Minimally Invasive Approach to Frontal Fossa and Suprasellar Meningiomas

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CHAPTER 31 Minimally Invasive Approach to Frontal Fossa and Suprasellar Meningiomas

Manoel A. de Paiva Neto, Nasrin Fatemi, Joshua R. Dusick, Dennis Malkasian, Daniel F. Kelly

INTRODUCTION

During the last two decades, as a result of advances in low-profile instrumentation, surgical navigation, and endoscopy, keyhole surgical routes have been increasingly used to approach a wide spectrum of brain and skull-base tumors. For frontal fossa and suprasellar meningiomas, the extended transsphenoidal and the supraorbital “eyebrow” craniotomies are now often used for their removal.¹^–²⁰ Although these two approaches traverse entirely different anatomic territories to reach the same intracranial target and have markedly different closure requirements, they are similar in their technically demanding nature, requiring an ability to maneuver through a narrow operative corridor. The transsphenoidal approach, which obviates brain retraction, minimizes optic apparatus manipulation, and allows early identification of the pituitary gland and infundibulum, has been shown to be effective for smaller midline meningiomas.^1,^2,^6,^7,^9,¹⁶ It is increasingly performed via an endonasal approach with microscopic and endoscopic assistance^1,^2,^7,^9,^13,^14,¹⁶ or by a purely endoscopic approach.^6,¹⁵ The two major drawbacks of the endonasal approach are (1) limited access to lesions lateral to the supraclinoid carotid arteries and optic nerves and (2) challenges in achieving an effective skull-base closure. Supraorbital keyhole craniotomy is also performed with minimal or no brain retraction and allows excellent access to a broader region within the frontal fossa and suprasellar area.^3,^4,^8,^11,^12,¹⁷^–²⁰ The minimal scalp tissue and muscle dissection required promote a less painful recovery compared to standard craniotomies.^3,¹⁷^–²⁰ The major drawback of this approach is the potential for limited maneuverability given the small craniotomy, which typically measures 15 to 20 mm by 25 to 30 mm. Herein we describe the use of the endonasal and supraorbital keyhole approaches for removing frontal fossa and suprasellar meningiomas, including a discussion of selection criteria for their use, their respective limitations, potential pitfalls, success rates, and complications.

EPIDEMIOLOGY AND INCIDENCE

Meningiomas of the anterior cranial fossa arise in various locations and comprise approximately 12% to 22% of all intracranial meningiomas.²¹^–²³ They are commonly divided into two major subgroups: olfactory groove meningiomas that arise over the cribriform plate and frontosphenoid suture and suprasellar meningiomas, the most common of which are midline tuberculum sellae meningiomas. Other suprasellar meningiomas may arise from the diaphragma sellae itself or from the arachnoidal attachments along the anterior and posterior clinoids. Some frontal fossa meningiomas span both the olfactory groove and tuberculum sellae territories and are not easily classified.^23,²⁴ Most olfactory groove meningiomas become rather large before producing symptoms (often >3 cm in size) such as headache, personality changes, anosmia, or seizures. Large olfactory groove meningiomas that extend posteriorly to the posterior planum may encroach upon the optic apparatus producing visual loss.²⁴^–²⁶ In contrast, most tuberculum sellae and other suprasellar meningiomas are diagnosed at a smaller size as a result of visual loss from chiasmal or optic nerve compression.²⁷^–³⁰ With progressive growth, tuberculum sellae meningiomas develop lateral and superior extensions, often resulting in vascular encasement, cavernous sinus invasion, and optic canal invasion. Larger tumors typically, greater than 3 or 4 cm in diameter, often encase the anterior cerebral artery complex.

HISTORY AND EVOLUTION OF MICROSURGERY FOR FRONTAL FOSSA AND SUPRASELLAR MENINGIOMAS

Traditional Approaches

Many macrosurgical and microsurgical series for removal of olfactory groove and suprasellar meningiomas have been published since the first reports of removal of an olfactory groove meningioma by Durante in 1884 and of a suprasellar meningioma by Cushing and Eisenhardt in 1938.^31,³² In most series over the last two decades, olfactory groove and suprasellar meningiomas have been approached through several routes including bifrontal, unilateral frontal, pterional, and fronto-pterional.^{22–30,33–40} In microsurgical series of olfactory groove meningiomas, high rates of total tumor removal ranging from 85% to 100% are reported with both pterional and bifrontal routes with relatively low morbidity.²⁴^–²⁶ The recurrence rate ranges from 5% to 41% over 10 years and appears to be predominantly related to subtotal removal (Simpson grade 2 or higher) in the floor of the anterior cranial fossa, and the underlying ethmoid or sphenoid sinus area.^25,^26,^33,^37,^41,⁴²

