Operation on high-lying basilar bifurcation aneurysms

Basilar apex aneurysm systematic review: Microsurgical versus endovascular treatment

BACKGROUND

Both microsurgical and endovascular techniques continued to be treatment options for basilar apex aneurysms (BAA). We conducted a systematic review to compare both treatment options in terms of both clinical and radiological outcomes.

METHODS

The PRISMA method was used to identify related articles. Data collected from each article and the two treatment approaches were compared in terms of favorable clinical outcome and complete/near complete occlusion rate. Subgroup analysis was done based on the size and the rupture status of BAA.

RESULTS

Fifty-nine (59) and 32 articles reported a measurable clinical and radiological outcome respectively. The weighted average favorable clinical outcome was significantly higher in the endovascular group (86.4% vs 79.6%, P<0.0001), while the weighted average complete/near complete occlusion rate was significantly higher in the surgical group (92.6% vs 83.8%, P<0.0001). In the subgroup analysis, the favorable clinical outcome remained significantly higher in the endovascular group for the ruptured, unruptured and giant/large BAA (P<0.001), but not in the small BAA subgroup (P=0.26). The occlusion rate remained significantly higher in the surgical group for all subgroups (P<0.001).

CONCLUSION

Treatment of BAA remains in a trade-off between favorable clinical outcome and complete or near-complete occlusion depending on the treatment modality selected. Careful selection of cases and judicial discussion between open surgical and endovascular team is warranted for treatment optimization.

Comprehensive Anatomic Assessment of the Pterional, Orbitopterional, and Orbitozygomatic Approaches for Basilar Apex Aneurysm Clipping

BACKGROUND

The pterional approach, along with its orbitopterional and orbitozygomatic extensions, is among the most common surgical approaches for tackling challenging aneurysms of the basilar artery apex (BAX). There is general consensus that the orbitozygomatic approach provides the best exposure for these lesions. However, there is little objective evidence to support approach selection for surgical treatment of BAX aneurysms.

OBJECTIVE

To compare different features regarding surgical treatment of BAX aneurysms between the pterional, orbitopterional, and orbitozygomatic approaches.

METHODS

The pterional, orbitopterional, and orbitozygomatic approaches were sequentially completed on 10 cadaveric specimens. The visibility of perforators, lengths of exposure, and safe clipping for major BAX branches, surgical area of exposure, and the surgical freedom for the BAX target were assessed.

RESULTS

The orbitopterional approach provided significantly greater values than the pterional approach in all variables, except for exposure of the bilateral P1 posterior cerebral artery (PCA) perforators. When compared to the orbitopterional approach, the orbitozygomatic approach did not provide a statistically significant increase in (1) surgical freedom through the carotid-oculomotor triangle, (2) area of exposure, (3) ipsilateral, and (4) contralateral P1 PCA perforator visibility, and (5) ipsilateral PCA exposure and (6) clipping lengths.

CONCLUSION

The orbitopterional approach provides significantly greater surgical exposure to BAX than the pterional approach. The orbitopterional approach is less invasive while providing similar surgical access to the BAX compared to the orbitozygomatic. The results of this study show that the orbitopterional approach may be optimal for the treatment of most BAX aneurysms, particularly to reduce morbidity resulting from the full orbitozygomatic approach.

Comparative Analysis of Orbitozygomatic and Subtemporal Approaches to the Basilar Apex: A Cadaveric Study

BACKGROUND

The subtemporal and orbitozygomatic approaches are the most commonly used surgical approaches for the treatment of basilar artery apex (BAX) aneurysms. Relative advantages and disadvantages are generally reported based on surgeons' experience. This study was performed to provide a detailed comparison between the subtemporal and orbitozygomatic approaches based on cadaveric dissection analysis for the treatment of BAX aneurysms.

METHODS

Subtemporal and orbitozygomatic approaches were performed on 5 cadaveric heads (10 sides), and the following variables were assessed and compared between the 2 approaches: 1) number of exposed perforators on P₁-posterior cerebral arteries (PCA); 2) lengths of exposure and clipping for bilateral PCA, superior cerebellar arteries (SCA), and basilar trunk; 3) surgical area of exposure; and 4) surgical freedom at the BAX.

