Discussion

Over the past decades, several open approaches have been described for exposing the midline cranial base. ^{Reference De Divitiis, Esposito, Cappabianca, Cavallo and de Divitiis12–Reference Raco, Bristot, Domenicucci and Cantore15} While transcranial procedures provide adequate exposure and generally good outcomes, they also have limitations ^{Reference Plou, Serioli and Leonel16} .

Endoscope-assisted surgery offers visualization that is comparable to or even superior to that of microsurgery. ^{Reference Kassam, Carrau, Snyderman, Gardner and Mintz5,Reference Plou, Serioli and Leonel16,Reference Kassam, Snyderman, Mintz, Gardner and Carrau17} The high-resolution imaging of anatomical and pathological details during surgical resection allows surgeons to visualize and remove structures in difficult-to-access areas. This is particularly relevant in anterior skull base meningiomas, where conventional open approaches may pose significant challenges, including brain retraction, neurovascular manipulation, sinus obliteration, wound healing complications and cosmetic concerns. ^{Reference Plou, Serioli and Leonel16,Reference Borghei-Razavi, Eguiluz-Melendez and Wenping18}

Our series demonstrates that endoscopic approaches for the resection of these formidable lesions are not only safe but also effective, achieving high rates of total resection across lesions of varying locations and sizes, with no major associated complications. However, careful patient selection is crucial to minimizing the incidence of residual tumors by understanding the limitations of the endonasal corridor. ^{Reference Schroeder19}

Given their slow growth pattern and subfrontal location, OG meningiomas present insidiously and frequently achieve large size before detection. ^{Reference Hentschel and DeMonte20,Reference Jang, Jung, Jung, Moon and Kim21} A panoramic view of the ventral skull base can be obtained through a transcribriform corridor, allowing for the resection of these lesions with early tumor devascularization and, when feasible, removal of the dural attachment and involved hyperostotic bone. ^{Reference Zoli, Guaraldi, Pasquini, Frank and Mazzatenta6,Reference Dehdashti, Ganna, Witterick and Gentili10,Reference Plou, Serioli and Leonel16}

In our cohort, tumors in this location were larger in volume, commonly presented with symptoms such as headaches and olfactory changes, and were resected in a total or near-total fashion in 87.5% of cases. Residual tumors were primarily associated with larger tumor size and cases involving vascular encasement or invasion.

Previous studies have reported similar resection rates, identifying larger tumor size, calcification, close neurovascular relationships and brain invasion as limiting factors for complete resection. ^{Reference Koutourousiou, Fernandez-Miranda, Wang, Snyderman and Gardner22} No patients in the OG cohort experienced CSF leaks during the postoperative period. In tumors located in this region, lower CSF pressure and the descent of the frontal lobe into the surgical defect, combined with proper skull base reconstruction, help reduce the risk of leakage. ^{Reference Eloy, Shukla, Choudhry, Singh and Liu23}

Planum and TS meningiomas frequently present with visual dysfunction, ^{Reference Raco, Bristot, Domenicucci and Cantore15} as observed in our cohort, even in cases with small tumor sizes. The close relationship between these lesions and critical structures such as the prechiasmatic and chiasmatic segments of the optic nerves, arterial perforators and the pituitary stalk increases the challenge of achieving a safe and complete GTR in this region. Numerous large case series describing transcranial approaches to TS meningiomas have demonstrated the safety and efficacy of this widely used technique. ^{Reference Liu, Christiano, Patel, Tubbs and Eloy13,Reference Bowers, Altay and Couldwell14,Reference Plou, Serioli and Leonel16} However, despite advances in modern microsurgical techniques, the reported incidence of postoperative visual decline remains between 10 and 15%. ^{Reference Schick24} An endoscopic transplanum/transtuberculum approach, which avoids brain and optic apparatus retraction, is an appealing alternative to reduce the risk of visual dysfunction. The reported GTR rate for TS meningiomas in the literature ranges from 60 to 100%. ^{Reference Liu, Christiano, Patel, Tubbs and Eloy13,Reference Schick24,Reference Mahmoud, Nader and Al-Mefty25} However, it is difficult to compare the surgical outcomes between different studies directly due to the lack of uniform criteria. ^{Reference Sankhla, Jayashankar, Khan and Khan26}

In our cohort, we did not encounter any case of visual deterioration in the intra or post operative period; additionally, total or near-total resection was achieved in 82.4% of cases, while subtotal resections were primarily due to residual enhancing dura at the lateral margins of the cavity or tumor remnants closely related to the pituitary stalk/hypothalamic junction. In patients with preserved hormonal function, extensive manipulation of this region was avoided to minimize the risk of procedure-related morbidity.

In line with recent publications, multiple tumor characteristics, such as tumor size, optic canal involvement, vascular encasement, intracranial extension, surgery and radiation history, have an impact on the GTR rate of TSM. ^{Reference Jallo and Benjamin27,Reference Magill, Morshed and Lucas28} We believe that EEA surgery is a preferable option for smaller lesions with midline distribution as the extent of the lesion’s lateral extension is a key factor in determining the suitability of this approach. Our only case of recurrence occurred in the lateral region of the optic canal, an area that is not accessible via the endonasal endoscopic route. Moreover, while vascular encasement is not an absolute contraindication, it should be carefully considered when selecting the surgical approach. We encountered an arterial injury involving a posterior communicating artery branch encased by the tumor, though fortunately, no postoperative ischemic events were observed. The vascular relationship with the tumor was evident preoperatively. In our experience, vascular encasement is not an absolute contraindication. Tumor extension, along with familiarity with microdissection instruments, refined techniques, and surgical expertise, can enable safe resection even under these conditions.

Despite the unique advantages of EEAs, challenges remain, including the risk of complications such as CSF leaks. ^{Reference Laufer, Anand and Schwartz29} In our cohort, 16% of patients developed this complication, all of whom were in the TS group. This is likely due to the extensive arachnoid dissection required for these lesions. Notably, these events were documented during the early years of our cohort, with no recent cases of CSF leaks in our most recent cases in which multilayered reconstruction techniques were adopted. All of these cases were successfully managed with lumbar drainage, and no reintervention was required.

Limitations of our study include its retrospective nature and the inherent biases associated with such studies. Finally, reconstruction techniques and case complexity evolved over the course of the study, introducing a variable that cannot be accurately measured and may have impacted the overall results.