Achieving complete removal of suprasellar meningiomas is often more problematic because of tumor extensions along the optic apparatus, hypothalamic–pituitary axis, anterior circle of Willis, and cavernous sinus. In recent series, total resection of suprasellar meningiomas has ranged from 67% to 100% with rates of visual decline ranging from 0 to 20% and mortality ranging from 0 to 8.7%, respectively.^22,^23,^27–30,^34–36,^38,³⁹ Even with technically demanding approaches such as extradural clinoidectomy for optic nerve decompression, visual worsening of up to 10% has been reported.^30,³⁸

Minimally Invasive “Keyhole” Approaches

As Wilson stated more than 35 years ago “the ideal exposure is one that is large enough to do the job well, while preserving the integrity of as much normal tissue as possible.”⁴³ With the development of frameless surgical navigation, endoscopy, as well as lower profile microsurgical instruments and aspirators, this “keyhole” concept has been increasingly used for removing a wide spectrum of intracranial lesions, including meningiomas.⁴⁴ This concept is based on the observation that with a small craniotomy, the available exposure expands as the distance from the bony opening increases, so that with an optimally placed craniotomy, exposure is more than adequate (Fig. 31-1). These advances in keyhole surgery have resulted in a shift away from traditional larger anterior and anterolateral skull-base approaches such as the pterional, bifrontal, and orbitozygomatic craniotomies and the midface degloving transsphenoidal approach. Likewise, there is waning enthusiasm for the transpetrosal approach for petroclival tumors and a resurgence of the retrosigmoid craniotomy and endonasal transclival approach to reach such tumors.^36,^37,^45,⁴⁶

FIGURE 31-1 Axial plane drawing showing the respective areas of access for the supraorbital eyebrow craniotomy (purple) and the extended endonasal approach (red). Note that the most anterior aspect of the frontal fossa in the cribriform plate area is a relative “blind spot” for the supraorbital approach, but this area can be somewhat visualized with endoscopy. Also note that endonasal access is restricted to within 15–20 mm bilaterally off the midline plane and that suprasellar meningiomas that extend well lateral to the lateral border of the supraclinoid carotid arteries or lateral to the optic canals are not accessible. In addition, endonasal removal of olfactory groove meningiomas has only been described using a fully endoscopic technique.

Supraorbital approach

The supraorbital approach has evolved from more traditional frontal and frontotemporal approaches.⁴⁷^–⁵⁰ The small craniotomy with an incision directly through the eyebrow obviates problems with mastication and temporalis wasting because of limited temporal muscle dissection and retraction. More importantly, placement of the craniotomy immediately above the orbital roof and along the floor of the frontal fossa affords access with minimal brain exposure and brain retraction.^3,¹⁸ As recently demonstrated in an anatomic study by Figueiredo and colleagues using a slightly larger (30 mm) supraorbital craniotomy than is typically possible through an eyebrow incision, the area of exposure was similar between the supraorbital and traditional craniotomies, although it affords narrower angles of exposure.⁵¹ However, even with the narrower angles of horizontal and vertical exposure using the supraorbital craniotomy, many lesions of the frontal fossa and parasellar area are readily accessible as shown by Perneczky and others.^3,^4,^18,⁴⁴ Similar rates of total or near total resection of anterior cranial fossa meningiomas using the supraorbital approach have been reported when compared to traditional transcranial approaches (Table 31-1), ranging from 86% to 100% by the supraorbital route for olfactory groove meningiomas,^4,^18,¹⁹ and from 40% to 100% for suprasellar meningiomas.^4,^11,¹⁷^–¹⁹ In these series, incomplete resection was typically attributed more to tumor invasiveness as opposed to inadequate exposure.^4,^11,¹⁷^–¹⁹

TABLE 31-1 Supraorbital craniotomy for olfactory groove and suprasellar meningiomas

