ORIGINAL ARTICLE
Update on endoscopic endonasal resection of skull base meningiomas Joseph Brunworth, MD1 , Vikram Padhye, MBBS2 , Ahmed Bassiouni, MBBCh2 , Alkis Psaltis, MBBS, PhD, FRACS2 , Stephen Floreani, MBBS, FRACS2 , Simon Robinson, MBChB, FRACS3 , Stephen Santoreneos, MBBS, FRACS4 , Nick Vrodos, MBBS, FRACS4 , Andrew Parker, MBBS, FRACS5 , Agadha Wickremesekera, MBChB, FRACS, MD5 and Peter-John Wormald, MBChB, FCS, FRCS, FRACS2
Background: The objective of this work was to report success rates as well as potential obstacles in transnasal endoscopic resection of anterior skull base meningiomas. Methods: The study design was a case series with chart review at tertiary referral centers in South Australia and New Zealand. The patients were 37 consecutive patients who underwent endoscopic resection of skull-base meningiomas between 2004 and 2013. Review of patient charts and operative details were performed. Outcomes including complications are reported. Results: Eighty-four percent of patients were women. There were 28 primary and 9 revision cases. Tumor locations were as follows: 14 olfactory groove/subfrontal; 12 planum/jugum sphenoidale; 7 tuberculum sellae; 3 clinoidal; and 1 clival. Vision change was the most common presenting symptom. Mean tumor volume was 33.68 cm3 , mean diameter was 2.78 cm. Average operating times decreased with an initial learning curve and then plateaued. Primary tumors larger than 60 cm3 took an average of 10 hours to resect. Gross total removal was achieved in 29 patients. There were no perioperative deaths. Two deaths occurred within 1 year of surgery. Postoperative cerebrospinal fluid (CSF) leaks occurred in 13 patients. Seventy-five percent of patients presenting with visual loss reported visual
1 Department
of Otolaryngology, St. Louis University Hospital, St. Louis, MO; 2 Department of Otolaryngology, Queen Elizabeth Hospital, Woodville South, SA, Australia; 3 Department of Otolaryngology, Wellington Hospital, Wellington, New Zealand; 4 Department of Neurosurgery, Royal Adelaide Hospital, Adelaide, SA, Australia; 5 Department of Neurosurgery, Wellington Hospital, Wellington, New Zealand Correspondence to: Joseph Brunworth, MD, St. Louis University Hospital, Dept of Otolaryngology, 6th Floor, Desloge Towers, 3635 Vista Ave, St. Louis, MO 63110; e-mail: [email protected] Potential conflict of interest: Although not directly related to this study, Peter J. Wormald receives royalties from Medtronic ENT and is a consultant for NeilMed. The remaining authors have no conflicts of interest. Received: 28 August 2014; Revised: 16 October 2014; Accepted: 30 October 2014 DOI: 10.1002/alr.21457 View this article online at wileyonlinelibrary.com.
improvement. Of the 29 patients considered to have had complete resection at surgery, one was found to have residual disease on a postoperative magnetic resonance imaging (MRI) and another one later developed radiological evidence of recurrence. Conclusion: Using a 2-team approach, meningiomas of the skull base were successfully removed via an intranasal endoscopic technique. Although complete resection is typically possible even with large tumors, the lengthy resection required time for tumors larger than 60 cm3 (diameter ࣙ4 cm) may obviate some of the advantages of this approach. The rate of postoperative CSF leak decreases when a synthetic dural substitute is added but does not apC 2014 ARS-AAOA, LLC. proach zero.
Key Words: intranasal; endoscopic; anterior; skull base; meningioma; endonasal resection; olfactory groove; anterior cranial fossa; subfrontal How to Cite this Article: Brunworth J, Padhye V, Bassiouni A, et al. Update on endoscopic endonasal resection of skull base meningiomas. Int Forum Allergy Rhinol. 2015;5:344–352.
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he intimate relationship between anterior skull-base meningiomas and the surrounding neurovascular structures of the brain makes their removal a surgical challenge. With the exception of infrequent cases that have more aggressive histologic features, the majority of these tumors exhibit a slow growth pattern and have a low chance of recurrence if complete resection is achieved.1–4 The challenges encountered during surgery coupled with the potential for highly successful outcomes makes this an exciting frontier for surgeons and for the further development of the field.1, 5 The traditional approach to these tumors entails a craniotomy and often requires a degree of frontal lobe retraction for access.6 Even with utmost care, such retraction has been implicated in changes to the disposition of postoperative patients.6–9 Other disadvantages of this invasive approach include bone flap complications
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and cosmetic deformities.10, 11 With advances in endoscopic surgical instrumentation and techniques, the intranasal endoscopic removal of meningiomas poses an attractive alternative, circumventing the need for an external incision and frontal lobe retraction. In addition, as many of these tumors have an intimate relationship to the skull base, this more direct inferior approach afforded endonasally may reduce the need to cross neurovascular structures.1, 12–17 Although endoscopic techniques offer potential advantages, such surgery is not without its challenges and complications. As more institutions convert from traditional open craniotomy techniques to the minimally-invasive intranasal endoscopic route, reporting success rates as well as identifying potential complications becomes essential. This review reports our institution’s experience with the endoscopic resection of meningiomas.
Patients and methods Data collection A retrospective chart review was performed on all consecutive patients undergoing purely endoscopic intranasal approaches to anterior skull-base meningiomas from 2004 to 2013 at the South Australia Endoscopic Skull Base Unit (SAES) and Wellington Skull Base Units. A total of 37 patients with anterior skull-base meningiomas were resected using a wholly intranasal endoscopic approach and were included in the study. The Central Northern Adelaide Health Service Ethics of Human Research Committee granted approval of this study. Demographic, clinical, and tumor information was obtained via review of patients’ charts, magnetic resonance imaging (MRI), histology reports, operative notes, and intraoperative videos recorded for all cases. Tumor dimensions including area (cm2 ) and volume (cm3 ) were obtained via MRI measurements in all planes. The extent of resection was determined from operative notes and correlated with the intraoperative videos and postoperative histopathology reports. Complications were noted in the patients’ charts and are comprehensively detailed below. Patients who underwent tumor debulking when complete resection was not considered feasible are reported as residual rather than recurrent tumors and are specified as such.
Surgical method Preparation All patients were discussed preoperatively at our bimonthly skull-base meeting to ensure all surgeons were in agreement with the plan of care. Patients were prepped using a sterile technique including half-strength Betadine for facial prep and separate sterile fields for abdominal or thigh graft harvesting sites. Image guidance (StealthStation Medtronic Surgical Technologies, Jacksonville, FL) was used during all cases, merging the patient’s preoperative computed tomog-
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raphy (CT) with their MRI so that both imaging modalities could be used intraoperatively. Preoperative injection was performed with local anesthetic (2 mL of 2% lignocaine with 1:80,000 adrenaline) followed by placement of vasoconstrictive neuropatties (2 mL of 10% cocaine, 2 mL of 1:1000 adrenaline, and 2 mL of 9% saline). Reverse Trendelenburg and elevation of the head of bed was combined to a total of approximately 30 degrees. An indwelling catheter, large bore intravenous (IV) access, arterial line, and appropriate anesthetic monitors were placed before commencing surgery. Prophylactic antibiotics and deep venous thrombosis (DVT) compression stockings and sequential suppression devices were placed. In no cases was a prophylactic lumbar drain placed.
