Using the Endoscopic Endonasal Transclival Approach to Access Aneurysms Arising from AICA, PICA, and Vertebral Artery: An Anatomical Study

A standalone minimally invasive presigmoid retrolabyrinthine suprameatal approach: A cadaveric morphometric study

Background

Presigmoid approaches provide access to several structures anterior to the sigmoid sinus (SS) and may be intended for the treatment of lesions located in the middle and posterior fossa. We conducted a morphometric cadaveric study investigating the infratentorial presigmoid retrolabyrinthine suprameatal approach (PRSA) as a unique operative corridor. The typical anatomic-radiological characteristics and variations were evaluated and analyzed to predict surgical accessibility.

Methods

A total of 10 surgical dissections were performed on both sides of five adults, injected, and cadaveric heads. Fifteen morphometric parameters were measured, analyzed, and categorized into pre-procedural, intra-procedural, and additional parameters.

Results

Preoperative anatomic-radiological parameters provide valuable information to select patients with favorable anatomy that may offer appropriate surgical accessibility to the medial part of cerebellopontine angle cistern, lateral pons, and prepontine cistern through a PRSA corridor. An obtuse petroclival angle of ≥144° with a more horizontally oriented petrous bone, a posterior SS position, and a large mastoid cavity provided the greatest surgical accessibility through the PRSA corridor. The superior petrosal sinus drainage and the degree of petrous apex pneumatization were important factors affecting surgical fluency and speed. However, they were not determinant factors for selecting the most appropriate patients eligible for the PRSA.

Conclusion

The PRSA represents a minimally invasive modification of the trans-labyrinthine approach that may be offered in patients with lesions medial to the internal auditory canal or anterior/lateral to the brainstem, with the goal of preserving vestibulocochlear functions. Preoperative anatomic-radiological parameters are mandatory for a patient-tailored selection of the most effective surgical approach.

Minimally invasive presigmoid retrolabyrinthine suprameatal approach (PRSA): A cadaveric study for accessing premeatal anterior inferior cerebellar artery (AICA) aneurysms

Background

The surgical management of aneurysms involving the proximal third of the anterior inferior cerebellar artery (AICA) usually necessitates complex and invasive approaches, thus posing major challenges. We aimed to investigate the infratentorial presigmoid retrolabyrinthine suprameatal approach (PRSA) as a surgical corridor for premeatal AICA aneurysms.

Methods

We performed 10 PRSA dissections in five cadaveric heads. Twelve morphometric parameters were measured, analyzed, and categorized into pre-procedural, intra-procedural, and additional parameters. The typical anatomic-radiological characteristics and variations were evaluated, and the related anatomical and radiological parameters were analyzed to predict surgical accessibility.

Results

Preoperative anatomic-radiological parameters provide valuable information to select patients with favorable anatomy that may offer appropriate surgical accessibility to the premeatal AICA through a PRSA corridor. The position of the basilar artery from the midline determines the degree of accessibility to the origin of AICA through the infratentorial PRSA. The PRSA for targeting proximal AICA aneurysms was also compared to other surgical approaches based on the available current literature.

Conclusion

Premeatal AICA aneurysms can be accessed and clipped through the infratentorial PRSA corridor. This would allow surgeons to avoid the sacrifice of hearing and balance as compared to other available invasive alternative approaches. The selection of the appropriate patients should be based on the individualized preoperative radiological characteristics for both the vascular and bony anatomy.

How I do it: the endoscopic endonasal transclival approach for clipping of the ruptured vertebral artery aneurysm

BACKGROUND

Vertebral artery aneurysms account for less than 5% of all cerebral aneurysms. They have a high risk of rupture and are associated with threatening clinical outcomes compared with anterior circulation aneurysms.

METHOD

The endoscopic endonasal transclival approach (EETA) was used. During the temporary clipping, the neck of the aneurysm was dissected, and a permanent clip was applied. The repair of the skull base defect was carried out with the nasoseptal mucoperiosteal flap on the vascular pedicle.

CONCLUSION

The EETA is a feasible alternative for the clipping of the medially located ruptured vertebral artery aneurysm. EETA can be recommended for centers with a large volume of cerebrovascular and endoscopic neurosurgical procedures.