Extended endonasal transsphenoidal approach

The transnasal approach is also considered a keyhole approach with the exposure expanding from the piriform aperture for the sublabial transsphenoidal approach or from the nostril for the endonasal approach. The obvious advantage of these approaches for midline frontal fossa and parasellar meningiomas is that the nasal cavity and ethmoid and sphenoid sinuses provide a direct route to the tumor without the need for brain retraction. In 1987, Weiss described the microscopic extended approach for the treatment of supradiaphragmatic craniopharyngiomas.⁵² Subsequent modifications of this approach have been described by multiple groups including the endonasal endoscope-assisted method and the fully endoscopic endonasal method for removal of suprasellar and olfactory groove meningiomas.^1,^2,^5–7,^9,^10,^14–16,^53,⁵⁴ In several recent reports, the extended transsphenoidal approach for tuberculum sellae meningiomas has yielded total or near total removal rates of 57% to 85% with tumor sizes ranging from 12 to 37 mm (Table 31-2).^2,^6,^9,¹⁴^–¹⁶ Transsphenoidal removal of tuberculum sellae meningiomas appears to result in similar visual recovery rates and visual worsening rates compared to transcranial approaches, although in one recent report by Kitano and colleagues, visual recovery was better by the transsphenoidal route.^6,^14,¹⁵ Visual improvement has ranged from 33% to 100%, with most reports noting greater than 50% visual improvement while visual decline has ranged from 0 to 38%, although visual worsening is less than 20% in most reports.^2,^6,^7,¹⁵ The most common complication associated with the transsphenoidal or endonasal removal of suprasellar meningiomas has been inadequate skull-base repair and postoperative cerebrospinal fluid (CSF) leaks. In recent series of endonasal endoscopic and transsphenoidal microscopic approaches, the rates of postoperative CSF leak have ranged from 0 to 33%, although they have been decreasing in recent years.^2,^6,^9,¹⁴^–¹⁶

TABLE 31-2 Extended transsphenoidal removal of suprasellar meningiomas

Regarding endonasal removal of olfactory groove meningiomas, there is relatively limited outcome data to date. However, this is becoming a more frequently utilized route for removal of these tumors at specialized centers with considerable endoscopic expertise.^10,^53,⁵⁴ As with endonasal removal of suprasellar meningiomas, the most common complication using this approach is postoperative CSF leak.

PATIENT SELECTION FOR KEYHOLE MENINGIOMA REMOVAL

The decision to remove a suprasellar or olfactory groove meningioma through an endonasal or supraorbital route should be based on tumor anatomy, surgeon experience, and available instrumentation. Provided one has the essential instrumentation and surgical experience for either route, the major considerations are related to tumor anatomy and skull-base reconstruction.

Suprasellar Meningiomas

For tuberculum sellae and other suprasellar meningiomas, tumor size and lateral extension are the two key factors that should determine whether a transsphenoidal, supraorbital, or conventional transcranial approach is used. As our results and others suggest, most midline tuberculum sellae meningiomas less than 30 to 35 mm in diameter can be removed by either the endonasal or supraorbital routes even in the setting of a normal sized sella.^1,^2,^5–7,^9,^14,¹⁵ Both approaches allow excellent access for effective optic apparatus decompression with a high rate of visual recovery. However, the endonasal approach does not allow safe access to tumor lateral to the supraclinoid carotid arteries and the optic nerves and along much of the optic canal except medially. In contrast, the supraorbital approach allows access and excellent visualization to both of these areas. Therefore, larger meningiomas greater than 30 to 35 mm in diameter, those that extend well lateral to the supraclinoid carotid arteries or those that cause vascular encasement (see Fig. 31-1) are more safely approached by a supraorbital route or traditional transcranial approach. Regarding pituitary hormonal function, given that the pituitary stalk is pushed posteriorly by tuberculum sellae meningiomas, both the endonasal and supraorbital approaches are associated with a low rate of new endocrinopathy and a high likelihood of preserving the infundibulum. Concerning skull-base closure, a supraorbital craniotomy is relatively simple to close even if the frontal air sinus is transgressed, which occurs in fewer than 10% of cases. In contrast, endonasal avin removal of a tuberculum sellae meningioma will always result in a large skull-base defect and grade 3 CSF leak.⁵⁵ Although postoperative CSF leak rates for extended suprasellar and transplanum transsphenoidal approaches have been improving considerably during the last 5 years for both microscopic and endoscopic procedures, skull-base repair remains a major issue to consider carefully before embarking on endonasal meningioma removal.⁵⁵^–⁵⁹

