Surgical Freedom Evaluation During Optic Nerve Decompression: Laboratory Investigation

Spheno-Orbital Meningiomas: The Rationale behind the Decision-Making Process of Treatment Strategy

Surgery stands as the primary treatment for spheno-orbital meningiomas, following a symptoms-oriented approach. We discussed the decision-making process behind surgical strategies through a review of medical records from 80 patients who underwent surgical resection at the University of Naples Federico II. Different surgical approaches were employed based on the tumor's location relative to the optic nerve's long axis, categorized into lateral (type I), medial (type II), and diffuse (type III). We examined clinical, neuroradiological, surgical, pathological, and outcome factors. Proptosis emerged as the most frequent symptom (97%), followed by visual impairment (59%) and ocular motility issues (35%). Type I represented 20%, type II 43%, and type III 17%. Growth primarily affected the optic canal (74%), superior orbital fissure (65%), anterior clinoid (60%), and orbital apex (59%). The resection outcomes varied, with Simpson grades I and II achieved in all type I cases, 67.5% of type II, and 18% of type III. Recurrence rates were highest in type II (41.8%) and type III (59%). Improvement was notable in proptosis (68%) and visual function (51%, predominantly type I). Surgery for spheno-orbital meningiomas should be tailored to each patient, considering individual characteristics and tumor features to improve quality of life by addressing primary symptoms like proptosis and visual deficits.

Neurosurgery for the rhinologist

PURPOSE OF REVIEW

The purpose of this review is to provide a comprehensive anatomical appraisal of the neurosurgical anatomy exposed through the endonasal and paranasal sinuses routes, focusing on the most common expanded endonasal approaches (EEAs) as well as recent advances in this surgical field.

RECENT FINDINGS

The EEAs are redefining the management of skull base pathology. Neurovascular structures previously considered a limitation, can be now approached through these surgical corridors. Advances in this field include the development of new surgical techniques and routes that allow better visualization and access to pathologies located in the ventral skull base. Understanding the surgical anatomy related to EEAs is essential not only for neurosurgeons but also for rhinologists.

SUMMARY

Knowledge of the surgical anatomy of the most common EEAs that utilize paranasal sinuses as a surgical corridor enables more effective management of complex skull base pathologies. Comprehensive anatomical knowledge of these corridors and the surrounding neurovascular structures is crucial to maximize benefits of EEAs and improve outcomes.

[Optic canal stenosis in Crouzon syndrome: a case report and literature review]

BACKGROUND

Incidence of Crouzon syndrome is 1 per 25.000-31.000 newborns. This syndrome is extremely rarely accompanied by optic canal stenosis.

OBJECTIVE

To present a patient with Crouzon syndrome and optic canal stenosis, to discuss the management of such patients considering own and literature data.

MATERIAL AND METHODS

A 6-year-old boy presented with Crouzon syndrome (verified by molecular genetic research, i.e. FGFR2 gene mutation). The patient underwent 3 surgeries for craniosynostosis and hydrocephalus. Nevertheless, visual acuity progressively decreased despite patent ventriculoperitoneal shunt. Examination revealed severe decrease in visual functions with optic disc congestion under secondary atrophy. MRI data on subarachnoid CSF accumulation over both optic nerves potentially indicated optic canal stenosis. This assumption was confirmed by 3D CT.

RESULTS

The patient underwent decompression of both optic canals with subsequent improvement of visual functions.

CONCLUSION

Vision decrease following Crouzon syndrome may be due to optic canal stenosis. Decompression may be effective, even in long-term course of disease, and improve visual functions.

Surgical Anatomy of the Microscopic and Endoscopic Transorbital Approach to the Middle Fossa and Cavernous Sinus: Anatomo-Radiological Study with Clinical Applications

BACKGROUND

The transorbital approaches (TOAs) have acquired growing notoriety, thanks to their ability to offer alternative corridors to the skull base. However, the limited access and the unfamiliarity with this surgical perspective make recognition of key landmarks difficult, especially for less experienced surgeons. The study wants to offer a detailed description of the anatomy to comprehend the potential and limitations of TOAs.