Surgical approach Surgeries were performed using a 2-team binostril endonasal technique. In all cases, the otolaryngology team performed the initial surgical approach. Septoplasty was performed if deemed necessary for access. A pedicled nasoseptal flap as first described by Hadad-Bassagasteguy was then raised and stored in the ipsilateral nasopharynx or maxillary sinus for later use in the reconstruction of the skull-base defect.18 The longest and broadest possible flap was harvested to ensure adequate extension over the skullbase defect. This flap was obtained early in the procedure to ensure that the posterior septal artery was carefully preserved within the flap and not injured during subsequent sphenoidotomy work. In rare cases of large defects, bilateral Hadad flaps were harvested and stored. In cases where only one flap was raised, a contralateral reverse rotation flap was used to cover the exposed septal cartilage at the donor site (Fig. 1). The subsequent degree of sinus surgery performed largely depended on the location of the tumor. In general, bilateral middle meatal antrostomies, total sphenoethmoidectomies, and frontal sinusotomies were performed in all cases to augment surgical access, allow identification of vital structures (skull base, orbit, orbital apex, carotid artery, and optic nerve), and reduce the risk of iatrogenic sinusitis. Additional procedures were performed according to tumor location. Patients with subfrontal tumors or tumors with extension anterior to the anterior ethmoidal artery had an endoscopic modified Lothrop/Draf 3 procedure performed (Fig. 2). All clival, clinoidal, tuberculum sellae, and planum/jugum sphenoidale patients had wide sphenoidotomies and excision of the superior turbinates for access. Upon clearance of all skull-base partitions, vascular control was gained of the anterior and posterior ethmoid arteries. Identification and ligation of these vessels was achieved at the midpoint of the ethmoidal roof rather than at their lateral entrance to minimize the risk of vessel retraction into the orbit and subsequent orbital hematoma.12 At this point, circumferential bony osteotomies were performed with the skull-base drill (3 mm skull base or Stylus coarse diamond bur; Medtronic Surgical Technologies, Jacksonville, FL) to
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FIGURE 1. Reverse septal flap. (A) Dotted line represents intended pedicled septal flap with posterior septal branch of the sphenopalatine artery providing the blood supply. (B) Pedicled Hadad flap tucked into ipsilateral choana. Dotted line represents intended cut to be made on the medial surface of the contralateral septal mucosa. (C) The contralateral septal mucosa is then brought forward to cover the remaining anterior septum and is sutured into place using a standard quilting stitch. R (Integra Lifesciences, trasonic Surgical Aspirator (CUSA) York, PA) can be used, depending on surgeon preference. In this manner, complete tumor resection with preservation of surrounding vasculature can typically be achieved with clearance confirmed through the use of angled endoscopes.
Skull base reconstruction
FIGURE 2. Coronal MRI at the level of the anterior ethmoidal artery showing tumor extends further anteriorly. This patient’s approach would include a frontal drillout (endoscopic modified Lothrop/Draf 3 procedure) to ensure adequate access anteriorly. MRI = magnetic resonance imaging.
expose the underlying dura without penetration. At this point in the dissection, the 2-surgeon technique was used. The endoscope was held by the otolaryngologist allowing the neurosurgeon to use both hands for the tumor resection. We have found that more room can be provided for surgical instrumentation by positioning the endoscope in a superolateral position (on the patient’s right side) and maintaining an off-centered endoscopic view. Although a 0-degree endoscope is used for the majority of the procedure, angled scopes can also be used at various times if further visualization is needed during the dissection. Bipolar cautery is typically applied to the dura prior to its incision to seal any dural venous vessels. Once the dura is incised, the tumor is debulked from inside out, collapsing the tumor and allowing the tumor edges to be brought into the involuted central area. This is generally considered a safer zone of dissection and allows excellent visualization of the arachnoid plane that can then be carefully teased from the tumor. Within this safer zone of dissection, additional R ultrasonic aspisurgical instruments such as the Sonopet rator (Stryker Corp., Kalamazoo, MI) or the Cavitron Ul-
After tumor removal, attention is turned toward repair of the skull-base defect. This is performed in a multilayered fashion, can be varied in technique19 , and is done in a manner most appropriate for the defect at hand. Most commonly, an underlay graft is placed within the cranial vault. This can be of autologous origin such as tensor fasR (Intecia lata or a synthetic material such as Duragen gra Life Sciences Holdings Corporation, Plainsboro, NJ), which we most commonly used in our series. Our experience with larger skull base defects and the possibility of a degree of frontal lobe collapse has resulted in us now reinforcing the skull-base repair with a rigid support in the form of autologous septal cartilage or a mesh titanium plate (Medtronic Surgical Technologies, Jacksonville, FL). For these larger defects, we also add a second overlay support R . The in the form of fascia lata or second layer of Duragen vascularized septal flap is then rotated into place, ensuring that the mucosal surface is facing intranasally. Caution is taken to circumferentially sit the flap directly onto bone to facilitate graft adherence. Following this, small pieces of R mesh (Ethicon, Somersville, NJ) are placed cirSurgicel cumferentially around the edges of the flap to seat the graft directly against the bone and prevent the edges from lifting when a tissue sealant such as DuraSealTM (Confluent R Surgical, Waltham, MA) is then applied. After Surgicel TM and DuraSeal have been applied, intranasal counter supR (Pfizer, New York City, port is achieved with Gelfoam NY) followed by bismuth iodoform paraffin paste (BIPP)soaked ribbon gauze (BIPP; Orion Labaratories, Balcatta, Australia). This gauze is kept in place for 7 days and removed in the clinic setting.
Follow-up Patients were extubated postoperatively and kept overnight in the intensive care unit for close neurological monitoring.
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Most patients had a CT scan on postoperative day 1 to confirm the reconstruction remained in correct position and that no significant intracranial air or bleeding had accumulated. After patients were cleared for discharge, follow-up was arranged with both the neurosurgical as well as otolaryngology teams. Nasal saline rinses were commenced upon removal of the BIPP-soaked ribbon gauze. Patients without unusual circumstances had a postoperative MRI at 3 months and yearly thereafter.
Results Demographic and clinical information Thirty-seven patients with anterior skull-base meningiomas undergoing solely intranasal endoscopic resection between 2004 and 2013 were identified and included in the study. Eighty-four percent (n = 31) were female, with an average age of 53 years. Visual change was the most common presenting symptom, described by 60% of patients (22/37). Most commonly the visual change correlated with optic chiasm or tract compression. The second most common presenting symptom was headache (16%; 6/37). Other presenting symptoms included epistaxis, seizures, fatigue, anosmia, or a combination of the previously mentioned symptoms.
