) located lateral to the right internal carotid artery (IC) and right optic nerve (ON). B: More tumor (T) is identified in the prechiasmatic window with a small calcified piece (asterisk) adherent to the right optic nerve (ON). C and D: After near-total resection of the tumor, the oculomotor nerve (III) and P2 are visualized. The basilar artery (BA) and right superior cerebellar artery (SCA) are visualized within the carotid-oculomotor window.

Postoperatively, the patient had improved vision and transient worsening of weakness on the right side that resolved completely by the 6-week follow-up visit. Postoperative MRI showed minimal residual enhancement near the optic chiasm where there was adherent tumor residue. The patient subsequently underwent adjuvant fractionated radiation therapy without any neurological complications. This case illustrates the choice of an anterolateral transsylvian approach based upon lateral extension of the tumor.

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