METHODS

Measurements of the orbit region and the surrounding areas were performed on two hundred high-resolution CT scans and thirty-nine dry skulls. Five specimens were dissected to illustrate the TOA, and one was used to perform the extradural clinoidectomy. Three clinical cases highlighted the surgical applications.

RESULTS

A step-by-step description of the key steps of the TOA was proposed and a comparison with the transcranial anterior clinoidectomy was discussed. The mean work distance was 6.1 ± 0.4 cm, and the lateral working angle increased 20 ± 5.4° after removing the lateral orbital rim.

CONCLUSIONS

TOAs are indicated in selected cases when tumor involves the lateral portion of the cavernous sinus or the middle skull base, obtaining a direct decompression of the optic nerve and avoiding excessive manipulation of the neurovascular structures. Comprehension of surgical anatomy of the orbit and its surrounding structures is essential to safely perform these approaches.

Management of the skull base invasion in spheno-orbital meningiomas

BACKGROUND

The tumor invasion of the skull base structures is very frequent in spheno-orbital meningiomas. The aim of the present study is to evaluate the invasion rate of skull base structures and the best surgical approach and management.

METHODS

The surgical series of 80 spheno-orbital meningiomas was reviewed. The tumors were classified according to the intraorbital location with respect to the optic nerve axes into three types: I-lateral: II-medial; III-diffuse. The invasion of the orbital apex, optic canal, superior orbital fissure, anterior clinoid, ethmoid-sphenoid sinuses, and infratemporal fossa was evaluated. The rate and extension of involvement of these structures was correlated with the intraorbital location and the surgical approach. The preoperative ophtalmological symptoms and signs and their outcome were also evaluated.

RESULTS

Proptosis was found in 79 patients (97%), variable decrease of the visual function in 47 patients (59%), and deficits of the eye movements in 28(35%). The invasion of the optic canal (74%), superior orbital fissure (65%), anterior clinoid (60%), and orbital apex (59%) was more frequently found, whereas the tumor extension into the ethmoid-sphenoid sinuses (4%) and infratemporal fossa (4%) was rare. Types II and III meningiomas showed significantly higher involvement of the skull base structures than type I ones, which only had 15% invasion of the optic canal. Remission or significant improvement of the visual function occurred postoperatively in 24 among 47 cases (51%), with a higher rate for type I meningiomas vs. other types (p = 0.021, p = 0.019) and worsening in 7 (15%).

CONCLUSIONS

Spheno-orbital meningiomas growing in the lateral orbital compartment show no involvement of the skull base structures excepting the optic canal as compared to those growing medially or diffusely. The surgical resection of tumor invading the skull base structures should be more extensive as possible, but the risk of optic and oculomotor deficits must be avoided.

Endoscopic Optic Nerve Decompression for Direct Traumatic Optic Neuropathy : Our 10 Years Experience

Traumatic optic neuropathy (TON) can be classified into direct or indirect types. Direct optic injury usually results from optic nerve avulsion ,laceration or compression by fracture, fracture segment impingement or a resultant hematoma. Indirect optic injury is caused by increased intracanalicular pressure resulting in ischemia and disruption of neurofeedback channels. The prognosis of TON is usually quite poor. To date, no standardized treatment protocol has been developed for TON. In this study we are assessing the visual improvement in patients with direct TON who underwent endoscopic optic nerve decompression in the last 10 years. A retrospective study of 32 cases of optic nerve decompression for direct TON in the last 10 years. Preoperative and postoperative visual assessment were done and followed up for 3 months. There was complete improvement in vision in 17% of patients when optic nerve decompression was done within 72 h of trauma; whereas 31% cases had only partial improvement when done between 3 and 7 days. And there was no improvement when done after 7 days. Endoscopic optic nerve decompression is a minimally invasive surgery for direct traumatic optic neuropathy; with minimal or no complications when done by an experienced ENT surgeon. Other important prognostic factors include timing of surgery and preoperative visual status.