Anatomic feasibility of endoscopic endonasal intracranial aneurysm clipping: a systematic review of anatomical studies

Clinical studies have suggested the endoscopic endonasal approach (EEA) for aneurysm clipping as a feasible way to treat select intracranial aneurysms. Among neurosurgery, there is not a consensus on the utility of EEA aneurysm clipping. This review aims to define the anatomic feasibility of EEA for aneurysm clipping. Two databases (PubMed, Cochrane) were searched for anatomical studies assessing EEA for intracranial aneurysm clipping. Literature review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Quantitative anatomical studies were included. Eleven studies met inclusion criteria. Vascular exposure and clip placement on vessels of interest were possible, although only one study assessed these parameters with physical aneurysm models. Anterior circulation vessels, although accessible in over 90% of specimens, had low successful clipping rates in a small and large aneurysm models. Small and large model posterior circulation aneurysms were more readily clipped. Proximal and distal controls were readily attainable in posterior circulation aneurysms, but not anterior. This current literature review highlights the relevance of anatomical studies in assessing the feasibility of the EEA for clipping intracranial aneurysms. As such, anterior circulation aneurysms are poor candidates for EEA given difficulties in clip placement and obtaining proximal control and distal control in small and large aneurysms. While our results suggest that clipping of posterior circulation aneurysms is feasible from a technical stand of view, further clinical experience is required to assess its feasibility in terms of safety and efficacy, balancing the indications with endovascular treatment options.

Microsurgical Anatomy of the Inferior Petroclival Vein and its Relation to Surrounding Structures: A Cadaveric and Radiological Study

BACKGROUND

The inferior petroclival vein (IPV) courses along the extracranial surface of the petroclival fissure. It is occasionally involved in vascular diseases and has recently been used for vascular access to the cavernous sinus. However, detailed descriptions of its anatomy are currently lacking.

OBJECTIVE

To define the anatomic relationship between the IPV and its surrounding structures based on cadaveric dissection and radiological analysis.

METHODS

A dry skull and an injected cadaver head were examined to reveal the relationships between the IPV and its surrounding structures. The existence of the IPV and its relationships with other venous structures were also examined by contrast-enhanced, fat-suppressed T1-weighted magnetic resonance imaging in 26 patients (51 sides).

RESULTS

The entire course of the IPV was shown via stepwise cadaver dissection from below. Its relationships with surrounding structures, such as the jugular bulb, sigmoid sinus, inferior petrosal sinus, petrosal venous confluence, and the posterior, lateral, and anterior condylar veins, were also shown. In the radiological analysis, the IPV was identified on all sides. The rostral end of the vein was connected to the venous plexus around the carotid artery on all sides. The vein drained into the caudal end of the inferior petrosal sinus (49/51 sides, 96.1%) or into the anterior condylar vein (2/51 sides, 3.9%).

CONCLUSION

A precise understanding of the anatomy of the IPV will enable endovascular and skull base surgeons to achieve diagnoses and gain safe access to lesions involving the IPV.

Endoscopic Endonasal Approach for Clipping Anterior Communicating Artery Aneurysms From Cadaver Studies and Three-Dimensional Printed Models to a Clinical Case

OBJECTIVES

Anterior communicating artery (ACoA) aneurysm is one of the most common intracranial aneurysms, and it is also the aneurysm with the highest rupture rate. With the improvement of endoscopic techniques, it is possible to use an endoscopic endonasal approach (EEA) to clip ACoA aneurysms. For further analysis of the EEA for clipping ACoA aneurysms, we used cadaver heads and three-dimensional (3D)-printed models to finish the anatomical study, and we finally selected 1 clinical case to complete the clipping through the EEA.

MATERIALS AND METHODS

We first collected 3 cadaver heads to simulate the EEA. Then, the imaging data of 29 real cases of ACoA aneurysm were collected, and the model of an aneurysm was prepared by 3D printing technology; then, the EEA was used to simulate the clipping of the aneurysm model. Finally, a clinical case with 2 ACoA aneurysms was selected to adopt the EEA for clipping.

RESULTS

Both the cadaver head and 3D-printed aneurysm model could simulate aneurysm clipping with the EEA. The clinical case of the selected ACoA aneurysm can successfully complete the clipping through the EEA.

CONCLUSIONS

3D-printed models are a good method to study the anatomical characteristics of a surgical approach. For specially selected ACoA aneurysms, the EEA is relatively simple method that can be used to clip the aneurysm successfully. The EEA for clipping ACoA aneurysms is a useful complement to the current traditional craniotomy approaches and endovascular embolization.

