Letter to the Editor: Resection of olfactory groove meningiomas

Ankit Bansal MCh and Sumit Sinha MCh
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  • All India Institute of Medical Sciences, New Delhi, India
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TO THE EDITOR: We congratulate Banu et al.1 on their article comparing 2 minimally invasive approaches for dealing with olfactory groove meningiomas (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 authors concluded, “the supraorbital eyebrow approach, with endoscopic assistance, leads to a higher extent of resection and lower rate of complications than the purely endonasal endoscopic approach.”

The study, however, has some inherent methodological shortcomings to which we would like to draw the authors' attention. The mean tumor volume was 19.6 cm3 in the endonasal group, 33.5 cm3 in the supraorbital group, and 37.8 cm3 in the combined group. It is not methodologically appropriate to compare 2 techniques in patients with different tumor volumes. Moreover, the derived conclusions may be an overestimate, as the number of cases in each group is small: purely endonasal (6 cases), supraorbital eyebrow (microscopic with endoscopic assistance, 7 cases), and combined endonasal endoscopic with either the bicoronal or eyebrow microscopic approach (6 cases). The conclusions regarding the superiority of any one approach cannot be deduced from a series based on such a small number of patients. The authors have not mentioned when postoperative MRI was performed, within 48 hours of surgery or later, to determine whether there was residual or recurrent tumor.

The reported infection rate of 15% with use of the endoscope is quite alarming in this era of advanced endoscopic techniques. In various series reported in the literature, the incidence of meningitis in patients undergoing endoscopic supraorbital approaches and endoscopic skull base surgery ranges from 1.03% to 1.8%.2,3

The numbers in Table 3 do not tally.

It is unclear why the patients in Case 14 (tumor volume 3.24 cm3) and Case 19 (tumor volume 14.78 cm3) were treated by means of a combined approach. Tumors of that size or larger may be operated on via either an endonasal or an eyebrow approach alone, thereby reducing the morbidity of the combined procedure.

References

  • 1

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

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  • 2

    Gazzeri R, , Nishiyama Y, & Teo C: Endoscopic supraorbital eyebrow approach for surgical treatment of extraaxial and intraxial tumors. Neurosurg Focus 37:4 E20, 2014

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  • 3

    Kono Y, , Prevedello DM, , Snyderman CH, , Gardner PA, , Kassam AB, & Carrau RL, et al.: One thousand endoscopic skull base surgical procedures demystifying the infection potential: incidence and description of postoperative meningitis and brain abscesses. Infect Control Hosp Epidemiol 32:7783, 2011

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Disclosures

The authors report no conflict of interest.

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  • Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, NY

Response

We thank the authors for their thoughtful comments on our article. They make several points, and we will respond to them individually. The first comment is that the number of cases in this series is small and the size of the tumors removed endonasally was smaller than those removed through an eyebrow incision or through a combined approach. With regard to the first point, olfactory groove meningiomas are relatively uncommon tumors, and most single-center series are relatively small. However, even with this small number of patients we found a statistically significant result, which means that the finding is robust. A negative result should be suspect with such a small series. As for the size of the tumor, there is clearly a selection bias, and we chose smaller tumors for the endonasal approach since those tumors did not extend laterally past the lamina papyracea and were suitable for this approach. This inherent bias would have favored better results in the endonasal endoscopic group; however, we found just the opposite, namely worse results in this group.

The authors also note that we failed to mention the timing of the postoperative scans. This was clearly an oversight in our paper. We generally obtain postoperative scans within 48 hours after surgery and use these scans to determine the extent of resection. Moreover, we know of no evidence—and the authors do not provide any—indicating that the timing of the postoperative scan (48 hours after surgery or later) makes a difference in estimating the extent of resection for meningioma surgery. Thus, our oversight in not reporting the timing of the scan should have no bearing on the reliability of the results.

Finally, the authors feel that the 15% infection rate we report in our small endonasal series is too high compared with the rates reported in the literature and reference a paper on 1000 endonasal endoscopic surgeries performed at the University of Pittsburgh that found an infection rate of 1.8%.1 The majority of the surgeries in that paper, however, were pituitary adenomas, which are known to be associated with a much lower rate of meningitis and other infections than more complex cases like meningiomas. In fact, in that very same article, the complexity of the case was a risk factor for infection, and according to my calculation, their infection rate with more complex cases was actually 5%. Moreover, when this same group reported their complication rate in a series of 50 olfactory groove meningiomas removed through an endonasal endoscopic approach, their infection rate was 8% for meningitis and intracranial abscess with an additional 10% of patients having a sinus infection.2 Hence, our 1 case of infection, which resulted in a 15% infection rate, is probably not far from the rates at other centers. More importantly, the overall complication rate for endonasal olfactory groove meningioma surgery in our series was 83%. While this may appear high, in a series of 50 olfactory groove meningiomas removed by the University of Pittsburgh group, these authors report that 70% of their patients required 2 surgeries, there was a complication rate of approximately 90%, the anosmia rate was 100%, and the average length of stay was 11 days.2,3

Given these suboptimal results of endonasal surgery for olfactory groove meningiomas, we propose the supraorbital eyebrow incision with endoscopic assistance as a more suitable minimally invasive alternative that provides the benefits of minimizing brain retraction, preservation of the sagittal sinus with the possibility of preserving olfaction, and the potential for equally high rates of gross-total resection. In our opinion, the endonasal endoscopic approach can be offered to patients with olfactory groove meningiomas as an additional minimally invasive approach for those tumors that invade into the sinuses or through the cribriform plate.

References

  • 1

    Kono Y, , Prevedello DM, , Snyderman CH, , Gardner PA, , Kassam AB, & Carrau RL, et al.: One thousand endoscopic skull base surgical procedures demystifying the infection potential: incidence and description of postoperative meningitis and brain abscesses. Infect Control Hosp Epidemiol 32:7783, 2011

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    • Export Citation
  • 2

    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

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  • 3

    Schwartz TH: Editorial. Should endoscopic endonasal surgery be used in the treatment of olfactory groove meningiomas?. Neurosurg Focus 37:4 E9, 2014

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  • 1

    Banu MA, , Mehta A, , Ottenhausen M, , Fraser JF, , Patel KS, & Szentirmai O, et al.: 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
  • 2

    Gazzeri R, , Nishiyama Y, & Teo C: Endoscopic supraorbital eyebrow approach for surgical treatment of extraaxial and intraxial tumors. Neurosurg Focus 37:4 E20, 2014

    • Search Google Scholar
    • Export Citation
  • 3

    Kono Y, , Prevedello DM, , Snyderman CH, , Gardner PA, , Kassam AB, & Carrau RL, et al.: One thousand endoscopic skull base surgical procedures demystifying the infection potential: incidence and description of postoperative meningitis and brain abscesses. Infect Control Hosp Epidemiol 32:7783, 2011

    • Search Google Scholar
    • Export Citation
  • 1

    Kono Y, , Prevedello DM, , Snyderman CH, , Gardner PA, , Kassam AB, & Carrau RL, et al.: One thousand endoscopic skull base surgical procedures demystifying the infection potential: incidence and description of postoperative meningitis and brain abscesses. Infect Control Hosp Epidemiol 32:7783, 2011

    • Search Google Scholar
    • Export Citation
  • 2

    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
  • 3

    Schwartz TH: Editorial. Should endoscopic endonasal surgery be used in the treatment of olfactory groove meningiomas?. Neurosurg Focus 37:4 E9, 2014

    • Search Google Scholar
    • Export Citation

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