Alternative Path for Optic Nerve Decompression in Pseudotumor Cerebri With Full Endoscopic Lateral Transorbital Approach

Endonasal endoscopic approaches are the most preferred surgical methods in patients with pseudotumor cerebri because of easy access to the optic nerve, but the choice of this technique may not apply to all endoscopic endonasal cases. Moreover, there may be difficulties in practice in some cases, including the coronavirus disease 2019 pandemic. This study aimed to suggest an alternative endoscopic approach by lateral orbitotomy for optic nerve decompression in patients with pseudotumor cerebri. The study was performed using 5 fresh-frozen cadaver heads (bilaterally, total of 10 sides) injected intravenously with colored silicone preserved in the cold chain. An average of 2.5 cm skin incision was made to fit the lateral orbitotomy. The lengths of the recurrent meningeal artery (mm), the meningo-orbital band (mm), and the optic nerve (mm) to the orbital margin were measured. After these morphometric measurements, optic nerve decompression was performed endoscopically, and the length of the decompression was measured (mm). The average length (mm) between the orbital rim and meningeal recurrent artery (or meningolacrimal branch) was 16.2 mm, between the orbital rim and the meningo-orbital band was 18.5 mm, and between the orbital rim and optic nerve was 44.1 mm. The average optic nerve decompression length was 4.4 mm. The endoscopic lateral orbitotomy approach provides easy access to the optic nerve by anatomically following the recurrent meningeal artery and the meningo-orbital band. It can be a safe second-line approach after endonasal approaches for optic nerve decompression in pseudotumor cerebri.

Extended endoscopic transorbital approach with superior-lateral orbital rim osteotomy: cadaveric feasibility study and clinical implications (SevEN-007)

OBJECTIVE

The endoscopic transorbital approach (ETOA) has been developed, permitting a new surgical corridor. Due to the vertical limitation of the ETOA, some lesions of the anterior cranial fossa are difficult to access. The ETOA with superior-lateral orbital rim (SLOR) osteotomy can achieve surgical freedom of vertical as well as horizontal movement. The purpose of this study was to confirm the feasibility of the ETOA with SLOR osteotomy.

METHODS

Anatomical dissections were performed in 5 cadaveric heads with a neuroendoscope and neuronavigation system. ETOA with SLOR osteotomy was performed on one side of the head, and ETOA with lateral orbital rim (LOR) osteotomy was performed on the other side. After analysis of the results of the cadaveric study, the ETOA with SLOR osteotomy was applied in 6 clinical cases.

RESULTS

The horizontal and vertical movement range through ETOA with SLOR osteotomy (43.8° ± 7.49° and 36.1° ± 3.32°, respectively) was improved over ETOA with LOR osteotomy (31.8° ± 5.49° and 23.3° ± 1.34°, respectively) (p < 0.01). Surgical freedom through ETOA with SLOR osteotomy (6025.1 ± 220.1 mm3) was increased relative to ETOA with LOR osteotomy (4191.3 ± 57.2 mm3) (p < 0.01); these values are expressed as the mean ± SD. Access levels of ETOA with SLOR osteotomy were comfortable, including anterior skull base lesion and superior orbital area. The view range of the endoscope for anterior skull base lesions was increased through ETOA with SLOR osteotomy. After SLOR osteotomy, the space for moving surgical instruments and the endoscope was widened. Anterior clinoidectomy could be achieved successfully using ETOA with SLOR osteotomy. The authors performed ETOA with SLOR osteotomy in 6 cases of brain tumor. In all 6 cases, complete removal of the tumor was successfully accomplished. In the 3 cases of anterior clinoidal meningioma, anterior clinoidectomy was performed easily and safely, and manipulation of the extended dural margin and origin dura mater was possible. There was no complication related to this approach.

CONCLUSIONS

The authors evaluated the clinical feasibility of ETOA with SLOR osteotomy based on a cadaveric study. ETOA with SLOR osteotomy could be applied to more diverse disease groups that do not permit conventional ETOA or to cases in which surgical application is challenging. ETOA with SLOR osteotomy might serve as an opportunity to broaden the indication for the ETOA.

Endoscopic Endonasal versus Transcranial Optic Canal Decompression: A Morphometric, Cadaveric Study

Introduction Decompression of the optic nerve within the optic canal is indicated for compressive visual decline. The two most common approaches utilized for optic canal decompression are a medial approach with an endoscopic endonasal approach and a lateral approach with a craniotomy. Our study is a cadaveric anatomical study comparing the length and circumference of the orbit decompressed via an endoscopic endonasal approach versus a frontotemporal craniotomy.

