Letter to the Editor: The endoscopic endonasal approach in the treatment of olfactory groove meningiomas

View More View Less
  • Wexner Medical Center, The Ohio State University College of Medicine, Columbus, OH
Full access

If the inline PDF is not rendering correctly, you can download the PDF file here.

TO THE EDITOR: We read with interest the article by Banu et al.1 (Banu MA, Mehta A, Ottenhausen M, et al: Endoscope-assisted endonasal versus supraorbital keyhole resection of olfactory groove meningiomas: comparison and combination of 2 minimally invasive approaches. J Neurosurg 124:605–620, March 2016).

The role of the endoscopic endonasal approach (EEA) in the treatment of olfactory groove meningiomas is controversial and has been a matter of discussion in the current literature. Various surgical approaches have been advocated to resect these tumors, among which the subfrontal (unilateral or bilateral) and pterional approaches are the most popular.

Supporters of transcranial approaches highlight the advantages of the faster surgical route, better vascular control, potential to preserve olfactory function, and lower rates of postoperative CSF leakage. Conversely, defenders of the EEA emphasize the lack of retraction and less manipulation of the brain, early tumor devascularization, and maximal resection of the base of the skull that may be infiltrated by the meningioma. Both approaches have caveats to achieve a complete tumor resection.

In the midst of this debate, Banu et al.1 compared the EEA with the supraorbital keyhole approach (microsurgical with endoscope assistance) and a combined approach applying both techniques (i.e., “above-and-below” approach) for resection of olfactory groove meningiomas. They reviewed a prospectively acquired database of minimal access surgeries performed between 2004 and 2014 where 19 patients were classified according to operative technique. Tumors were assessed based on the Mohr radiological classification and the presence of the lion's mane sign. Adequacy of the resection was ascertained using volumetric analysis of postoperative MR images.

The authors reported that their selection criteria evolved over time. Initially, an EEA was attempted in all patients with olfactory groove meningiomas that did not extend laterally more than 1 cm beyond the lamina papyracea. A supraorbital keyhole approach was adopted after obtaining suboptimal results with respect to the extent of resection (EOR), closure of the skull base defect, and olfactory function. In their latter experience, patients with tumors extending through the cribriform plate, which required skull base repairs that could not be performed through a transcranial approach, the EEA was used in combination with a transcranial approach, concurrently or as a staged surgery. Therefore, as a result of their change in selection criteria, the authors rarely perform an independent EEA for olfactory groove meningiomas. They conclude that the limitations of an EEA might outweigh the benefits in the treatment of olfactory meningiomas, and they advocate the use of the supraorbital eyebrow mini-craniotomy with endoscopic assistance due to the greater EOR with fewer associated complications.

This is an interesting report that deserves the consideration of all skull base surgeons interested in this subject. However, we believe that there are factors that may have influenced the approach selection and analysis of the outcomes that were not highlighted by the authors. First, from a statistical viewpoint, the data are insufficient to draw dogmatic statements regarding the role of the EEA in the treatment of olfactory groove meningiomas.

Furthermore, early in their experience the authors attempted an EEA in all patients with olfactory groove meningioma extending no more than 1 cm lateral to the lamina papyracea. Their series extends back to 2004, when EEA was available at very few centers worldwide. Surgical technology and customized instrumentation, as well as approach, resection, and reconstruction techniques, have undergone significant progress. Endoscopic surgical groups have achieved experience with increased improvement and refinement of patient selection. Therefore, one could attribute the reported suboptimal outcomes on their lack of experience or the so-called learning curve. We have to ask ourselves if the authors' extent of tumor resection and complications rates would be different under current circumstances and after 10 years of additional experience.

It is a well-known fact, and reinforced in the paper, that the risk of residual tumor laterally over the orbits is a limitation of the EEA, and, therefore, its presence could compromise EOR. Nevertheless, we are puzzled by the fact that most of the residual tumors, following an EEA, were located at median areas (i.e., cribriform plate, ethmoid sinuses, planum sphenoidale, and crista galli). Similarly, residual tumors for the “above-and-below” group were located at the planum sphenoidale and lamina papyracea. These locations are readily accessed as part of the endonasal approach. This indicates that the outcomes regarding the EOR are not necessarily related to limitations of the EEA.

Additionally, in these cases of tumors extending through the cribriform plate, in which the authors opted for the “above-and-below” approach, the EEA was performed either concomitantly or after a transcranial approach in 5 of 6 cases. We wonder if any of these tumors could have been completely removed through an exclusively EEA.

Likewise, the aforementioned small number of patients is an important limitation of the study. Aside from the lack of statistical power, there are other weaknesses in the analysis. Case 1 in the EEA group, for example, could be considered an outlier, as its extremely low EOR of 40.2%, significantly decreases the EOR average for this group (6 cases).