Olfactory Groove Meningiomas

The ideal olfactory groove meningioma to remove by a supraorbital route is one that is less than 50 to 60 mm in maximal diameter and that does not extend to the most anterior extent of the frontal fossa, particularly on the side contralateral to the approach. Provided the tumor growth is within the arc of exposure of the supraorbital route, even meningiomas up to 100 mm in maximal diameter have been removed by this route.⁴ However, the anterior frontal fossa recess, particularly the contralateral anterior cribriform plate area, is a relative “blind spot” for the supraorbital approach.^17,⁵¹ In addition, extensive tumor invasion of the ethmoid or sphenoid sinuses may be considered a contraindication for supraorbital removal because the small craniotomy limits the ability to achieve an adequate frontal fossa floor repair should tumor removal extend into the ethmoid or sphenoid sinuses. Tumors that exhibit far anterior bilateral extension or which have extensive growth into the paranasal sinuses are probably best approached from a traditional bifrontal, pterional, or other skull-base craniotomy.^24,^26,⁴⁰

For endonasal removal of olfactory groove meningiomas, the most important consideration is tumor size, lateral extension, and whether there is vascular encasement of the anterior cerebral complex by the tumor. The small corridor between the two orbits (22 ± 4 mm)¹⁰ afforded by the extended endonasal approach allows complete resection only for tumors medial to the mid orbit as described by Kassam.(Kassam, personal communication). In addition, if there is vascular encasement of the anterior cerebral vessels by tumor, a transcranial removal is recommended. Finally, as with the extended transsphenoidal approach for tuberculum sellae meningiomas, the challenge of achieving an effective skull-base repair and avoiding a postoperative CSF leak remains a major consideration. Given these issues, endonasal removal of olfactory groove meningiomas should be attempted only by experienced endoscopic teams.^10,^53,⁵⁴

INSTRUMENTATION

Given the narrow working corridor and requirement for visualization from the operating microscope for both the supraorbital and endonasal approaches, all instruments are as low-profile as possible with angled or bayoneted handles to minimize visual obstruction and to maximize instrument maneuverability. The endonasal approach is initiated with a hand-held nasal speculum followed by insertion of a self-retaining endonasal speculum once the sphenoid keel has been exposed. Thus, Cottle dissectors, microdissectors, ring curettes, and microblades are on bayoneted handles. Similarly, microscissors, tumor grasping forceps (both straight and up-angled) are used in a single-shaft pistol-grip construct to minimize visual obstruction through these relatively narrow openings. High-speed drills and ultrasonic aspirators also are of the lowest possible diameter with angled hand pieces. Surgical navigation is also recommended for all cases for skull-base landmark identification.

Given the restricted visualization and reduced angles of exposure of any keyhole approach with an operating microscope, endoscopic visualization should be utilized in all cases, at least intermittently to provide a more panoramic view and to assist with tumor removal in the far recesses of the exposure. Endoscopes for keyhole surgery should include 4-mm rigid endoscopes (18 cm in length) with 0-, 30-, and 45-degree angled lenses (Karl Storz, Tuttlingen, Germany)⁶⁰^–⁶⁴

Use of a micro-Doppler probe for vessel localization localizing is also recommended for all keyhole approaches. For example, in the supraorbital approach, after initial tumor debulking of an olfactory groove or tuberculum sellae meningiomas, localizing the anterior cerebral artery complex behind a rind of tumor with the Doppler can be very helpful. Similarly, as we have shown previously, localizing the cavernous carotid arteries before dural opening in the endonasal approach is also highly recommended and appears to reduce the risk of a cavernous carotid injury.⁶⁵

SUPRAORBITAL “EYEBROW” CRANIOTOMY

Positioning

As previously described,^3,¹⁸ patients are placed supine in the 3-point Mayfield head holder (Ohio Medical Instrument Co., Cincinnati, OH) and angled 20 to 60 degrees to the contralateral side based on the location and projection of tumor to the right or left. For suprasellar meningiomas, 30 degrees of head rotation is used: for olfactory groove meningiomas, 45 to 60 degrees contralateral rotation is recommended. The head is slightly retroflexed and the malar eminence is most prominent point. The lower abdomen is also prepped for a possible abdominal fat graft. The patient is registered to their preoperative surgical navigation magnetic resonance imaging (MRI) and the projection of the ipsilateral frontal sinus is then marked on the supraorbital skin surface to help define the medial limits of the craniotomy. The supraorbital notch should be palpated and noted.