Methods Five cadaveric specimens were utilized. Predissection computed tomography (CT) scans were performed on each specimen. On each specimen, a standard frontotemporal craniotomy with anterior clinoidectomy and superolateral orbital decompression was performed on one side and an endoscopic endonasal approach with medial wall decompression was performed on the contralateral side. Post-dissection CT scans were performed. An independent radiologist provided measurements of the length (mm) and circumference (degrees) of optic canal decompression bilaterally.

Results The mean length of optic canal decompression for open and endoscopic approach was 13 mm (range 12–15 mm) and 12.4 mm (range 10–16 mm), respectively. The mean circumference of decompression for open and endoscopic approaches was 252.8 degrees (range 205–280 degrees) and 124.6 degrees (range 100–163 degrees), respectively.

Conclusion The endoscopic endonasal and the transcranial approaches provide a similar length of optic canal decompression, but the transcranial approach leads to greater circumferential decompression. The endoscopic endonasal approach has the benefit of being minimally invasive, though. Ultimately, the surgical approach decision should be based on the location of the pathology and the surgeon's comfort.

Predictors for Surgeries With the Endoscope-Navigation System for Traumatic Optic Neuropathy and its Clinical Assessment

BACKGROUND

To assess surgeries with the endoscope-navigation system (ENS) in patients who underwent traumatic optic neuropathy (TON) and find predictors for best corrected visual acuity (BCVA) outcomes.

METHODS

The clinical data of 96 consecutive TON patients (96 eyes) who underwent decompression surgery with ENS in the Department of Ophthalmology, Shanghai Ninth People's Hospital, from January 2013 to December 2019 were retrospectively reviewed and analyzed. A binary logistic regression was performed to establish a predictive model for BCVA after treatment as TON outcome.

RESULTS

By practicing ENS, 49/96 (51.0%) TON patients got improvement in BCVA, whereas the improvement rate of patients with BCVA of light perception or better was 72.5% (29/40). Hemorrhage within the postethmoid and/or sphenoid sinus, orbital fracture, time interval between trauma and treatment, and BCVA before treatment were predictors for BCVA improvement in TON patients by practicing ENS surgery. The area under raw current curves of the predictive model was 0.826.

CONCLUSIONS

Surgeries with the ENS showed positive outcomes for TON patients, especially for those with better BCVA before treatment, shorter time interval between trauma and treatment, without orbital fracture or hemorrhage within the postethmoid and/or sphenoid sinus.

Optimization of orbital retraction during endoscopic transorbital approach via quantitative measurement of the intraocular pressure - [SevEN 006]

Background

Increased use of the transorbital approach (TOA) warrants greater understanding of the risk of increased intraocular pressure (IOP) and intraorbital pressure (IORP) due to orbital compression. We aimed to investigate the changes in IOP and IORP in response to orbital retraction in TOA and establish a method for the continuous measurement of intraoperative IORP.

Methods

We assessed nine patients who underwent TOA surgery from January 2017 to December 2019, in addition to five cadavers. IORP and IOP were measured using a cannula needle monitor, tonometer, cuff manometer, and micro strain gauge monitor.

Results

In all nine clinical cases and five cadavers, increased physical compression of the orbit increased the IOP and IORP in a curvilinear pattern. In clinical cases, when the orbit was compressed 1.5 cm from the lateral margin in the sagittal plane, the mean IOP and IORP were 25.4 ± 5.2 mmHg and 14 ± 9.2 mmH₂O, respectively. The IORP satisfactorily reflected the IOP (Pearson correlation coefficient = 0.824, p < 0.001).

Conclusion

We measured IOP and IORP simultaneously during orbital compression to gain basic information on pressure changes. In clinical cases, the change in the IOP could be conveniently and noninvasively monitored using continuous IORP measurements.

The Role of the Transorbital Superior Eyelid Approach in the Management of Selected Spheno-orbital Meningiomas: In-Depth Analysis of Indications, Technique, and Outcomes from the Study of a Cohort of 35 Patients

Objective Primary goal in spheno-orbital meningioma (SOM) surgery still remains complete resection. Nevertheless, given their highly infiltrative nature, a growing body of literature suggests to shift toward function-sparing surgeries. We here present our experience in the management of SOMs through the endoscopic superior eyelid approach (SEA).