Tumor characteristics Tumor location included the following: 14 olfactory groove/subfrontal, 12 planum/jugum sphenoidale, 7 tuberculum sellae, 3 clinoidal, and 1 clival. Tumor size varied from 1.26 (1.5 × 1.2 × 0.7) cm3 in volume up to the largest measuring 130.5 (5.8 × 5.0 × 4.5) cm3 . The mean volume of the tumors was 33.7 cm3 , with a mean size area of 9.9 cm2 (range, 1.6 to 29 cm2 ), and mean diameter of 2.78 cm (range, 0.7 to 5.8 cm).
Surgical statistics Twenty-eight were primary cases and 9 were revisions. Of the revision cases, 7 initially had open approaches and the remaining two had prior endonasal approaches.
Operative times Operative time ranged from 2 hours 55 minutes to 12 hours 43 minutes. This was influenced by surgical experience, size of the tumor, preservation of an arachnoid plane at the brain/tumor interface, and the proximity and encasement of critical neurovascular structures. Operative times generally decreased with increasing surgical experience. The first 7 cases averaged 8 hours 15 minutes decreasing to an average of 5 hours 41 minutes thereafter. Large tumors, greater than 4 cm in diameter or more than 60 cm3 in volume, typically required over 10 hours to resect irrespective of surgical experience (Fig. 3). In only one instance was a primary tumor with a mean volume greater than 50 cm3 able to be resected in less than 7 hours. Preservation of the tumor/arachnoid plane also influenced resection time. If the arachnoid plane
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was preserved, the resection was rapid. In contrast, loss of this plane required meticulous dissection of each blood vessel off of the tumor, thereby increasing surgical time. An indication as to whether or not the arachnoid plane was likely to be preserved was the amount of brain edema seen at the interface between the tumor and the brain on the MRI scan. As a validated grading system for edema associated with tumors does not currently exist, we did not attempt to grade the extent of edema, but rather noted its presence or absence. Brain edema was noted in 7 of our cases. An additional time factor was encasement of the anterior cerebral arteries (found in 8 patients). In a number of cases there was encasement of the A1, ACom, and/or A2 sections of the anterior cerebral arteries. In these cases, careful dissection and preservation of the vessels added significantly to the operative time.
Extent of resection Gross total resection was achieved in 29 of the 37 patients (78.4%). Subtotal resection and tumor debulking were performed in 8 patients for whom total resection was not achievable without a high risk of significant morbidity and possible mortality. One-half of these were revision cases extending deep into the cranial vault or clinoid region with symptoms from mass effect in which debulking was required for deteriorating neurology. The others were scheduled for excision and found intraoperatively to be unsafe for complete resection due to tumor encased neurological structures or major blood vessels. A Fisher’s exact test showed a statistically significant increase in the chance for residual or recurrent disease when the tumor was shown to encase major blood vessels on preoperative imaging (p = 0.007). Of the revision cases, no distinguishing factors were identified in those patients with prior open procedures vs those with prior endoscopic procedures. In both groups, as in most revision cases, the planes tended to be more obscured and a slower, more meticulous dissection technique was warranted. Having a recurrence also increased the patient’s chance of incomplete resection on the second attempt as many of these cases were for tumor debulking and attempts at symptomatic improvement. All patients with incomplete resection were re-presented at tumor board for additional treatment options including observation, planned re-operation, radiotherapy, or other treatment modalities. Of the 9 revision cases in the series, 3 had already undergone radiotherapy prior to their revision surgery.
Complications In this series, the most common complication was postoperative cerebrospinal fluid (CSF) leak, requiring return to the operating theatre in 4 of 37 patients (11%). An additional 9 (24%) responded to lumbar drain alone. Of the CSF leaks recorded, 3 out of the first 4 procedures were affected, suggesting a steep learning curve for skull-base
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FIGURE 3. Graph depicting the initial learning curve (the first 7 cases averaging 8 hours 15 minutes), subsequent improved operating times (remaining cases averaging 5 hours 41 minutes). Cases marked with an asterisk (*) had an average diameter of 4.5 cm and average operating time of 12 hours 5 minute. These three were also identified to have edema and encasement of vasculature on MRI. The middle asterisk had encasement of 3 segments (A1, ACom, and A2) of the anterior cerebral artery. MRI = magnetic resonance imaging.
reconstruction. The remainder were spread over the rest of the series. No identifiable preoperative or tumor-related factors enabled prediction of the likelihood of a leak. A few reconstruction preferences were found to decrease the rate of CSF leak. One was the use of the Hadad flap, which appeared to improve postoperative crusting/healing and showed a trend of decreasing the chance of a CSF leak. The use R (Integra Life Sciences Holdings Corporation, of Duragen Plainsboro, NJ) in the skull-base reconstruction also decreased the rate of postoperative CSF leak when used as an intracranial extradural underlay graft. Figure 4 shows the difference in CSF leak rate in two institutions using similar techniques but one hospital having access to the synthetic dural substitute. During statistical analysis, the Fisher’s exact test showed that use of Duragen during skullbase reconstruction in our series decreased the CSF leak rate significantly (p = 0.035). All 4 patients who required an additional trip to the operating theatre had their defects reexplored and re-repaired in a similar fashion. This involved carefully taking down the Hadad flap to precisely identify the site of the leak, without compromising the flap’s vasR was used cular pedicle. An intracranial graft of Duragen in one case, while the remaining 3 cases were repaired with tensor fascia lata. Caution was taken to avoid posterior displacement of the graft and that all corners were covered. Eight patients (22%) experienced other major complications, highlighting the high-risk nature of this surgery. Intracranial bleeds occurred during the postoperative period in 2 patients requiring return to theatre for evacuation. Both were treated successfully without further sequelae. Another patient with longstanding recurrent disease with multiple open craniotomy attempts underwent endoscopic debulking and postoperatively required prolonged intuba-
tion, subsequent tracheostomy, and finally a gastric feeding tube (g-tube) prior to discharge. Three patients suffered a prolapsed meningoencephalocele in the postoperative period. Two of these patients had a sufficiently large enough prolapse to benefit from a titanium mesh graft during their second repair. The other was a patient with multiple comorbidities including obesity, chronic smoking, and a chronic cough. In addition to prolapse, this patient suffered from a CSF leak and meningitis, which may also have been related to the comorbidities. With reoperation as well as IV antibiotics, this patient eventually healed well with no further leak or infection. Neither of the other 2 patients with prolapsed meningoencephaloceles had CSF leaks. Prior to use of the mid-roof ligation of the anterior and posterior ethmoidal artery technique, one patient had retraction of an anterior ethmoidal artery with subsequent intraorbital hematoma. Fortunately this was identified immediately and was managed with rapid endoscopic orbital decompression without further orbital sequelae. Minor nasal morbidity such as crusting was noticed by approximately 20% of patients and this typically responded to toileting and regular saline douching. Two patients had minor nasal infections requiring in-office debridement, an extra course of antibiotics, and a return office visit to ensure resolution. There were no intraoperative or immediate perioperative (within 1 month) mortalities. However, 2 patients passed away within 1 year of surgery. The patient that had undergone tracheostomy and g-tube (mentioned four paragraphs above) subsequently returned to the hospital for decreased level of consciousness, g-tube infection, Clostridium difficile infection, and this cascade of events led to the patient’s death approximately 3 months after the patient’s last
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FIGURE 4. Graph depicting our team’s overall CSF leak rate over time. The addition of the Hadad flap in late 2006 significantly lowered the CSF leak rate,
R R (Duragen was not available at the New Zealand site during the duration of the study and with additional stratification based upon availability of Duragen R significantly lowered the CSF leak rate in our series (p = 0.0353). therefore served as an internal control). A Fisher’s exact test showed that use of Duragen CSF = cerebrospinal fluid.