RESULTS

Number of perforators exposed on P₁-PCA was not different between the subtemporal and orbitozygomatic approaches. Exposure and clipping of ipsilateral SCA and PCA were superior using the subtemporal approach, and better for contralateral SCA and PCA using the orbitozygomatic approach, all reaching statistical significance. The orbitozygomatic approach provided greater exposure and clipping length for the proximal basilar trunk. Although the surgical area of exposure was similar between the 2 approaches, the overall surgical freedom was greater in the orbitozygomatic approach.

CONCLUSIONS

The orbitozygomatic approach provides a greater number of surgical corridors to the BAX and is superior regarding multiple surgically relevant anatomic parameters. Importantly, control over the basilar trunk and over the contralateral SCA and PCA (blind spots) is superior with the orbitozygomatic approach.

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).

Microsurgical Clipping of Basilar Apex Aneurysms: A Systematic Historical Review of Approaches and their Results

OBJECTIVE

Neck clipping remains a valuable treatment option for basilar apex aneurysms, especially in those with complex morphology, such as incorporation of branching vessels or large size, and young patient age. Several approaches have proved to give effective exposure for various types of lesion morphologies. Our historic literature review from 1976 to the present systematically compares the outcomes and complications of the key surgical approaches in the treatment of basilar apex aneurysms.

METHODS

We searched PubMed for articles with at least 5 patients, data on neurologic outcome, and procedure-associated complications for the following approaches: pterional or orbitozygomatic transsylvian, subtemporal (with or without zygomatic osteotomy), pretemporal (with or without transcavernous extension), and transpetrous. n-Weighted averages for clinical outcome, aneurysm occlusion rates, morbidity, mortality, and aneurysm morphology were compared.

RESULTS

Of 35 articles selected, 2041 patients with 722 ruptured aneurysms underwent microsurgery, including 1131 transsylvian, 241 pretemporal, 375 subtemporal, and 17 transpetrous approaches. Comparing these 4 approaches in n-weighted averages, respectively, we noted good neurologic outcomes (81%, 85%, 81%, and 58%), surgical morbidity (14%, 10%, 34%, and 53%), surgical mortality (4%, 1%, 0, and 1%), and complete occlusion rates (95%, 94%, 86%, and 75%).

CONCLUSIONS

Transsylvian, pretemporal, and subtemporal approaches showed favorable neurologic outcomes at similar rates and were applied for aneurysms located between -1mm and +7mm in relation to the posterior clinoid process. The pretemporal approach was preferably applied to large and giant aneurysms with good outcome; the transsylvian approach was most frequently used for ruptured aneurysms.

Endoscopic anatomy of the intracisternal oculomotor nerve: a new segmentation based on the topography of the arachnoid membranes

The aim of our study was to investigate the detailed endoscopic anatomy of the intracisternal portion of the oculomotor nerve and to update the present knowledge of its related anatomy with the newest research on the topography of the arachnoid membrane system of the skull base.

This study was performed on 50 fresh human cadaveric specimens post-mortem not more than 72 h. In each specimen, the intracranial arterial system was injected with red gelatin solution. We used the endoscope-controlled and endoscope-assisted microsurgical techniques applied through the minimally invasive supraorbital keyhole craniotomy to perform our dissections.

We divided the intracisternal oculomotor nerve into three segments in this study. These are the interpeduncular segment, located in the interpeduncular fossa and surrounded by dens arachnoid trabeculae around the thalamoperforating arteries; the tentorial segment, located between the posterior cerebral and superior cerebellar arteries and the posterior petroclinoid fold and surrounded by the elements of the clival and tentorial arachnoid membrane groups; and the trigonal segment located on the surface of the oculomotor trigone between the posterior petroclinoid fold and the dural exit of the nerve into the cavernous sinus and surrounded by the posteriorly located membranes of the carotid membrane group.

Our findings support the more accurate understanding of the physiology of the arachnoid membrane system and the pathophysiology of space-occupying lesions in the region of the oculomotor nerve. Therefore, our results may support performing more atraumatic surgery in this area.

Endoscopic endonasal transsphenoidal "above and below" approach to the retroinfundibular area and interpeduncular cistern--cadaveric study and case illustrations

OBJECTIVE

To evaluate the feasibility of reaching the interpeduncular cistern (IC) through an endoscopic endonasal approach that leaves the pituitary gland in place.