Methods Surgical database from our multidisciplinary work group was retrospectively reviewed to identify patients treated for SOMs in the last 10 years by our senior authors, analyzing and correlating clinical, radiological, and outcome variables among the different approaches used.

Results There were 35 patients (mean age of 57.3 ± 12.86 years), with a mean follow-up of 31.5 months (range: 6–84 months). The most common preoperative complaint was proptosis (62.9%) followed by diplopia and visual deficit. Greater and lesser sphenoid wings were the areas mainly involved by the pathology (91.4% and 88.6%, respectively), whereas orbital invasion was evidenced in one-third of cases. Patients were operated on through craniotomic (48.6%), endoscopic superior eyelid (37.1%), and combined cranioendoscopic (14.3%) approaches. Simpson grades 0 to II were accomplished in 46.2% of SEA and 76.5% of craniotomies. All patients with a preoperative visual deficit improved in the postoperative period, independently from the approach used. On patients who underwent endoscopic SEA, there was improved their short-/long-term postoperative Karnofsky Performance Status.

Conclusions Endoscopic SEA is a safe and effective alternative to transcranial approaches in very selected cases of SOMs, where the planned primary objective was to obtain a maximally safe resection, aimed at symptom relief, rather than a gross total resection at any cost.

[Transcranial microsurgical decompression of the optic canal in surgical treatment of meningiomas of the sellar region]

RATIONALE

When removing the meningiomas of the sellar region, there is always a risk of visual impairment for various reasons, in particular, as a result of traction damage to the optic nerve. Decompression of the optic canal increases nerve mobility during tumor manipulation. In cases of meningioma growing into the canal, its decompression often seems necessary.

AIM

Evaluation of the effectiveness and risks of performing decompression of the optic canal.

MATERIALS AND METHODS

The study included patients with meningiomas of the parasellar location, who underwent surgical treatment at the Burdenko Neurosurgical Center for the period from 2001 to 2017. They were divided into two groups - main and control. The main group consisted of 129 patients who underwent decompression of the optic nerve canals when the tumor was removed. The tumor matrix in this group was most often located in the region of the tuberum sellae, supradiaphragmally, in the region of the anterior clinoid process and the optic canal. In 31 cases, decompression was bilateral - during one operation and using one access in 27 patients; in 4 cases, the decompression of the second canal was delayed for 1.5-3 months after the first operation. 160 decompressions were performed by the intradural and 7 - by extradural methods. During intradural decompression, the roof of the optic canal was resected, and during extradural decompression, the lateral wall of the canal was trephined. The control group consisted of 308 patients who did not undergo canal decompression when the tumor was removed. It included meningiomas with a predominant location of the matrix in the area of the tuberclum and diaphragm of the sella. Tumors in both groups were removed according to the same principles (matrix coagulation, mainly the gradual removal of the tumor, the use of ultrasonic aspirator, a situational decision on the radicality of the operation, etc.). The main difference between operations in these two groups was only canal related algorithms (with or without its trepanation), as well as the probable prevalence of significant lateral tumor growth in cases with canal trepanation. Visual functions in the «primary» group were evaluated before and after operations with trepanation of the canal depending on various factors - the initial state of vision and the radicality of the tumor excision, including removal from the canal. The differences in the postoperative dynamics of vision in the main and control groups were studied. The primary data processing was carried out using the program MSExcel. Secondary statistical processing was carried out using the program Statistica. To assess the statistical significance of differences in the results obtained in the compared patient groups, the Chi-square test was used, and in the case of small groups - the exact Fisher test was applied.