Extended Endoscopic Endonasal Clipping of Intracranial Aneurysms: An Anatomic Feasibility Study

BACKGROUND

Intracranial aneurysms (IAs) located in the midline region represent formidable challenge owing to their deep location. The objective of this study was to assess feasibility and identify the limitations of endoscopic endonasal clipping of IAs. We further aimed to describe the locations and characteristics of aneurysms that may be amenable for endoscopic endonasal clipping; thus outlining the indications of these approaches.

METHODS

Fifteen latex-injected cadaveric heads were used for endoscopic endonasal exposure of anterior and posterior cerebral circulations. An aneurysm simulator model with 2 different sizes was used at the common sites for IAs to emulate a real surgery. Key measured parameters included "exposure of vessels and their respective perforators," "ability to gain proximal/distal control," and "possibility of clip placement" according to the size, direction, and location of the aneurysm model. Maneuverability of instruments and the need for pituitary gland transposition were assessed and recorded as well.

RESULTS

Exposure of the anterior communicating artery complex and the common sites of posterior circulation aneurysms were feasible. The size, location, and direction of the aneurysm model had an impact on obtaining proximal and/or distal control, and the ability of clip placement.

CONCLUSIONS

Clipping of midline aneurysms of the posterior circulation is feasible via endoscopic endonasal approach. Small-sized ventrally and medially directed aneurysm models carried a better probability of getting proximal and/or distal control, as well as better overall ability to place a clip. The endonasal route seems to provide a limited condition for proper management of anterior circulation aneurysms.

Assessment of the endoscopic endonasal approach to the basilar apex region for aneurysm clipping

OBJECTIVE

The expanded endoscopic endonasal approach (EEA) has shown promising results in treatment of midline skull base lesions. Several case reports exist on the utilization of the EEA for treatment of aneurysms. However, a comparison of this approach with the classic transcranial orbitozygomatic approach to the basilar apex (BAX) region is missing.The present study summarizes the results of a series of cadaveric surgical simulations for assessment of the EEA to the BAX region for aneurysm clipping and its comparison with the transcranial orbitozygomatic approach as one of the most common approaches used to treat BAX aneurysms.

METHODS

Fifteen cadaveric specimens underwent bilateral orbitozygomatic craniotomies as well as an EEA (first without a pituitary transposition [PT] and then with a PT) to expose the BAX. The following variables were measured, recorded, and compared between the orbitozygomatic approach and the EEA: 1) number of perforating arteries counted on bilateral posterior cerebral arteries (PCAs); 2) exposure and clipping lengths of the PCAs, superior cerebellar arteries (SCAs), and proximal basilar artery; and 3) surgical area of exposure in the BAX region.

RESULTS

Except for the proximal basilar artery exposure and clipping, the orbitozygomatic approach provided statistically significantly greater values for vascular exposure and control in the BAX region (i.e., exposure and clipping of ipsilateral and contralateral SCAs and PCAs). The EEA with PT was significantly better in exposing and clipping bilateral PCAs compared to EEA without a PT, but not in terms of other measured variables. The surgical area of exposure and PCA perforator counts were not significantly different between the 3 approaches. The EEA provided better exposure and control if the BAX was located ≥ 4 mm inferior to the dorsum sellae.

CONCLUSIONS

For BAX aneurysms located in the retrosellar area, PT is usually required to obtain improved exposure and control for the bilateral PCAs. However, the transcranial approach is generally superior to both endoscopic approaches for accessing the BAX region. Considering the superior exposure of the proximal basilar artery obtained with the EEA, it could be a viable option when surgical treatment is considered for a low-lying BAX or mid-basilar trunk aneurysms (≥ 4 mm inferior to dorsum sellae).

Analysis of anterior and posterior maneuvers to enhance intraconal exposure

BACKGROUND

The medial and inferior recti encompass the ideal surgical corridor to approach the intraconal space endonasally. Here, we describe 3 different maneuvers to achieve greater access to orbital contents through an expanded endonasal approach (EEA).

METHODS

Four human cadaver heads were dissected bilaterally (n = 8). EEA to the medial intraconal orbit was executed. The following 3 maneuvers were performed: (1) anterior: extraocular muscles control (EOM); (2) posterior: annulus of Zinn (AZ) release; and (3) anterior/posterior combined. Measurements of the inferior and medial rectus corridor at the level of anterior ethmoidal artery (AEA) and posterior ethmoidal artery (PEA) and extent of optic nerve and medial rectus visualization was performed before and after each maneuver.