debulking procedure. The second mortality was a 52-yearold female with a large lateral clinoidal meningioma who had previously undergone an open left orbito-zygomatic Kawase approach prior to her endoscopic debulking. Although the debulking was successful with relief of her preoperative leg weakness, she was found deceased at home 6 weeks after her surgery. At postmortem, a hypertensive intracranial bleed into her tumor bed was thought to be the cause of her sudden death. No pseudoaneurysm or other vascular abnormality was identified.
Discussion Intranasal endoscopic resection of meningiomas has continued to evolve as the trend to address these tumors has shifted toward endoscopic resection. In this series, the original enthusiasm to tackle all skull-base tumors endoscopically has been tempered with experience. We believe that thorough preoperative clinical and radiological evaluation of each patient is important. The size, location of the tumor, and the degree of surrounding brain edema need to be considered when deciding on the best approach. From analysis of our series we found that tumor encasement of major vessels and capsular invasion of the tumor into the brain were the main factors influencing the length of surgery. Classification of tumor location is important for accurate representation of data in the literature. Olfactory groove meningiomas, tuberculum sellae meningiomas, and posterior fossa meningiomas all require different exposures and present a range of different challenges for the surgeons. In addition we found that olfactory groove tumors with anterior extension up to or past the anterior ethmoidal artery needed a frontal drill-out for access. For this reason, we categorized tumor locations into the following select
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FIGURE 5. (A) In our series there was one true subfrontal meningioma (center anterior to the cribriform plate). (B) There were 9 olfactory groove meningiomas with extension up to or anterior to the anterior ethmoidal artery (arrow). (C) There were 4 olfactory groove meningiomas that did not reach the anterior ethmoidal artery. (D) Twelve planum/jugum sphenoidale meningiomas. (E) Seven tuberculum sellae tumors. (F) One true clival tumor. Not pictured: 3 clinoidal meningiomas (found lateral to the midline). Arrow depicts anterior ethmoidal artery, tumors reaching this point (A and B) require a frontal drillout for access.
groups: subfrontal/olfactory groove, planum/jugum sphenoidale, tuberculum sellae, clinoidal, and clival (Fig. 5). The term “subfrontal” must be used with caution as most anterior skull-base tumors lie beneath the frontal lobes of the brain. Most “subfrontal” meningiomas are likely anterior olfactory groove tumors. If the center of a tumor was more anterior than the tip of the olfactory nerve, it was considered “subfrontal.” If the meningioma was centered over the cribriform plate with extension anteriorly beneath the frontal lobe of the brain, these were considered
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FIGURE 6. (A) Sagittal T2-weighted MRI showing significant brain edema with loss of the arachnoid plane superiorly. The decision was made to approach this tumor with an open craniotomy technique (therefore not included in our series). (B) Tumor dimensions were 4.96 cm × 4.0 cm × 3.16 cm (62.7 cm3 ) and total operative time was 7 hours 14 minutes. This open approach took less time when compared to the endoscopic approach to similarly sized tumors by the same surgeon, which averaged 12 hours 15 minutes. MRI = magnetic resonance imaging.
olfactory groove tumors. Caution was taken to determine the relation to the anterior ethmoidal artery, as mentioned in Figure 5. The majority of meningiomas in this study were midline or near midline. Three of the more posterior tumors were truly lateralized over the clinoidal region and were therefore categorized as such. This series suggests that as experience grows, the rate of complications and overall operative time decreases. The duration of surgery, especially for tumors less than 4 cm, tapered after about 7 cases (from an average of 8 hours 15 minutes to 5 hours 41 minutes). In addition, our rate of CSF leaks decreased. This further improved after the impleR as an intracranial underlay graft. mentation of Duragen Interestingly, the majority of CSF leaks occurred anteriorly in patients in whom the crista galli had been removed and
the falx cerebri had required transection. In one example, after a subfrontal meningioma was removed, the leak was found at the most anterior aspect of the skull-base defect. The cut edge of the falx appears to have prevented the anterior end of the underlay graft from been tucked under the anterior edge of the skull-base defect. It also suggests that gravity plays a role in postoperative healing and that placement of the packing may displace grafts posteriorly. From our experience, certain tumors should alert the skull-base team to review the feasibility and appropriateness of endoscopic resection. Tumors with volume greater than 60 cm3 or with an average diameter greater than 4 cm in which the case is suspected to take excessive number of hours (due to loss of arachnoid plane, encasement of major vessels, or adherence of the tumor to the brain with subsequent cerebral edema) should be considered for an external approach (Fig. 6). However, even with this philosophy, certain factors may push the skull-base team to decide to perform an endoscopic resection in light of the tumor size or predicted duration of the procedure. These factors include a tumor that displaces vital structures superiorly or a tumor that is midline and posterior where additional morbidity may be expected from an open approach. Certain palliative or tumor debulking procedures also may favor an endoscopic approach; such is the case when an open procedure is contraindicated. Compared to prior publications, which identified the feasibility of resecting skull-base meningiomas via an endoscopic approach, the current study assumes feasibility and concentrates on the case selection, complications, and pitfalls of the procedure in order to improve future outcomes. Although an exact size of tumor to be more appropriate for an open approach will vary for each surgical team, it likely lies somewhere between 30 and 60 cm3 . Tumors in this size range repeatedly required greater than 10 hours to complete and may have been more rapidly and effectively removed via an open approach. A univariate linear regression analysis of our data showed a significant addition to operative time with each incremental increase in tumor volume (Fig. 7). A similarly sized tumor with a diameter of >4 cm approached open may take as much as twice the operative time if approached endoscopically. Considering the advantages of an endoscopic approach, these have to be weighed against the additional operative time that may be added. In the end it is the skull-base team’s duty to perform whichever surgery will achieve the best results, regardless of the hours spent performing the surgery. The decrease in frontal lobe retraction and other benefits of the endoscopic approach is weighed against the increase in operating time found in larger tumors with surrounding brain edema. Considering the complexity of the surgery, complications are inevitable even in the hands of experienced surgeons and so all patients should be counseled appropriately and extensively preoperatively. Particular attention should be paid to patients with large tumors encasing critical structures, those with significant medical comorbidities, and patients
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FIGURE 7. The average operating time for all 37 cases in the series was 6 hours 11 minutes. This univariate linear regression graph depicts the number of hours added to the average operating time based on tumor volume. The asterisk (*) marks a volume of >60 cm3 , with a p value of