In adequately selected patients, the EEA yields superior surgical results in the management of other ventral median skull base tumors and has become a safe and reliable option in the armamentarium of skull base approaches. Improvement and development of surgical tools have reduced some of the limitations of the approach; for example, angled instrumentation has circumvented the limitation to resect tumors at the most anterior aspect of the skull base. Similarly, progressive refinements of the surgical techniques have improved the access and resection of tumors in this area; removal of the lamina papyracea allows the displacement of the orbital soft tissues, thus allowing the resection of tumors that extend beyond 1 cm lateral to the lamina. In our experience, as long as the meningioma does not have a dural attachment that extends superiorly at the level of the posterior table of the frontal sinus, or laterally over the orbital apex (where displacement of the orbital soft tissues is limited), it may be safely dissected and removed via an endoscopic endonasal route.

Similarly, the reconstruction of the most anterior region of the skull base defect has also improved through the use of a variety of multilayer techniques, including the development of pedicled endonasal flaps (first reported in 2006) and further refinements in the temporary bolster to support the reconstruction.

As for any other skull base approach, patient selection is critical for the success of an EEA. Nonetheless, one should recognize that patient selection is not only influenced by the histology and extent of the lesion, but also by the surgical team's experience, skills, and resources, as well as by the patient's comorbidities and preferences. Use of an EEA for olfactory groove meningiomas does have important limitations. Those of greater significance include the risk of anosmia in patients with adequate preoperative function, risk of hemorrhage or cerebrovascular accidents in patients with tumors that show vascular encasement, and the risk of residual tumor in patients with lateral or anterior dural attachments. Albeit important, these caveats do not eliminate the EEA as an alternative in adequately selected patients. In our opinion, in the presence of an experienced team with adequate institutional resources, the EEA remains as one of the main surgical approaches to manage olfactory groove meningiomas. One can maximize the advantages of the EEA with an unbiased and appropriate patient selection.

Furthermore, we believe that the EEA is suitable for a broader range of olfactory groove meningiomas than Banu et al.1 suggested. The ideal patient would be one with impaired olfaction and with a tumor that is not attached to the posterior wall of the frontal sinus and that does not extend beyond the meridian of the orbit or to the superolateral aspect of the optic canal (anterior clinoid). The size of the tumor does not seem to be a significant factor. Presence of sinonasal invasion is not mandatory in order to indicate an EEA. Conversely, vascular encasement is not an absolute contraindication, although it definitely compounds the difficulty and risks of the surgery.

In addition, the EEA offers supplementary value in the surgical management of giant olfactory groove meningiomas with significant bi–frontal lobe edema. In our experience, patients with these tumors are the ones who benefit from staged or combined procedures. Different from most “above-and-below” cases presented in the paper by Banu et al.,1 our strategy consists of an initial EEA procedure with the goal of debulking and devascularizing the tumor. This creates the possibility for tumor collapse and improvement of brain edema, thus facilitating a less traumatic dissection at a second stage, which can be through another EEA or an alternative transcranial approach.

In conclusion, each skull base approach and technique has advantages and limitations that must be weighted and considered when selecting the best treatment management for a particular patient. Endoscopic endonasal approaches represent an excellent alternative for the surgical management of the majority of olfactory groove meningiomas independently or in combination with open approaches. The use of EEAs for olfactory groove meningiomas must not be excluded based on the initial poor outcomes of a single surgical team.

References

1

Banu MA, , Mehta A, , Ottenhausen M, , Fraser JF, , Patel KS, & Szentirmai O, : Endoscope-assisted endonasal versus supraorbital keyhole resection of olfactory groove meningiomas: comparison and combination of 2 minimally invasive approaches. J Neurosurg 124:605620, 2016

  • Search Google Scholar
  • Export Citation

Disclosures

Dr. Carrau reports that he has received travel expenses to participate as faculty in a hands-on course from Medtronic.

View More View Less
  • Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, NY
Keywords:

Response

Dr. Beer-Furlan and colleagues present a thoughtful assessment of our paper and we thank them for taking the time to read and analyze our paper and provide their valuable opinions. We also thank the Journal of Neurosurgery for the opportunity to respond. We will first address each of the authors' comments and then provide some analysis of the published literature to support our perspective.