METHODS

In a series of 10 injected cadaver heads, the transtuberculum ("above") and transclival ("below") approaches were combined, without pituitary transposition. Using 0-degree, 30-degree, and 45-degree endoscopes, the extent of overlap and if a blind spot occurred were determined. Also, the visualization of the IC was compared with the transposition of the pituitary gland approach. Nonparametric statistics were used to evaluate the results. The approach was implemented in 2 patients.

RESULTS

For both the "above" and "below" views, there was a statistically significant increase in field of view when comparing the 0-degree endoscope with either the 30-degree endoscope (P < 0.05) or the 45-degree endoscope (P < 0.05). There was no difference between the 30-degree endoscope and the 45-degree endoscope (P > 0.05) in the "below" approach, but there was a difference (P < 0.05) in the "above" approach. There was no blind spot with any combination of endoscopes. There was no practical statistically significant difference between the transposition approach and the "above and below" approach. The "above and below" approach was used successfully in 2 surgeries.

CONCLUSIONS

It is possible to work both "above" and "below" the pituitary gland to reach the IC through an endoscopic endonasal approach. The advantages are the maintenance of normal pituitary and parasellar anatomy and the minimization of the size of the skull base defect. There is no blind spot using this approach that would be revealed with a pituitary transposition. The feasibility of this approach has been confirmed in 2 patients.

Endoscopic endonasal pituitary transposition for a transdorsum sellae approach to the interpeduncular cistern

OBJECTIVE

The interpeduncular cistern, including the retroinfundibular area, is one of the most challenging regions to approach surgically. The pituitary gland and the infundibulum guard the region when an endonasal route is undertaken. Superior transposition of the pituitary gland and infundibulum is described as a functional means to access this complex region through a fully endoscopic, completely transnasal route.

METHODS

Ten consecutive patients in whom a pituitary transposition was performed during an expanded endonasal approach at the University of Pittsburgh Medical Center for resection of retroinfundibular lesions were reviewed. The series consisted of seven men and three women with a mean age of 44.4 years. Pathology consisted of four craniopharyngiomas, four chordomas, and two petroclival meningiomas.

RESULTS

Five patients (50%) underwent total resection of the tumor, three patients (30%) underwent near total resection ( > 95% removal), and two patients (20%) had partial resection of petroclival meningiomas with the goal of optic apparatus decompression. All four patients with visual deficits recovered their vision completely. There was no neurological deterioration. Eight patients had normal pituitary function preoperatively, seven of whom (87.5%) had confirmed function preservation postoperatively, with one of these patients experiencing transient diabetes insipidus. The remaining patient with a hypothalamic craniopharyngioma underwent complete resection with obligatory panhypopituitarism and diabetes insipidus.

CONCLUSION

Endoscopic endonasal transposition of the pituitary gland and its stalk can provide a valuable corridor to the retroinfundibular space and interpeduncular cistern with pituitary function preservation in the majority of patients. This approach should only be pursued once significant experience with endoscopic endonasal approaches has been acquired.

Interactive 3D stereoscopic digital-image analysis of the basilar artery bifurcation

The goal of this study was to analyze morphometrical variations of the basilar artery bifurcation (BAB), so that physicians could map out a patients anatomical structure prior to delicate neurosurgical procedures. The CT-angio files of 98 patients ranging from 12 to 78 years of age were retrieved. These files were evaluated using Gradual Angiographic Image Data Analyzer (GAIDA) software, where a new interactive three-dimensional (3D) stereoscopic visualization method was used to reconstruct computer images of the BAB complex. Subsequently the measurements of the BAB angles and BAB distances in relation to the dorsum sellae (DS), posterior clinoid processes (PCPs), and posterior biclinoid plane (PBP) were carried out. The average BAB angle was determined to be 117.7 degrees (30.93 degrees -172.2 degrees ). The three types of BAB were classified as type T with a BAB angle greater than 145 degrees (mean 154.4 degrees ), type Y for an angle being equal or less than 145 degrees but greater than 100 degrees (mean 121.5 degrees ) and type V for angles less than 100 degrees (mean 83.28 degrees ). The mean distances between BAB and DS (9.55 mm), BAB and left PCP (12.97 mm), and BAB and right PCP (13.01 mm), BAB and PBP (2.2 mm) were evaluated. Furthermore, the BAB is of great importance when examining basilar artery aneurysm development, particularly at the point of greatest hemodynamic stress, as well as the BAB distances in relation to the bony landmarks used for different approach methods in neurosurgical procedures.