Update on endoscopic endonasal resection of skull base meningiomas Joseph Brunworth, MD1 , Vikram Padhye, MBBS2 , Ahmed Bassiouni, MBBCh2 , Alkis Psaltis, MBBS, PhD, FRACS2 , Stephen Floreani, MBBS, FRACS2 , Simon Robinson, MBChB, FRACS3 , Stephen Santoreneos, MBBS, FRACS4 , Nick Vrodos, MBBS, FRACS4 , Andrew Parker, MBBS, FRACS5 , Agadha Wickremesekera, MBChB, FRACS, MD5 and Peter-John Wormald, MBChB, FCS, FRCS, FRACS2
Background: The objective of this work was to report success rates as well as potential obstacles in transnasal endoscopic resection of anterior skull base meningiomas. Methods: The study design was a case series with chart review at tertiary referral centers in South Australia and New Zealand. The patients were 37 consecutive patients who underwent endoscopic resection of skull-base meningiomas between 2004 and 2013. Review of patient charts and operative details were performed. Outcomes including complications are reported. Results: Eighty-four percent of patients were women. There were 28 primary and 9 revision cases. Tumor locations were as follows: 14 olfactory groove/subfrontal; 12 planum/jugum sphenoidale; 7 tuberculum sellae; 3 clinoidal; and 1 clival. Vision change was the most common presenting symptom. Mean tumor volume was 33.68 cm3 , mean diameter was 2.78 cm. Average operating times decreased with an initial learning curve and then plateaued. Primary tumors larger than 60 cm3 took an average of 10 hours to resect. Gross total removal was achieved in 29 patients. There were no perioperative deaths. Two deaths occurred within 1 year of surgery. Postoperative cerebrospinal fluid (CSF) leaks occurred in 13 patients. Seventy-five percent of patients presenting with visual loss reported visual
1 Department
of Otolaryngology, St. Louis University Hospital, St. Louis, MO; 2 Department of Otolaryngology, Queen Elizabeth Hospital, Woodville South, SA, Australia; 3 Department of Otolaryngology, Wellington Hospital, Wellington, New Zealand; 4 Department of Neurosurgery, Royal Adelaide Hospital, Adelaide, SA, Australia; 5 Department of Neurosurgery, Wellington Hospital, Wellington, New Zealand Correspondence to: Joseph Brunworth, MD, St. Louis University Hospital, Dept of Otolaryngology, 6th Floor, Desloge Towers, 3635 Vista Ave, St. Louis, MO 63110; e-mail: [email protected] Potential conflict of interest: Although not directly related to this study, Peter J. Wormald receives royalties from Medtronic ENT and is a consultant for NeilMed. The remaining authors have no conflicts of interest. Received: 28 August 2014; Revised: 16 October 2014; Accepted: 30 October 2014 DOI: 10.1002/alr.21457 View this article online at wileyonlinelibrary.com.
improvement. Of the 29 patients considered to have had complete resection at surgery, one was found to have residual disease on a postoperative magnetic resonance imaging (MRI) and another one later developed radiological evidence of recurrence. Conclusion: Using a 2-team approach, meningiomas of the skull base were successfully removed via an intranasal endoscopic technique. Although complete resection is typically possible even with large tumors, the lengthy resection required time for tumors larger than 60 cm3 (diameter ࣙ4 cm) may obviate some of the advantages of this approach. The rate of postoperative CSF leak decreases when a synthetic dural substitute is added but does not apC 2014 ARS-AAOA, LLC. proach zero.
Key Words: intranasal; endoscopic; anterior; skull base; meningioma; endonasal resection; olfactory groove; anterior cranial fossa; subfrontal How to Cite this Article: Brunworth J, Padhye V, Bassiouni A, et al. Update on endoscopic endonasal resection of skull base meningiomas. Int Forum Allergy Rhinol. 2015;5:344–352.
T
he intimate relationship between anterior skull-base meningiomas and the surrounding neurovascular structures of the brain makes their removal a surgical challenge. With the exception of infrequent cases that have more aggressive histologic features, the majority of these tumors exhibit a slow growth pattern and have a low chance of recurrence if complete resection is achieved.1–4 The challenges encountered during surgery coupled with the potential for highly successful outcomes makes this an exciting frontier for surgeons and for the further development of the field.1, 5 The traditional approach to these tumors entails a craniotomy and often requires a degree of frontal lobe retraction for access.6 Even with utmost care, such retraction has been implicated in changes to the disposition of postoperative patients.6–9 Other disadvantages of this invasive approach include bone flap complications
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and cosmetic deformities.10, 11 With advances in endoscopic surgical instrumentation and techniques, the intranasal endoscopic removal of meningiomas poses an attractive alternative, circumventing the need for an external incision and frontal lobe retraction. In addition, as many of these tumors have an intimate relationship to the skull base, this more direct inferior approach afforded endonasally may reduce the need to cross neurovascular structures.1, 12–17 Although endoscopic techniques offer potential advantages, such surgery is not without its challenges and complications. As more institutions convert from traditional open craniotomy techniques to the minimally-invasive intranasal endoscopic route, reporting success rates as well as identifying potential complications becomes essential. This review reports our institution’s experience with the endoscopic resection of meningiomas.
Patients and methods Data collection A retrospective chart review was performed on all consecutive patients undergoing purely endoscopic intranasal approaches to anterior skull-base meningiomas from 2004 to 2013 at the South Australia Endoscopic Skull Base Unit (SAES) and Wellington Skull Base Units. A total of 37 patients with anterior skull-base meningiomas were resected using a wholly intranasal endoscopic approach and were included in the study. The Central Northern Adelaide Health Service Ethics of Human Research Committee granted approval of this study. Demographic, clinical, and tumor information was obtained via review of patients’ charts, magnetic resonance imaging (MRI), histology reports, operative notes, and intraoperative videos recorded for all cases. Tumor dimensions including area (cm2 ) and volume (cm3 ) were obtained via MRI measurements in all planes. The extent of resection was determined from operative notes and correlated with the intraoperative videos and postoperative histopathology reports. Complications were noted in the patients’ charts and are comprehensively detailed below. Patients who underwent tumor debulking when complete resection was not considered feasible are reported as residual rather than recurrent tumors and are specified as such.
Surgical method Preparation All patients were discussed preoperatively at our bimonthly skull-base meeting to ensure all surgeons were in agreement with the plan of care. Patients were prepped using a sterile technique including half-strength Betadine for facial prep and separate sterile fields for abdominal or thigh graft harvesting sites. Image guidance (StealthStation Medtronic Surgical Technologies, Jacksonville, FL) was used during all cases, merging the patient’s preoperative computed tomog-
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raphy (CT) with their MRI so that both imaging modalities could be used intraoperatively. Preoperative injection was performed with local anesthetic (2 mL of 2% lignocaine with 1:80,000 adrenaline) followed by placement of vasoconstrictive neuropatties (2 mL of 10% cocaine, 2 mL of 1:1000 adrenaline, and 2 mL of 9% saline). Reverse Trendelenburg and elevation of the head of bed was combined to a total of approximately 30 degrees. An indwelling catheter, large bore intravenous (IV) access, arterial line, and appropriate anesthetic monitors were placed before commencing surgery. Prophylactic antibiotics and deep venous thrombosis (DVT) compression stockings and sequential suppression devices were placed. In no cases was a prophylactic lumbar drain placed.