RESULTS

Medial rectus length (MRL) and optic nerve length (ONL) achieved were 1.72 ± 0.28 cm and 0.85 ± 0.2 cm, respectively. Mean caudal-rostral distances between the rectus muscles at the level of the AEA and PEA were 3.45 ± 0.7 mm and 1.30 ± 0.3 mm, respectively. After EOM control, mean caudal-rostral distances at the same level were as follows: AEA 4.90 ± 1.15 mm (p = 0.009) and PEA 1.70 ± 0.20 mm (p = 0.016). With AZ release, MRL was 2.20 ± 0.7 cm (p = 0.002) and ONL was 1.30 ± 0.2 cm (p = 0.003), with mean rostral-caudal distance at the level of AEA at 4.03 ± 0.8 mm (p = 0.16) and PEA at 1.71 ± 0.36 mm (p = 0.039). Mean caudal-rostral distances achieved with AZ release and EOM control were as follows: AEA 5.6 ± 1.2 mm (p = 0.001) and PEA 2.15 ± 0.4 mm (p = 0.001).

CONCLUSION

Progressive access to the orbital contents is afforded with the 3 delineated maneuvers. The magnitude of access is optimized with the combined maneuver. The actual anterior/posterior location of the target will determine which maneuvers are required.

Feasibility of endoscopic endonasal approach for clip application of cerebral aneurysms: a systematic review

INTRODUCTION

While open, microsurgical clipping and endovascular coiling remain the gold standards for treatment of cerebral aneurysms, a growing number of aneurysms treated via endoscopic endonasal methods have been reported in the literature. The aim of this study was to conduct a systematic review of the literature to gain a more thorough appreciation of the potential benefits and drawbacks of the endoscopic endonasal strategy in this setting.

EVIDENCE ACQUISITION

We performed a detailed systematic review of the medical literature on endoscopic endonasal skull base surgery for treatment of cerebral aneurysms utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We identified 9 clinical studies describing treatment of 23 aneurysms utilizing the EEA. Eleven additional cadaveric studies investigating aspects of operative exposure and/or technique in this setting were identified. The full text of these articles was reviewed.

EVIDENCE SYNTHESIS

In the 9 clinical studies that met inclusion criteria, 23 aneurysms were treated in 21 patients. The mean patient age was 52.6 years. 15 aneurysms were unruptured and 8 were ruptured. Fourteen aneurysms involved the anterior circulation and 9 involved the posterior circulation. In 21 of 23 aneurysms, complete occlusion was achieved with endonasal clipping. Two aneurysms required additional treatment that included a takeback for clip repositioning and staged endovascular coiling. Complications included post-operative CSF leak (23.8%), stroke (19%), and meningitis (14.3%). Analysis of the combined literature revealed a significantly higher rate of CSF leak with endonasal clipping of posterior circulation aneurysms compared to anterior circulation aneurysms (P=0.047, Fisher's Exact Test). While there was a trend towards increased post-operative neurologic deficit following EEA for posterior circulation aneurysms, this did not reach statistical significance (P=0.063). The majority of post-operative complications in posterior circulation aneurysms occurred during clip application of aneurysms at the level of the basilar apex. In addition to the aforementioned clinical reports, 11 cadaveric studies were identified. 4 of these reports investigated approaches for individual anterior circulation aneurysms, 5 investigated approaches for posterior circulations aneurysms, and 2 involved both anterior and posterior circulation aneurysms.

CONCLUSIONS

Despite a moderate increase in utilization, caution should be exercised when choosing an endonasal strategy for treatment of aneurysmal pathology over more traditional and established methods such as microsurgical clip application and endovascular methods. Anecdotal evidence suggests that inferior and/or medial projecting aneurysms involving the paraclinoid ICA not amenable to traditional open/endovascular strategies may be reasonable to consider for EEA clip application. Wide-necked, midline, ventrolaterally-projecting aneurysms involving the vertebrobasilar system may represent an additional exception, as long as the location along the rostrocaudal axis is low enough so as not to compromise visualization. Future improvements in operative technology, including anticipated advances in endoscopic 3-D visualization, may further alter the landscape of treatment involving this complex pathology.