Initial Approach

The skin incision within the eyebrow extends from just medial to the supraorbital notch and continues laterally and inferiorly beyond the eyebrow in a skin fold along the frontozygomatic process. At its most medial aspect, the skin incision remains superficial to avoid injury to the supraorbital nerve. The skin flap is elevated superiorly to gain supraorbital exposure and retracted with multiple fish hooks. A pericranial flap is then created and incised in a half moon-shaped fashion, then retracted inferiorly along the supraorbital rim area. This pericranial flap incorporates a small portion of the most superior aspect of the temporalis fascia extending just below the superior temporal line. Additional fish hooks are then used to retract inferiorly and laterally the temporalis muscle and fascia along the inferior margin of exposure to expose the keyhole below and posterior to the frontozygomatic process (Fig. 31-2).

FIGURE 31-2 Right supraorbital craniotomy: Intraoperative photographs. A, Bone flap created but still in position. B, After bone flap removal. The pericranium and superior temporalis fascia and muscle are reflected with multiple fish hooks to allow maximal exposure. C, Intraoperative microscopic view before tumor resection. D, Intraoperative microscopic view after optic nerve decompression.

A single burr hole is placed below the superior temporal line and posterior to the keyhole with the high-speed drill. A free supraorbital half-moon–shaped bone flap is made which does not include the orbital rim and measures approximately 15 to 20 mm by 20 to 25 mm.^3,¹⁸ It is essential to drill the anterior inferior, medial inferior, and lateral inferior bone edges of the calvarium to provide the maximal angles of exposure into the frontal fossa. In addition, if there are bony protuberances along the floor of the frontal fossa in the trajectory to the parasellar area, these should be drilled as well. If the frontal sinus has been entered (which infrequently occurs), it can be sealed with bone wax at the initial opening and then more definitively repaired at the end of the procedure.

Dural Opening and Initial Exposure

The dura is opened in C-shape fashion with its base toward the orbital rim. The operating microscope is brought into use at this point. The ipsilateral olfactory tract should be identified and followed back to the ipsilateral optic nerve and carotid cistern. In some cases of olfactory groove meningiomas, however, the olfactory tract will be engulfed or elevated by tumor. The arachnoid over the opticocarotid cistern is opened sharply with egress of CSF, allowing further brain relaxation. A self-retaining brain retractor can be placed over the frontal lobe, although in most cases such retraction is needed only at the beginning of the intradural portion of the case.

Olfactory Groove Meningiomas

In approaching these frontal fossa meningiomas, the tumor edge is encountered medially and relatively anteriorly. They are mainly feed by the anterior and posterior ethmoidal arteries from below and the anterior falcine arteries from above. An initial attack on the base of the tumor along the olfactory groove provides early and effective devascularization. If possible, the ipsilateral olfactory tract should be spared and its arachnoid attachments to the tumor cut sharply. Next, central debulking of the tumor follows, typically with the ultrasonic aspirator, intermittent bipolar coagulation, and tumor grasping forceps. This debulking should also extend across the midline to the contralateral tumor. The contralateral olfactory tract should be identified at this point as well; typically its most anterior extension at the cribriform plate is the best location to identify the tract and to begin separating it from tumor. In many instances, the falx will need to be cauterized and partially resected to better visualize tumor behind the falx and to achieve complete contralateral tumor removal.

After this initial debulking, one can begin to mobilize the tumor pseudocapsule and develop the tumor–brain interface. Copious direct irrigation is used to help develop this plane and to preserve the pia-arachnoid. Cottonoids can be placed in the interface to further protect the pia-arachnoid. For larger tumors with posterior extension, it is important to localize the anterior cerebral complex and ipsilateral carotid bifurcation. The micro-Doppler probe can be very helpful for this localization by insonation directly through the tumor rind itself. The last portion of tumor typically remaining is the most cephalad and posterior rim that elevates and may partially encase the branches of the anterior cerebral artery complex. The Doppler probe and endoscopic visualization is helpful during this dissection to identify these vessels. Arteries that are only partially encased by tumor can often be sharply dissected free of tumor; however, in instances of dense tumor adhesions or complete vascular encasement, it is best to leave such remnants behind rather than risk a serious vascular injury. Similarly, if there is frank brain invasion of tumor one must decide based on the patient’s age, and overall surgical goals, whether it is reasonable to attempt a total tumor removal. After the tumor removal is as complete as possible, endoscopic visualize of the resection cavity is recommended, particularly to view the contralateral frontal fossa searching for accessible tumor remnants.