Surgical approach Surgeries were performed using a 2-team binostril endonasal technique. In all cases, the otolaryngology team performed the initial surgical approach. Septoplasty was performed if deemed necessary for access. A pedicled nasoseptal flap as first described by Hadad-Bassagasteguy was then raised and stored in the ipsilateral nasopharynx or maxillary sinus for later use in the reconstruction of the skull-base defect.18 The longest and broadest possible flap was harvested to ensure adequate extension over the skullbase defect. This flap was obtained early in the procedure to ensure that the posterior septal artery was carefully preserved within the flap and not injured during subsequent sphenoidotomy work. In rare cases of large defects, bilateral Hadad flaps were harvested and stored. In cases where only one flap was raised, a contralateral reverse rotation flap was used to cover the exposed septal cartilage at the donor site (Fig. 1). The subsequent degree of sinus surgery performed largely depended on the location of the tumor. In general, bilateral middle meatal antrostomies, total sphenoethmoidectomies, and frontal sinusotomies were performed in all cases to augment surgical access, allow identification of vital structures (skull base, orbit, orbital apex, carotid artery, and optic nerve), and reduce the risk of iatrogenic sinusitis. Additional procedures were performed according to tumor location. Patients with subfrontal tumors or tumors with extension anterior to the anterior ethmoidal artery had an endoscopic modified Lothrop/Draf 3 procedure performed (Fig. 2). All clival, clinoidal, tuberculum sellae, and planum/jugum sphenoidale patients had wide sphenoidotomies and excision of the superior turbinates for access. Upon clearance of all skull-base partitions, vascular control was gained of the anterior and posterior ethmoid arteries. Identification and ligation of these vessels was achieved at the midpoint of the ethmoidal roof rather than at their lateral entrance to minimize the risk of vessel retraction into the orbit and subsequent orbital hematoma.12 At this point, circumferential bony osteotomies were performed with the skull-base drill (3 mm skull base or Stylus coarse diamond bur; Medtronic Surgical Technologies, Jacksonville, FL) to
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FIGURE 1. Reverse septal flap. (A) Dotted line represents intended pedicled septal flap with posterior septal branch of the sphenopalatine artery providing the blood supply. (B) Pedicled Hadad flap tucked into ipsilateral choana. Dotted line represents intended cut to be made on the medial surface of the contralateral septal mucosa. (C) The contralateral septal mucosa is then brought forward to cover the remaining anterior septum and is sutured into place using a standard quilting stitch. R (Integra Lifesciences, trasonic Surgical Aspirator (CUSA) York, PA) can be used, depending on surgeon preference. In this manner, complete tumor resection with preservation of surrounding vasculature can typically be achieved with clearance confirmed through the use of angled endoscopes.
Skull base reconstruction
FIGURE 2. Coronal MRI at the level of the anterior ethmoidal artery showing tumor extends further anteriorly. This patient’s approach would include a frontal drillout (endoscopic modified Lothrop/Draf 3 procedure) to ensure adequate access anteriorly. MRI = magnetic resonance imaging.
expose the underlying dura without penetration. At this point in the dissection, the 2-surgeon technique was used. The endoscope was held by the otolaryngologist allowing the neurosurgeon to use both hands for the tumor resection. We have found that more room can be provided for surgical instrumentation by positioning the endoscope in a superolateral position (on the patient’s right side) and maintaining an off-centered endoscopic view. Although a 0-degree endoscope is used for the majority of the procedure, angled scopes can also be used at various times if further visualization is needed during the dissection. Bipolar cautery is typically applied to the dura prior to its incision to seal any dural venous vessels. Once the dura is incised, the tumor is debulked from inside out, collapsing the tumor and allowing the tumor edges to be brought into the involuted central area. This is generally considered a safer zone of dissection and allows excellent visualization of the arachnoid plane that can then be carefully teased from the tumor. Within this safer zone of dissection, additional R ultrasonic aspisurgical instruments such as the Sonopet rator (Stryker Corp., Kalamazoo, MI) or the Cavitron Ul-
After tumor removal, attention is turned toward repair of the skull-base defect. This is performed in a multilayered fashion, can be varied in technique19 , and is done in a manner most appropriate for the defect at hand. Most commonly, an underlay graft is placed within the cranial vault. This can be of autologous origin such as tensor fasR (Intecia lata or a synthetic material such as Duragen gra Life Sciences Holdings Corporation, Plainsboro, NJ), which we most commonly used in our series. Our experience with larger skull base defects and the possibility of a degree of frontal lobe collapse has resulted in us now reinforcing the skull-base repair with a rigid support in the form of autologous septal cartilage or a mesh titanium plate (Medtronic Surgical Technologies, Jacksonville, FL). For these larger defects, we also add a second overlay support R . The in the form of fascia lata or second layer of Duragen vascularized septal flap is then rotated into place, ensuring that the mucosal surface is facing intranasally. Caution is taken to circumferentially sit the flap directly onto bone to facilitate graft adherence. Following this, small pieces of R mesh (Ethicon, Somersville, NJ) are placed cirSurgicel cumferentially around the edges of the flap to seat the graft directly against the bone and prevent the edges from lifting when a tissue sealant such as DuraSealTM (Confluent R Surgical, Waltham, MA) is then applied. After Surgicel TM and DuraSeal have been applied, intranasal counter supR (Pfizer, New York City, port is achieved with Gelfoam NY) followed by bismuth iodoform paraffin paste (BIPP)soaked ribbon gauze (BIPP; Orion Labaratories, Balcatta, Australia). This gauze is kept in place for 7 days and removed in the clinic setting.
Follow-up Patients were extubated postoperatively and kept overnight in the intensive care unit for close neurological monitoring.
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Most patients had a CT scan on postoperative day 1 to confirm the reconstruction remained in correct position and that no significant intracranial air or bleeding had accumulated. After patients were cleared for discharge, follow-up was arranged with both the neurosurgical as well as otolaryngology teams. Nasal saline rinses were commenced upon removal of the BIPP-soaked ribbon gauze. Patients without unusual circumstances had a postoperative MRI at 3 months and yearly thereafter.
Results Demographic and clinical information Thirty-seven patients with anterior skull-base meningiomas undergoing solely intranasal endoscopic resection between 2004 and 2013 were identified and included in the study. Eighty-four percent (n = 31) were female, with an average age of 53 years. Visual change was the most common presenting symptom, described by 60% of patients (22/37). Most commonly the visual change correlated with optic chiasm or tract compression. The second most common presenting symptom was headache (16%; 6/37). Other presenting symptoms included epistaxis, seizures, fatigue, anosmia, or a combination of the previously mentioned symptoms.