The first claim made is that, given the limited number of patients reported, there is not enough statistical power to make any dogmatic statements. We could not agree more. Our observations were meant to be food for thought to encourage further investigation and discussion in this area and to provide some data, rather than anecdotes, regarding outcomes of surgery for olfactory groove meningiomas using different approaches. The reviewers also correctly point out that the initial cases were done in 2004, at the beginning of our learning curve. There is no doubt that the technical abilities and decision making of our center have improved over time.1 However, during this same time period, we were also learning how to remove planum and tuberculum meningiomas, and, while our results continued to improve with respect to meningiomas in other locations, the results for olfactory groove meningiomas remained suboptimal.10 Moreover, we also embarked on a learning curve for the supraorbital craniotomy with endoscopic assistance and a learning curve was in effect for these cases as well, which we performed less frequently than endonasal cases.

The authors' main point to support their use of the EEA for olfactory groove meningiomas is that it has been shown to be superior to transcranial approaches for other pathologies. This seems like a weak argument, since an approach cannot be evaluated without the context of a specific pathology. While we agree that the endonasal approach has been shown to be better for other pathologies and have even published several articles supporting this claim,2–8 the same cannot be said for olfactory groove meningiomas, where the data from the literature show inferior results using the endonasal approach.7 The authors go on to recommend the endonasal approach based on their anecdotal unpublished experience. There is no question that the surgeons in Ohio are outstanding endonasal surgeons and that their results are likely as good as they can be for the endonasal approach. Nevertheless, until results are published and evaluated objectively, it is difficult to draw any conclusions. We have only the existing published results in the literature to go on and, absent any prospective randomized data, must rely on retrospective data with all its inherent biases.

The largest series of endonasal endoscopic resections of olfactory groove meningiomas published to date is a series of 50 patients operated on at the University of Pittsburgh Medical Center (UPMC), which was published in 2014.9 One could hardly argue that this group does not have adequate experience or technical expertise to perform this surgery in a highly skilled manner. In these patients, gross-total resection (GTR) was achieved in 30 of 50 patients (60%), the average length of surgery was 9 hours, and the average length of stay was 11 days; 36% of patients required more than 1 endonasal surgery to achieve their results, which further increases the amount of time in the operating room and hospital stays for each patient. Although Beer-Furlan et al. claim that size is not a significant factor in EOR, the group at UPMC clearly stated that size significantly limited EOR (p = 0.002). Moreover, complication rates were fairly high. Although a total complication rate is never reported, there were 44 complications, so the overall rate may have been 88%, including CSF leak (30%), deep venous thrombosis/pulmonary embolism (20%), sinusitis (10%), respiratory failure requiring tracheotomy (8%), ventriculoperitoneal shunt (6%), abscess formation (6%), seizure (4%), and stroke (2%). Moreover, while only 8 patients complained of anosmia before surgery, all 50 patients were clearly anosmic after surgery given the approach. As for the learning curve, the rate of GTR improved to 80% at the end of their series, but the introduction of the nasoseptal flap had no influence on CSF leaks, which remained at 30%.

Until other groups start to publish their results in large numbers, the series out of UPMC represents the best assessment of the results following endonasal endoscopic resection of olfactory groove meningiomas. A recent review of the literature showed that traditional craniotomy resulted in GTR rates of 92.8%.7 At some point we have to look closely at our results and decide whether an EEA truly offers the best possible outcome for our patients in this situation. As we clearly discussed in our paper, the endonasal approach will always have an important role to play in the management of olfactory groove meningiomas in selected cases. The real issue is whether it should be offered to all patients as the initial surgery of choice. We eagerly await the publication of additional large series of consecutive endonasal operations for olfactory groove meningiomas so that this discussion can continue.

References

  • 1

    Khan OH, , Anand VK, & Schwartz TH: Endoscopic endonasal resection of skull base meningiomas: the significance of a “cortical cuff” and brain edema compared with surgical experience and case selection in predicting morbidity and extent of resection. Neurosurg Focus 37:4 E7, 2014

    • Search Google Scholar
    • Export Citation
  • 2

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endonasal endoscopic versus transoral microscopic odontoid resection. Innov Neurosurg 1:3747, 2013

    • Search Google Scholar
    • Export Citation
  • 3

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: The endoscope-assisted ventral approach compared with open microscope-assisted surgery for clival chordomas. World Neurosurg 76:318327, 2011

    • Search Google Scholar
    • Export Citation
  • 4

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal compared with anterior craniofacial and combined cranionasal resection of esthesioneuro-blastomas. World Neurosurg 80:148159, 2013

    • Search Google Scholar
    • Export Citation
  • 5

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal compared with microscopic transsphenoidal and open transcranial resection of giant pituitary adenomas. Pituitary 15:150159, 2012