Suprasellar Meningiomas

True tuberculum sellae meningiomas will typically first be encountered on the proximal planum sphenoidale. Under microscopic visualization, the ipsilateral olfactory tract is identified and followed back to the ipsilateral optic nerve and carotid cistern. In some instances, the tumor will extend out over the proximal optic canals and obscure the optic nerves unilaterally or bilaterally. Surgical navigation can be used to precisely localize the optic canals in such cases of large tumors that obscure the origins of the optic canals. The arachnoid overlying tumor along the posterior planum and ipsilateral optic nerve and carotid cistern is opened sharply to allow atraumatic mobilization of the frontal lobes. After identification of the ipsilateral optic nerve and ICA, the tumor base is elevated off the planum with microdissectors and devascularized with bipolar cautery, taking care to avoid cautery near the optic canals. The tumor pseudocapsule is then opened and the tumor is internally debulked with the ultrasonic aspirator, microscissors, and tumor grasping forceps, taking great care not to transgress the pseudocapsule posteriorly or laterally. After the reduction of tumor volume, one should attempt to identify the medial aspect of the contralateral optic nerve and the chiasm. At this point, the micro-Doppler probe is helpful to localize the course of the anterior cerebral artery complex behind the remaining rind of tumor. Endoscopic visualization with the 0- and 30-degree endoscopes is also helpful at this point of the procedure as well. If the vessels are still quite distant by Doppler localization, then additional thinning of the pseudocapsule should be performed.

Once the posterior tumor rind is relatively thin, using sharp dissection, gentle traction, and copious irrigation, the tumor pseudocapsule is dissected away from the ipsilateral and contralateral optic nerves, optic chiasm, supraclinoid carotid arteries, and anterior cerebral complex. Great care is taken to preserve the arachnoid plane and perforators over these key structures. The infundibulum will also begin to come into view at this point. In some instances, tumor extends into a deepened sella onto the diaphragma sella and this tumor can typically be elevated away from the diaphragma and infundibulum. In cases of firm or calcified tumor remnants that are densely adherent to the optic apparatus or anterior cerebral complex, it is best to leave such tumor behind rather than risk a serious neurovascular injury. The endoscope should be brought into use again at this point to confirm as complete a tumor removal as possible. Inspection of the optic canals should also be performed to assess for intracanalicular tumor extension. Such tumor can often be removed with drilling of the roof of the optic canal and opening the dural ring over the optic nerve. Such drilling should be performed with a 2- or 3-mm diamond bit using copious irrigation. In patients with significant preoperative visual loss, some authors advocate early optic canal opening and decompression before tumor removal to minimize chances of visual deterioration associated with optic apparatus traction.^30,³⁸

Closure

After tumor removal, the dura is closed in watertight fashion with multiple interrupted 4-0 stitches. A layer of collagen sponge (Helistat or Duragen) is placed over the dura for reinforcement of the dural closure. The anterior medial aspect of the craniotomy should be checked again for a defect into the frontal sinus, which in the great majority of cases is not present. If there is no sinus defect, the bone flap is then reapproximated with a burr hole cover placed over the lateral burr hole site and contoured to the bone anatomy; a single straight titanium plate extends from the medial bone flap edge going toward the midline and is placed under the supra-orbital nerve. The burr hole site is then covered with the superior temporalis muscle and fascia. The superior and inferior edges of the bone should be placed with minimum distance from the adjacent bone and the bone gaps further filled with collagen sponge. Some advocate for optimal cosmesis, placing the bone flap so the bone gap is placed inferiorly directly under the eyebrow incision leaving no gap superiorly in the more visible forehead area.¹⁸ The pericranial flap is then returned to its anatomic position covering the bone flap and secured to the adjacent pericranium with absorbable stitches. The scalp incision is closed with galeal and subcutaneous stitches followed by topical skin adhesive such as Dermabond (Ethicon Inc., Johnson & Johnson Co., Piscataway, NJ).

The closure is slightly modified if there is a frontal sinus defect. If the entry into the sinus is small, it can be occluded with bone wax and covered with the previously elevated and vascularized pericranial flap. This can be further reinforced with a layer of collagen sponge that is layered over the exposed dura with excess collagen extending up along the frontal sinus defect. It is further reinforced by placing the anterior medial edge of the bone flap directly against the covered frontal sinus defect. Rarely, if a large frontal sinus defect has been created, it can be reinforced with an abdominal fat graft that is placed within the frontal sinus defect.