Tumor characteristics Tumor location included the following: 14 olfactory groove/subfrontal, 12 planum/jugum sphenoidale, 7 tuberculum sellae, 3 clinoidal, and 1 clival. Tumor size varied from 1.26 (1.5 × 1.2 × 0.7) cm3 in volume up to the largest measuring 130.5 (5.8 × 5.0 × 4.5) cm3 . The mean volume of the tumors was 33.7 cm3 , with a mean size area of 9.9 cm2 (range, 1.6 to 29 cm2 ), and mean diameter of 2.78 cm (range, 0.7 to 5.8 cm).
Surgical statistics Twenty-eight were primary cases and 9 were revisions. Of the revision cases, 7 initially had open approaches and the remaining two had prior endonasal approaches.
Operative times Operative time ranged from 2 hours 55 minutes to 12 hours 43 minutes. This was influenced by surgical experience, size of the tumor, preservation of an arachnoid plane at the brain/tumor interface, and the proximity and encasement of critical neurovascular structures. Operative times generally decreased with increasing surgical experience. The first 7 cases averaged 8 hours 15 minutes decreasing to an average of 5 hours 41 minutes thereafter. Large tumors, greater than 4 cm in diameter or more than 60 cm3 in volume, typically required over 10 hours to resect irrespective of surgical experience (Fig. 3). In only one instance was a primary tumor with a mean volume greater than 50 cm3 able to be resected in less than 7 hours. Preservation of the tumor/arachnoid plane also influenced resection time. If the arachnoid plane
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was preserved, the resection was rapid. In contrast, loss of this plane required meticulous dissection of each blood vessel off of the tumor, thereby increasing surgical time. An indication as to whether or not the arachnoid plane was likely to be preserved was the amount of brain edema seen at the interface between the tumor and the brain on the MRI scan. As a validated grading system for edema associated with tumors does not currently exist, we did not attempt to grade the extent of edema, but rather noted its presence or absence. Brain edema was noted in 7 of our cases. An additional time factor was encasement of the anterior cerebral arteries (found in 8 patients). In a number of cases there was encasement of the A1, ACom, and/or A2 sections of the anterior cerebral arteries. In these cases, careful dissection and preservation of the vessels added significantly to the operative time.
Extent of resection Gross total resection was achieved in 29 of the 37 patients (78.4%). Subtotal resection and tumor debulking were performed in 8 patients for whom total resection was not achievable without a high risk of significant morbidity and possible mortality. One-half of these were revision cases extending deep into the cranial vault or clinoid region with symptoms from mass effect in which debulking was required for deteriorating neurology. The others were scheduled for excision and found intraoperatively to be unsafe for complete resection due to tumor encased neurological structures or major blood vessels. A Fisher’s exact test showed a statistically significant increase in the chance for residual or recurrent disease when the tumor was shown to encase major blood vessels on preoperative imaging (p = 0.007). Of the revision cases, no distinguishing factors were identified in those patients with prior open procedures vs those with prior endoscopic procedures. In both groups, as in most revision cases, the planes tended to be more obscured and a slower, more meticulous dissection technique was warranted. Having a recurrence also increased the patient’s chance of incomplete resection on the second attempt as many of these cases were for tumor debulking and attempts at symptomatic improvement. All patients with incomplete resection were re-presented at tumor board for additional treatment options including observation, planned re-operation, radiotherapy, or other treatment modalities. Of the 9 revision cases in the series, 3 had already undergone radiotherapy prior to their revision surgery.
Complications In this series, the most common complication was postoperative cerebrospinal fluid (CSF) leak, requiring return to the operating theatre in 4 of 37 patients (11%). An additional 9 (24%) responded to lumbar drain alone. Of the CSF leaks recorded, 3 out of the first 4 procedures were affected, suggesting a steep learning curve for skull-base
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FIGURE 3. Graph depicting the initial learning curve (the first 7 cases averaging 8 hours 15 minutes), subsequent improved operating times (remaining cases averaging 5 hours 41 minutes). Cases marked with an asterisk (*) had an average diameter of 4.5 cm and average operating time of 12 hours 5 minute. These three were also identified to have edema and encasement of vasculature on MRI. The middle asterisk had encasement of 3 segments (A1, ACom, and A2) of the anterior cerebral artery. MRI = magnetic resonance imaging.
reconstruction. The remainder were spread over the rest of the series. No identifiable preoperative or tumor-related factors enabled prediction of the likelihood of a leak. A few reconstruction preferences were found to decrease the rate of CSF leak. One was the use of the Hadad flap, which appeared to improve postoperative crusting/healing and showed a trend of decreasing the chance of a CSF leak. The use R (Integra Life Sciences Holdings Corporation, of Duragen Plainsboro, NJ) in the skull-base reconstruction also decreased the rate of postoperative CSF leak when used as an intracranial extradural underlay graft. Figure 4 shows the difference in CSF leak rate in two institutions using similar techniques but one hospital having access to the synthetic dural substitute. During statistical analysis, the Fisher’s exact test showed that use of Duragen during skullbase reconstruction in our series decreased the CSF leak rate significantly (p = 0.035). All 4 patients who required an additional trip to the operating theatre had their defects reexplored and re-repaired in a similar fashion. This involved carefully taking down the Hadad flap to precisely identify the site of the leak, without compromising the flap’s vasR was used cular pedicle. An intracranial graft of Duragen in one case, while the remaining 3 cases were repaired with tensor fascia lata. Caution was taken to avoid posterior displacement of the graft and that all corners were covered. Eight patients (22%) experienced other major complications, highlighting the high-risk nature of this surgery. Intracranial bleeds occurred during the postoperative period in 2 patients requiring return to theatre for evacuation. Both were treated successfully without further sequelae. Another patient with longstanding recurrent disease with multiple open craniotomy attempts underwent endoscopic debulking and postoperatively required prolonged intuba-
tion, subsequent tracheostomy, and finally a gastric feeding tube (g-tube) prior to discharge. Three patients suffered a prolapsed meningoencephalocele in the postoperative period. Two of these patients had a sufficiently large enough prolapse to benefit from a titanium mesh graft during their second repair. The other was a patient with multiple comorbidities including obesity, chronic smoking, and a chronic cough. In addition to prolapse, this patient suffered from a CSF leak and meningitis, which may also have been related to the comorbidities. With reoperation as well as IV antibiotics, this patient eventually healed well with no further leak or infection. Neither of the other 2 patients with prolapsed meningoencephaloceles had CSF leaks. Prior to use of the mid-roof ligation of the anterior and posterior ethmoidal artery technique, one patient had retraction of an anterior ethmoidal artery with subsequent intraorbital hematoma. Fortunately this was identified immediately and was managed with rapid endoscopic orbital decompression without further orbital sequelae. Minor nasal morbidity such as crusting was noticed by approximately 20% of patients and this typically responded to toileting and regular saline douching. Two patients had minor nasal infections requiring in-office debridement, an extra course of antibiotics, and a return office visit to ensure resolution. There were no intraoperative or immediate perioperative (within 1 month) mortalities. However, 2 patients passed away within 1 year of surgery. The patient that had undergone tracheostomy and g-tube (mentioned four paragraphs above) subsequently returned to the hospital for decreased level of consciousness, g-tube infection, Clostridium difficile infection, and this cascade of events led to the patient’s death approximately 3 months after the patient’s last
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FIGURE 4. Graph depicting our team’s overall CSF leak rate over time. The addition of the Hadad flap in late 2006 significantly lowered the CSF leak rate,
R R (Duragen was not available at the New Zealand site during the duration of the study and with additional stratification based upon availability of Duragen R significantly lowered the CSF leak rate in our series (p = 0.0353). therefore served as an internal control). A Fisher’s exact test showed that use of Duragen CSF = cerebrospinal fluid.