    • Search Google Scholar
    • Export Citation
  • 6

    Komotar RJ, , Starke RM, , Raper DM, , Anand VK, & Schwartz TH: Endoscopic endonasal versus open repair of anterior skull base CSF leak, meningocele, and encephalocele: a systematic review of outcomes. J Neurol Surg A Cent Eur Neurosurg 74:239250, 2013

    • Search Google Scholar
    • Export Citation
  • 7

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal versus open transcranial resection of anterior midline skull base meningiomas. World Neurosurg 77:713724, 2012

    • Search Google Scholar
    • Export Citation
  • 8

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic versus transsphenoidal microscopic and transcranial resection of craniopharyngiomas. World Neurosurg 77:329341, 2012

    • Search Google Scholar
    • Export Citation
  • 9

    Koutourousiou M, , Fernandez-Miranda JC, , Wang EW, , Snyderman CH, & Gardner PA: Endoscopic endonasal surgery for olfactory groove meningiomas: outcomes and limitations in 50 patients. Neurosurg Focus 37:4 E8, 2014

    • Search Google Scholar
    • Export Citation
  • 10

    Ottenhausen M, , Banu M, , Placantonakis DG, , Tsiouris AJ, , Khan OH, , Anand VK, & Schwartz TH: Endoscopic endonasal resection of suprasellar meningiomas: the importance of case selection and experience in determining extent of resection, visual improvement and complications. World Neurosurg 83:442449, 2014

    • Search Google Scholar
    • Export Citation

If the inline PDF is not rendering correctly, you can download the PDF file here.

Contributor Notes

INCLUDE WHEN CITING Published online February 5, 2016; DOI: 10.3171/2015.9.JNS152215.

  • 1

    Banu MA, , Mehta A, , Ottenhausen M, , Fraser JF, , Patel KS, & Szentirmai O, : Endoscope-assisted endonasal versus supraorbital keyhole resection of olfactory groove meningiomas: comparison and combination of 2 minimally invasive approaches. J Neurosurg 124:605620, 2016

    • Search Google Scholar
    • Export Citation
  • 1

    Khan OH, , Anand VK, & Schwartz TH: Endoscopic endonasal resection of skull base meningiomas: the significance of a “cortical cuff” and brain edema compared with surgical experience and case selection in predicting morbidity and extent of resection. Neurosurg Focus 37:4 E7, 2014

    • Search Google Scholar
    • Export Citation
  • 2

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endonasal endoscopic versus transoral microscopic odontoid resection. Innov Neurosurg 1:3747, 2013

    • Search Google Scholar
    • Export Citation
  • 3

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: The endoscope-assisted ventral approach compared with open microscope-assisted surgery for clival chordomas. World Neurosurg 76:318327, 2011

    • Search Google Scholar
    • Export Citation
  • 4

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal compared with anterior craniofacial and combined cranionasal resection of esthesioneuro-blastomas. World Neurosurg 80:148159, 2013

    • Search Google Scholar
    • Export Citation
  • 5

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal compared with microscopic transsphenoidal and open transcranial resection of giant pituitary adenomas. Pituitary 15:150159, 2012

    • Search Google Scholar
    • Export Citation
  • 6

    Komotar RJ, , Starke RM, , Raper DM, , Anand VK, & Schwartz TH: Endoscopic endonasal versus open repair of anterior skull base CSF leak, meningocele, and encephalocele: a systematic review of outcomes. J Neurol Surg A Cent Eur Neurosurg 74:239250, 2013

    • Search Google Scholar
    • Export Citation
  • 7

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic endonasal versus open transcranial resection of anterior midline skull base meningiomas. World Neurosurg 77:713724, 2012

    • Search Google Scholar
    • Export Citation
  • 8

    Komotar RJ, , Starke RM, , Raper DMS, , Anand VK, & Schwartz TH: Endoscopic versus transsphenoidal microscopic and transcranial resection of craniopharyngiomas. World Neurosurg 77:329341, 2012

    • Search Google Scholar
    • Export Citation
  • 9

    Koutourousiou M, , Fernandez-Miranda JC, , Wang EW, , Snyderman CH, & Gardner PA: Endoscopic endonasal surgery for olfactory groove meningiomas: outcomes and limitations in 50 patients. Neurosurg Focus 37:4 E8, 2014

    • Search Google Scholar
    • Export Citation
  • 10

    Ottenhausen M, , Banu M, , Placantonakis DG, , Tsiouris AJ, , Khan OH, , Anand VK, & Schwartz TH: Endoscopic endonasal resection of suprasellar meningiomas: the importance of case selection and experience in determining extent of resection, visual improvement and complications. World Neurosurg 83:442449, 2014

    • Search Google Scholar
    • Export Citation

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 615 381 4
PDF Downloads 144 47 2
EPUB Downloads 0 0 0