Results

Supraorbital eyebrow craniotomy has been used in 12 patients (mean age 52 ± 9 years, 83% female), including 4 with olfactory groove meningiomas and 8 with suprasellar meningiomas. Three patients with olfactory groove meningiomas with tumor diameters ranging from 18 to 50 mm had complete tumor removal without complication; another patient with prior subtotal removal and radiosurgery had a near total tumor removal given dense adhesions of the tumor to the A-2 arterial branches (Fig. 31-3). Of the eight patients with a suprasellar meningioma, five underwent first-time surgery (Fig. 31-4). Of these five, gross total, near-total (>90% resection) and subtotal removal was accomplished in two, two, and one patient respectively. All three patients with near-total or subtotal removal had cavernous sinus invasion. One patient with near-total resection was submitted to further stereotactic radiotherapy after tumor recurrence 6 months postsurgery. In three patients with recurrent tumors and gross invasion of central skull base, the surgical goal was optic pathway decompression as part a staged treatment including further transsphenoidal tumor removal in two patients. Overall, of seven patients with preoperative visual loss, improvement was observed in four (57%) patients. One patient with a 25-mm fibrous and invasive tuberculum sella and right paraclinoid meningioma who underwent subtotal removal, experienced a delayed right inferior hemianopsia that has persisted. There was one presumed cavernous carotid artery puncture injury in a patient who had undergone two previous surgeries. Arterial bleeding was controlled with muslin gauze; a postoperative cerebral angiogram was entirely normal and the patient had no new neurologic deficits.

FIGURE 31-3 Supraorbital removal of an olfactory groove meningioma. A 69-year-old woman was found to have a 50 × 35 × 37 mm homogeneously enhancing frontal fossa meningioma without extension into the paranasal sinuses. She underwent complete tumor removal and her 6 month postoperative MRI shows no evidence of residual or recurrent tumor.

FIGURE 31-4 Supraorbital removal of a tuberculum sellae meningioma. A 43-year-old pregnant woman with a 3-month history of visual decline was found to have a 30 × 31 × 26 mm meningioma depressing the pituitary gland and displacing the infundibulum posteriorly. She underwent complete tumor removal and had successful delivery of her twins 3 months after surgery. Her vision improved and her 6-month postoperative scan shows a complete tumor removal; she had an excellent cosmetic result.

EXTENDED ENDONASAL APPROACH

Positioning

After induction of general anesthesia, patients are placed in the supine, semi-slouch position, with the head resting freely in the horseshoe head-holder angled approximately 30 degrees toward the left shoulder. The three-point head holder is attached to the patient’s head but not to the table. The surgical navigation (BrainLab VectorVision Cranial, Westchester, IL) localizing device is applied and the patient is registered to their preoperative MRI. The head is slightly extended more so than for a sellar lesion so that the surgeon has an angle of approach to the tumor of approximately 45 degrees to the horizontal plane. The nostrils are swabbed briefly with butadiene and the right lower abdomen is prepped for a possible fat graft. Perioperative antibiotics (cefazolin) are given for 24 hours.

Nasal Portion and Sphenoidotomy

As previously described, the direct endonasal approach is performed with the operating microscope and endoscopic assistance.^1,^7,⁶⁶ For tumors projecting more to one side, the contralateral nostril is chosen to provide better tumor access. The initial approach is performed with the operating microscope. A hand-held speculum is passed into the nostril along the trajectory of the middle turbinate. A vertical mucosal incision is made at the junction of the sphenoid keel and posterior nasal septum with a bayoneted Cottle elevator by sweeping the mucosa laterally. The posterior nasal septum is then pushed across the midline with the tip of the hand-held speculum and a similar mucosal flap is elevated on the contralateral side of the sphenoid keel. This exposure should allow identification of both sphenoid ostia which should be seen at approximately the 9 to 10 o’clock and 2 to 3 o’clock positions.

Next, a short endonasal (60 or 70 mm) speculum (Mizuho America, Inc., Beverly, MA) is passed inside the hand-held speculum and the hand-held speculum is disengaged and removed in two separate halves. In most recent suprasellar endonasal cases, we use a 60-mm trapezoidal-shaped endonasal speculum (Mizuho America) that provides expanded superior visualization with the microscope and allows greater maneuverability of the endoscope and other instruments.⁶⁷ To gain full visual advantage of the short speculum, and to maximize superior visualization, the most superior aspect of the sphenoid keel and soft tissue at the posterior ethmoid roof area should be removed. In addition, it is helpful to remove at least 10 to 15 mm of posterior nasal septum and lateral tissue as well so that no soft tissue or bone obstructs visualization medial to the distal speculum blades.