debulking procedure. The second mortality was a 52-yearold female with a large lateral clinoidal meningioma who had previously undergone an open left orbito-zygomatic Kawase approach prior to her endoscopic debulking. Although the debulking was successful with relief of her preoperative leg weakness, she was found deceased at home 6 weeks after her surgery. At postmortem, a hypertensive intracranial bleed into her tumor bed was thought to be the cause of her sudden death. No pseudoaneurysm or other vascular abnormality was identified.
Discussion Intranasal endoscopic resection of meningiomas has continued to evolve as the trend to address these tumors has shifted toward endoscopic resection. In this series, the original enthusiasm to tackle all skull-base tumors endoscopically has been tempered with experience. We believe that thorough preoperative clinical and radiological evaluation of each patient is important. The size, location of the tumor, and the degree of surrounding brain edema need to be considered when deciding on the best approach. From analysis of our series we found that tumor encasement of major vessels and capsular invasion of the tumor into the brain were the main factors influencing the length of surgery. Classification of tumor location is important for accurate representation of data in the literature. Olfactory groove meningiomas, tuberculum sellae meningiomas, and posterior fossa meningiomas all require different exposures and present a range of different challenges for the surgeons. In addition we found that olfactory groove tumors with anterior extension up to or past the anterior ethmoidal artery needed a frontal drill-out for access. For this reason, we categorized tumor locations into the following select
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FIGURE 5. (A) In our series there was one true subfrontal meningioma (center anterior to the cribriform plate). (B) There were 9 olfactory groove meningiomas with extension up to or anterior to the anterior ethmoidal artery (arrow). (C) There were 4 olfactory groove meningiomas that did not reach the anterior ethmoidal artery. (D) Twelve planum/jugum sphenoidale meningiomas. (E) Seven tuberculum sellae tumors. (F) One true clival tumor. Not pictured: 3 clinoidal meningiomas (found lateral to the midline). Arrow depicts anterior ethmoidal artery, tumors reaching this point (A and B) require a frontal drillout for access.
groups: subfrontal/olfactory groove, planum/jugum sphenoidale, tuberculum sellae, clinoidal, and clival (Fig. 5). The term “subfrontal” must be used with caution as most anterior skull-base tumors lie beneath the frontal lobes of the brain. Most “subfrontal” meningiomas are likely anterior olfactory groove tumors. If the center of a tumor was more anterior than the tip of the olfactory nerve, it was considered “subfrontal.” If the meningioma was centered over the cribriform plate with extension anteriorly beneath the frontal lobe of the brain, these were considered
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FIGURE 6. (A) Sagittal T2-weighted MRI showing significant brain edema with loss of the arachnoid plane superiorly. The decision was made to approach this tumor with an open craniotomy technique (therefore not included in our series). (B) Tumor dimensions were 4.96 cm × 4.0 cm × 3.16 cm (62.7 cm3 ) and total operative time was 7 hours 14 minutes. This open approach took less time when compared to the endoscopic approach to similarly sized tumors by the same surgeon, which averaged 12 hours 15 minutes. MRI = magnetic resonance imaging.
olfactory groove tumors. Caution was taken to determine the relation to the anterior ethmoidal artery, as mentioned in Figure 5. The majority of meningiomas in this study were midline or near midline. Three of the more posterior tumors were truly lateralized over the clinoidal region and were therefore categorized as such. This series suggests that as experience grows, the rate of complications and overall operative time decreases. The duration of surgery, especially for tumors less than 4 cm, tapered after about 7 cases (from an average of 8 hours 15 minutes to 5 hours 41 minutes). In addition, our rate of CSF leaks decreased. This further improved after the impleR as an intracranial underlay graft. mentation of Duragen Interestingly, the majority of CSF leaks occurred anteriorly in patients in whom the crista galli had been removed and
the falx cerebri had required transection. In one example, after a subfrontal meningioma was removed, the leak was found at the most anterior aspect of the skull-base defect. The cut edge of the falx appears to have prevented the anterior end of the underlay graft from been tucked under the anterior edge of the skull-base defect. It also suggests that gravity plays a role in postoperative healing and that placement of the packing may displace grafts posteriorly. From our experience, certain tumors should alert the skull-base team to review the feasibility and appropriateness of endoscopic resection. Tumors with volume greater than 60 cm3 or with an average diameter greater than 4 cm in which the case is suspected to take excessive number of hours (due to loss of arachnoid plane, encasement of major vessels, or adherence of the tumor to the brain with subsequent cerebral edema) should be considered for an external approach (Fig. 6). However, even with this philosophy, certain factors may push the skull-base team to decide to perform an endoscopic resection in light of the tumor size or predicted duration of the procedure. These factors include a tumor that displaces vital structures superiorly or a tumor that is midline and posterior where additional morbidity may be expected from an open approach. Certain palliative or tumor debulking procedures also may favor an endoscopic approach; such is the case when an open procedure is contraindicated. Compared to prior publications, which identified the feasibility of resecting skull-base meningiomas via an endoscopic approach, the current study assumes feasibility and concentrates on the case selection, complications, and pitfalls of the procedure in order to improve future outcomes. Although an exact size of tumor to be more appropriate for an open approach will vary for each surgical team, it likely lies somewhere between 30 and 60 cm3 . Tumors in this size range repeatedly required greater than 10 hours to complete and may have been more rapidly and effectively removed via an open approach. A univariate linear regression analysis of our data showed a significant addition to operative time with each incremental increase in tumor volume (Fig. 7). A similarly sized tumor with a diameter of >4 cm approached open may take as much as twice the operative time if approached endoscopically. Considering the advantages of an endoscopic approach, these have to be weighed against the additional operative time that may be added. In the end it is the skull-base team’s duty to perform whichever surgery will achieve the best results, regardless of the hours spent performing the surgery. The decrease in frontal lobe retraction and other benefits of the endoscopic approach is weighed against the increase in operating time found in larger tumors with surrounding brain edema. Considering the complexity of the surgery, complications are inevitable even in the hands of experienced surgeons and so all patients should be counseled appropriately and extensively preoperatively. Particular attention should be paid to patients with large tumors encasing critical structures, those with significant medical comorbidities, and patients
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FIGURE 7. The average operating time for all 37 cases in the series was 6 hours 11 minutes. This univariate linear regression graph depicts the number of hours added to the average operating time based on tumor volume. The asterisk (*) marks a volume of >60 cm3 , with a p value of