RESULTS

In the main group postoperative vision improvement of varying degrees on the side of trepanation was registered in 36.9% (59 out of 160) cases, no vision changes were found in 36.9% (59 out of 160), and in 26,2% (42 out of 160) the eyesight deteriorated. If preserving vision is attributed to a satisfactory result, then in general the results of these operations should be considered good. A comparative study of the results of removal of meningiomas with trepanation of the canals (main group) or without it (control group) was carried out among patients with the most critical vision situation (visual acuity 0.1 and below, up to only light perception). These groups are comparable in the number of observations - 62 and 73 respectively. The predominance of cases with improved vision in the main group compared with the control group (50.0% versus 38.36%) and a lower incidence of vision impairment (22.58% versus 34.25%) were found. However, the revealed differences are statistically unreliable and make it possible for us to talk only about the trend. The complications associated with trepanation of the canal include mechanical damage to the nerve by the drill. In our series of observations, there was only 1 case of abrasion of the nerve surface with the burr, which did not lead to a significant visual impairment. With the intradural method of trepanation in the area of the medial wall of the canal, the sphenoid sinus may open (in our series, in 34 cases out of 160 trepanations). Immediately closure of these defects was performed by various auto- and allomaterials in various combinations (pericranium, fascia, muscle fragment, hemostatic materials, and fibrin-thrombin glue). A true complication - CSF rhinorrhea liquorrhea developed in only one case, which required transnasal plastic surgery of the CSF fistula using a mucoperiostal flap.

CONCLUSIONS

1. Trepanation of the optic canal in cases of meningiomas of parasellar localization is a relatively safe procedure in the hands of a trained neurosurgeon and does not worsen the results of operations compared with the excision of the same tumors without trepanation of the canal. 2. The literature data and the results of our study make it possible to consider the decompression of the optic canal as an optional, but in many cases, useful option that facilitates the transcranial removal of some meningiomas of the sellar region.

Biportal endoscopic transorbital approach: a quantitative anatomical study and clinical application

BACKGROUND

We devised a biportal endoscopic transorbital approach (BiETOA) to gain surgical freedom by making a port for the endoscope and investigated the benefits and limitations of BiETOA.

METHODS

A cylindrical port was designed and 3-D printed using biocompatible material. The port was inserted through a keyhole between the superolateral side of the orbital rim and the temporal muscle. An endoscope was inserted through the port, and other instruments were inserted through the conventional transorbital route. BiETOA was used to dissect eight cadaveric heads, and the angle of attack and surgical freedom were assessed.

RESULTS

The mean maximal angle of attack was significantly different in BiETOA and endoscopic transorbital approach (ETOA) (P < 0.01) but not in BiETOA and ETOA lateral orbital rim (LOR) osteotomy (P = 0.207, P = 0.21). The mean surgical freedom was significantly different in BiETOA and ETOA (P < 0.01) and in BiETOA and ETOA LOR osteotomy (P < 0.01). In the clinical cases, tumors were removed successfully without any complications.

CONCLUSIONS

BiETOA provided increased surgical freedom and better visibility of deep target lesion and resulted in good surgical and cosmetic outcomes.

Hemorrhagic Fibrous Dysplasia with Acute Neurological Decline: Case Report and Review of the Literature

BACKGROUND

Fibrous dysplasia is a rare, benign fibro-osseous malformation whose occurrence in the craniofacial area can result in optic nerve compression, a cerebral mass effect, and cosmetic deformity. Most lesions will progress slowly, and the risk of malignant progression is rare.

CASE DESCRIPTION

We present the case of a 21-year-old woman who had presented with acute worsening visual loss secondary to hemorrhagic fibrous dysplasia with ensuing optic nerve compression. Emergent surgical decompression resulted in rapid improvement of her visual dysfunction. The pathological features demonstrated a mixed pattern of woven bone in a fibrous background and secondary aneurysmal bone cyst-like changes.

CONCLUSIONS

Hemorrhagic transformation of craniofacial FD remains rare but can present with acute neurologic deterioration. Rapid diagnosis and treatment can allow reversal of patient morbidity. We have also included Supplementary Video 1 to illustrate the surgical principles, and we review the reported data of similar cases.

Endoscopic endo- and extra-orbital corridors for spheno-orbital region: anatomic study with illustrative case

BACKGROUND AND OBJECTIVE

Management of selected spheno-orbital meningiomas via the endoscopic transorbital route has been reported. Surgical maneuverability in a narrow corridor as that offered by the orbit may be challenging. We investigate the additional use of an extra-orbital (EXO) path to be used in combination with the endo-orbital (EO) corridor.