Sellar and Planum Exposure

After the wide sphenoidotomy is performed, the sellar face is removed followed by removal of the tuberculum sella and proximal planum sphenoidale. This bony removal is performed with a Kerrison rongeur and a high-speed diamond bit drill (Anspach, Palm Beach Gardens, FL) and is tailored to the patient’s specific tumor anatomy. Surgical navigation is very helpful to gauge the extent of bony removal needed at the level of the posterior planum. In addition, the width-limiting structures at the level of the tuberculum sella are the optic canals. Care must be taken in the bony removal in this region. In addition, the micro-Doppler probe is always used for carotid localization before dural opening. Inferiorly, a lip of sellar bone should remain that is very helpful for the skull base reconstruction phase of the procedure.

Dural Opening and Tumor Removal

A Y-shaped dural opening is typically performed that begins in the midline and extends both above and below the level of the diaphragma sella. The dura is further opened inferiorly as needed to better visualize the inferior–lateral recesses of the suprasellar space and the superior surface of the pituitary gland and infundibular insertion. After the initial midline suprasellar dural opening has been extended laterally, further dural cauterization is typically needed to reduce tumor blood supply. These typically fibrous and rubbery tumors are then debulked internally with microscissors and cauterization. Tumor debulking continues centrally using straight and curved microscissors and bipolar cautery. After this initial debulking, gentle traction with Decker forceps is used to carefully pull the more lateral and anterior aspects of the tumor into view, taking great care to preserve the arachnoid plane over the optic chiasm and optic nerves. The diaphragma sellae inferiorly also is left intact, unless tumor is arising from it. As the tumor is reduced further, the pituitary stalk and its insertion into the pituitary gland through the diaphragma sellae are visualized and carefully dissected away from the tumor pseudocapsule. Intermittent use of the 0-, 30-, or 45-degree angled endoscopes is helpful to visualize residual tumor and its relationship to key structures such as the anterior cerebral artery complex. Further arachnoid attachments to the tumor laterally and superiorly along the optic nerves and optic chiasm are cut sharply with microscissors. Ultimately, the remaining tumor, with its pseudocapsule largely intact, then is removed in several relatively large pieces after further reducing tumor bulk with the bipolar cautery instrument. After tumor removal appears complete, a final look with the 30- and 45-degree endoscopes is performed to assess for residual tumor. Tumor within the cavernous sinus is generally not resected.

Skull-Base Reconstruction and Nasal Closure

After removal of a tuberculum sella meningioma, a large (grade 3) CSF leak results which is closed in a multilayered fashion.⁵⁵ As described previously, first an abdominal fat graft is placed in the intrasellar/suprasellar dead space followed by a layer of collagen sponge placed over the fat. A piece of precisely cut titanium mesh is placed over the collagen sponge. The mesh is shaped to conform precisely to the defect and includes a small handle so that it could be maneuvered into the intrasellar extradural space in cephalad-to-caudal direction. Care is taken to trim sharp edges off the mesh and ensure that there is no encroachment on the optic canals or cavernous sinus. An additional concern in grade 3 leaks is the possibility of intra dural graft migration because there is typically a large diaphragmatic and/or dural defect through which the fat graft and collagen may migrate. Thus, in assembling the graft it is important to have portions of the fat and collagen extending out extradurally on at least two sides of the defect so that when the mesh is placed in the extradural bony defect, it holds the fat and collagen against the edges of the bony and dural defect, thereby preventing intradural graft migration. At this point, the anesthesiologist should induce a Valsalva maneuver to stress the repair. If there is seen to be copious CSF streaming around the repair or the titanium mesh becomes dislodged, it should be appropriately revised. Once the Valsalva maneuver confirms an adequate and stable repair, additional fat is placed in the sphenoid sinus against the titanium mesh and covered by a thin layer of BioGlue to hold the construct in position.⁶⁸ The endonasal speculum is removed, nasal hemostasis is obtained with Surgifoam, the ipsilateral middle turbinate which is out-fractured at the beginning of the procedure, is medialized and the nasal septum is returned to the midline. No nasal packing is placed. Before awakening the patient from anesthesia, a lumbar drain is placed for CSF diversion at 5 to 10 mL/h for the first 48 hours after surgery. As described previously, however, the lumbar drain is not opened until an early postoperative CT scan is performed to document the amount of immediate postoperative pneumocephalus and to insure that the repair materials are in good position.⁵⁵