Despite the relatively benign behavior of ONSMs, surgical excision is often warranted to prevent extension, particularly when accompanied by disfiguring proptosis or severe ipsilateral visual loss. Unfortunately, the location of these lesions relative to the optic nerve often results in high visual impairment associated with surgical intervention, with over 90% of cases resulting in blindness following complete resection [11]. Controversies in the surgical management of ONSMs have existed over the last two decades [2]. In this paper, we describe a novel surgical technique and suggest some preoperative indications of ETA with ONT for patients who had the intention of total tumor resection. By highlighting our clinical experience utilizing this technique, we strive to demonstrate that this less invasive approach offers satisfactory access to the apex of the visual cone without resorting to conventional craniofacial approaches, which may be complicated by facial incisions and brain retraction, or lateral orbitotomy approach with OM, which may evoke disfigurement and mental distress. Ultimately, our study suggests that this microinvasive technique leads to noteworthy cosmetic outcomes and holds the potential for achieving radical cures of ONSMs.

Although the main treatment strategy concerning achieving the best vision enhancement outcome is essential to choose the most appropriate approach, safe and effective prevention of further tumor damage to the opposite eye or brain becomes a more important consideration when the patient experienced long-term vision loss and/or disfiguring proptosis. Peerooz Saeed et al. suggested that patients with a blind eye and significant proptosis were candidates for total excision [1]. According to the tumor location of 73 patients with ONSMs, Schick et al. classified ONSMs into different types and subtypes. Among those, nine patients with preoperative blindness underwent transection of the optic nerve [10]. In another study reported by them, 11 blind patients with painful disfiguring proptosis, whose ON was crossed [12]. In a series of 24 cases of ONSM, seven cases with blindness or light perception performed an ONT and none of them had either clinical or radiological recurrence [13]. In four of our 23 cases, they all recurred in orbit due to non-total resection of tumors. And whether underwent ETA or LOA, after GTR with transection of the ON, none of them recurred either (Figs. 2 and 3). To sum up, complete surgical resection with ONT is rarely warranted in the management of ONSM except in patients suffering from blindness or disfiguring proptosis. Transaction may also have a role if the tumors with the tendency of intracranial extension, to prevent chiasmatic spread to the contralateral ON [2, 14]. Therefore, it is virtually possible to extirpate these tumors and reduce the risk of recurrence. How to transect the optic nerve without compromising the surrounding normal neurovascular structures to complete tumor resection is an important problem. The endoscopic transnasal approach may be the best answer.

Significant advances in endoscopic transnasal (ETA) and microinvasive surgical approaches have revolutionized the intervention of orbital tumors. And ETA has a wide range of flexible modifications and coordinations available depending on the origin and extent of the targeted disease [15, 16]. In previous studies, endoscopic techniques were introduced to bony decompress the orbital tumors [17, 18] and dramatically improved the outcomes in skull base tumors surgery such as sellar [19,20,21], olfactory groove [22], and spheno-orbital meningiomas [23]. Nevertheless, the application of ETA in meningiomas involved in the optic nerve is rare. Four primary ONSMs cases were treated with EOND surgery with stable clinical results [24]. Endoscopic transnasal surgery was performed for one case of aggressive optic sheath meningioma. Partial removal of the tumor was achieved and visual symptoms of the patient were significantly improved [25]. Similarly, in another patient with long-lasting blindness, the fully endoscopic technique enabled surgeons to subtotal remove the lesion [26].

In our series, three cases with NLP, one case with LP, and 10 cases with residual vision underwent ETA and ONT joint surgery. According to the recommendations of treatment for different tumor types from Schick et al., all patients opted for surgery in compliance with the recommendations [10]. Based on previous research, only patients with bad visual acuity and disfiguring proptosis were subject to transection of the ON, but our data concerning the subset of patients who had vision greater than NLP or LP at presentation are included. For these patients, there are four main reasons for GTR with ONT: (1) patients and their families were more concerned about the mass than vision loss; (2) the mass increases and affects vision gradually; (3) there is a risk of intracranial metastasis; and (4) exophthalmos affect patients’ appearances. Visual loss after transection surgery is the norm, and reasonably, tumors with greater tightness with the optic nerve have less chance of attaining visual cure under micromanipulation. In the absence of a more ideal management algorithm, ETA performed in these patients is still an available and microinvasive option, especially in adults with unstable vision and disfiguring proptosis. On the other hand, ONT of symptomatic patients could preclude contralateral visual injury.