MATERIAL AND METHODS

Three human cadaveric heads (six orbits) were dissected at the Laboratory of Surgical Neuroanatomy at the University of Barcelona. The superior eyelid endoscopic transorbital approach was adopted, introducing surgical instruments via both corridors. Surgical freedom analysis was run to determine directionality of each corridor and to calculate the surgical maneuverability related to three anatomic targets: superior orbital fissure (SOF), foramen rotundum (FR), and foramen ovale (FO). We also reported of a 37-year-old woman with a spheno-orbital meningioma with hyperostosis of the lateral wall of the right orbit, treated with such combined endo-orbital and extra-orbital endoscopic approach.

RESULTS

Combining both endo-orbital and extra-orbital corridors permitted a greater surgical freedom for all the targets compared with the surgical freedom of each corridor alone (EO + EXO to SOF: 3603.8 mm² ± 2452.5 mm²; EO + EXO to FR: 1533.0 mm² ± 892.2 mm²; EO + EXO to FO: 1193.9 mm² ± 782.6 mm²). Analyzing the extra-orbital pathway, our results showed that the greatest surgical freedom was gained in the most medial portion of the considered area, namely the SOF (1180.5 mm² ± 648.3 mm²). Regarding the surgical case, using both pathways, we gained enough maneuverability to nearly achieve total resection with no postoperative complications.

CONCLUSION

An extra-orbital corridor may be useful to increase the instruments' maneuverability, during a pure endoscopic superior eyelid approach, and to reach the most medial portion of the surgical field from a lateral-to-medial trajectory. Further studies are needed to better define the proper indications for such strategy.

Defining the lateral limits of the endoscopic endonasal transtuberculum transplanum approach: anatomical study with pertinent quantitative analysis

OBJECTIVE

The extended endoscopic endonasal transtuberculum transplanum approach is currently used for the surgical treatment of selected midline anterior skull base lesions. Nevertheless, the possibility of accessing the lateral aspects of the planum sphenoidale could represent a limitation for such an approach. To the authors' knowledge, a clear definition of the eventual anatomical boundaries has not been delineated. Hence, the present study aimed to detail and quantify the maximum amount of bone removal over the planum sphenoidale required via the endonasal pathway to achieve the most lateral extension of such a corridor and to evaluate the relative surgical freedom.

METHODS

Six human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. The laboratory rehearsals were run as follows: 1) preliminary predissection CT scans, 2) the endoscopic endonasal transtuberculum transplanum approach (lateral limit: medial optocarotid recess) followed by postdissection CT scans, 3) maximum lateral extension of the transtuberculum transplanum approach followed by postdissection CT scans, and 4) bone removal and surgical freedom analysis (a nonpaired Student t-test). A conventional subfrontal bilateral approach was used to evaluate, from above, the bone removal from the planum sphenoidale and the lateral limit of the endonasal route.

RESULTS

The endoscopic endonasal transtuberculum transplanum approach was extended at its maximum lateral aspect in the lateral portion of the anterior skull base, removing the bone above the optic prominence, that is, the medial portion of the lesser sphenoid wing, including the anterior clinoid process. As expected, a greater bone removal volume was obtained compared with the approach when bone removal is limited to the medial optocarotid recess (average 533.45 vs 296.07 mm2; p < 0.01). The anteroposterior diameter was an average of 8.1 vs 15.78 mm, and the laterolateral diameter was an average of 18.77 vs 44.54 mm (p < 0.01). The neurovascular contents of this area were exposed up to the insular segment of the middle cerebral artery. The surgical freedom analysis revealed a possible increased lateral maneuverability of instruments inserted in the contralateral nostril compared with a midline target (average 384.11 vs 235.31 mm2; p < 0.05).

CONCLUSIONS

Bone removal from the medial aspect of the lesser sphenoid wing, including the anterior clinoid process, may increase the exposure and surgical freedom of the extended endoscopic endonasal transtuberculum transplanum approach over the lateral segment of the anterior skull base. Although this study represents a preliminary anatomical investigation, it could be useful to refine the indications and limitations of the endoscopic endonasal corridor for the surgical management of skull base lesions involving the lateral portion of the planum sphenoidale.