In our view, the risk of affection of the contralateral optic nerve and brain and a large volume of tumor are also indications of ONT, not just vision loss and/or disfiguring proptosis. Even though there are optimal approaches in a minimally invasive 360° circumferential access to target orbital tumors to avoid crossing the plane of the optic nerve [4, 5], as a tumor arising from the arachnoid of the intraorbital optic nerve, ONSM is difficult to be removed completely without damaging the optic nerve. The cavernous hemangioma exclusively endonasal resection (CHEER) staging system was developed in 2019 to facilitate research on endonasal resection of orbital cavernous hemangiomas [27]. And direct retraction of the optic nerve was avoided in this staging system. The more locations where tumors clearly involved, the higher stage was used. Because the inferomedial muscular trunk of the ophthalmic artery (IMT) is considered to be the next most important intraorbital structure following the ON [28], the orbital space posterior to the IMT (stage IV) is divided into a high-risk zone where the lesion lie within millimeters of the ON. A meta-analysis suggested that the CHEER staging system had a broader application to benign orbital tumors including meningioma [29]. Based on this staging system, there are 11 lesions anterior to the optic canal (stage IVA), four lesions extending through the optic canal (stage IVB), and one lesion extending into the intracranial location (stage VA) of our 16 cases in ETA group. Taking the opinions of multidisciplinary panelists in orbital tumor surgery into account, the expectation of complete excision by endonasal resection declined with higher stages (stages IV and V) while the anticipated risks for vision loss increased [27]. Therefore, it was very difficult for our patients to remove the tumor without ONT. Even though the Simpson Grade may be antiquated and hard to predict recurrence-free survival for meningiomas according to recent studies [30,31,32,33,34], the goal of surgery should also be the maximal safe resection of the tumor. And combined with ONT, GTR can be obtained more safely and efficiently.

By follow-up via telephone, all patients who received ONT said they preferred complete resection of the tumor knowing they had a tumor and would lose vision. And for them, a minimally invasive approach that preserves the eyeball was better. Case 18 clearly stated that she became unconfident and self-abasement due to changes in her appearance after the OM. Although most patients undergoing OM were lost to follow-up due to age or the long length of the operation, the psychological problems of patient postoperation could not be neglected. Increasing attention is diverted to studying dimensions of preoperative and postoperative quality of life (QOL) of patients. In this regard, however, there have been so many methodological investigations of the improvement of vision of patients with ONSMs, omitting a psychopathological snake in the grass.

In comparison to intracranial tumors [35,36,37], none of foray has been made to quantify mental health for patients with tumors involved in the optic nerve because of low incidence, slow progression, and good prognosis. Our experience suggests that ONT is not only a favorable result for blind patients, but also an early intervention, a less mental burden, and a certain predictability for an individual with/without fair or good visual performance who is faced with an upcoming blindness and larger tumor mass. Therefore, it is unnecessary to just wait until the patients’ conditions meet the traditional indication to have an ONT. Although many treatment options can preserve the integrity of the optic nerve and improve vision, the associated risks of complications and recurrence should not be ignored [38]. A meningioma-specific quality-of-life questionnaire was designed specifically for evaluating QOL in meningioma patients [39]. And we tried to perform interviews via telephone with patients to better understand and capture health-related QOL in the ONSM population. Unfortunately, due to the low education level of the patients and the fact that more than half of the patients were over 50 years old, it was difficult to communicate accurately and fully assess their postoperative QOL. Also, it was unfortunate that patient-reported QOL in endoscopically managed orbital meningioma has never been well elucidated, nor has the surgical effect on QOL been ascertained as evidence is limited to small cohorts. We hope that with larger, multicenter collaborative studies in the future, the role of endoscopic transnasal approaches for QOL in ONSM management will become clearer. Thus, there can be more evidence to break the rules and broaden the applicability of ONT.

In the LOA group, poor eyesight of patients led to the justifiability of ONT. Unfortunately, the only downside was the removal of the eyeball, which could diminish patients’ quality of life due to the lack of natural appearance and limited movement of artificial eyeballs. Though no professional questionnaire was used to evaluate this conclusion, OM during surgery should be avoided. Compared to the two groups of clinical outcomes, without removal of the eyeball and skin incision, ETA provides a shorter and more direct operative corridor to total remove the lesions located in the orbit and optic canal via the transethmoidal-sphenoidal incision. This access-related advantage is clinically associated with excellent cosmesis, reduced postoperative pain, and wound infection. Although ETA with a risk of neurological complications, the defects cannot obscure the virtues. Statistically, the hospitalization time for patients who underwent tumor resection via the ETAs or lateral orbitotomy method both showed a short length of hospitalization (P > 0.05). However, LOA obtained GTR by OM, which resulted in poor cosmetic results. The simple LOA method, while preserving the eyeball, can also leave surgical incision scars on the face, thereby affecting aesthetics. It is therefore evident that ETA serves as a microinvasive approach that is associated with excellent cosmetic outcomes and may be better suited for patients seeking a minimally invasive procedure. However, all the LOA selected in this study were performed before 2017. Advancements in contemporary techniques suggest that such drastic measures may not be universally required, and preservation of the eye and orbit can be achieved. Additionally, all the ETA procedures selected in this study were performed after 2016. It is noteworthy that potential bias was introduced when comparing LOA to ETA. This study needs further refinement of the techniques for both surgical methods in the future. While ensuring the preservation of the eyeball in both approaches, it is essential to clarify the differences in patient cosmetic outcomes resulting from these two surgical methods. Moreover, there is a learning curve for surgeons to proficiently perform ETA. Also, during ETA, particular emphasis should be placed on safeguarding the extraocular muscles while approaching the optic nerve mass. Extraocular muscle injury or vascular bleeding can occur easily, especially in inexperienced hands. Therefore, patient preference and the surgeon’s extensive surgical experience are particularly crucial for selecting such procedures.