Tailoring the surgical corridor to the basilar apex in the pretemporal transcavernous approach: morphometric analyses of different neurovascular mobilization maneuvers

Sphenoparietal Sinus Transposition: Operative Technique for Optimizing Pretemporal Posterior Circulation Access While Preserving the Sylvian Venous Complex

BACKGROUND

Transsylvian approaches are a cornerstone of complex cranial operations, with wide applicability across cerebrovascular, skull base, and neuro-oncology operations. Deep lesions, especially those involving the basilar apex, midbrain, or interpeduncular fossa, require wide exposures that may be inhibited by the presence of a large complex of superficial sylvian veins (SSV) draining into the sphenoparietal sinus. This report describes technical and clinical aspects of the sphenoparietal sinus transposition (SPST) technique.

METHODS

Technical case report of the SPST technique, including a step-by-step neuroanatomic description, overview of common indications, clinical pearls and pitfalls, and illustrative case examples.

RESULTS

Once the benefits of proceeding with SPST have been established, the maneuver is initiated with 2 stepwise dural incisions: an incision from lateral to medial along the lateral margin of the lesser sphenoid wing, followed by an orthogonal cut across the temporal pole down the middle fossa floor. The pretemporal dura is peeled off the lateral wall of the cavernous sinus, allowing mobilization of the SSV complex and temporal pole posteriorly without disrupting or straining the connection point at the sphenoparietal sinus. Illustrative case examples include a clip reconstruction of a basilar apex aneurysm for which earlier endovascular treatment had failed and microsurgical resection of a peduncular cavernous malformation.

CONCLUSIONS

SPST is a simple but versatile technique with important applications in complex cranial surgery. By mobilizing the SSV complex together with its dural attachment, the transsylvian corridor can be markedly widened, allowing access to the basilar apex region and ventral midbrain.

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.

The Dolenc technique was used to clip 14 cases of ruptured basilar apex aneurysms and posterior cerebral artery aneurysms

Objective

To investigate the surgical techniques and their clinical effects for ruptured basilar artery apex and posterior cerebral aneurysms via the Dolenc approach.

Methods

We retrospectively analyzed the clinical data of 14 patients with ruptured basilar artery apex and posterior cerebral aneurysms who underwent surgical clipping by the Dolenc approach from July 2017 to June 2020 in Beijing Tiantan Hospital affiliated with Capital Medical University and Lianyungang Hospital affiliated with Xuzhou Medical University. The modified Rankin scale (mRs) scores were used to evaluate the prognosis of patients.

Results

All 14 cases of aneurysms were successfully clipped. Overall, 1, 2, and 1 cases of postoperative new-onset visual loss, oculomotor nerve palsy, and contralateral hemiplegia, respectively, were reported. Digital subtraction angiography (DSA) or computed tomography angiography (CTA) examination of the aneurysm within 2 weeks after surgery revealed that the aneurysm was completely clipped without residue. The observations during the follow-up within 12–18 months after surgery were as follows: 1 case of vision loss returned to normal, 2 cases of oculomotor nerve palsy, 1 case of return to normal, 1 case of improved, 1 case of contralateral hemiplegia improved after rehabilitation treatment, and 1 case of hydrocephalus ventriculoperitoneal shunt surgery was performed. Overall, 11, 2, and 1 case had mRs scores of 0, 1, and 2, respectively. No death was reported.

Conclusion

For the small number of basilar apical and posterior cerebral aneurysms treated non-invasively, the Dolenc approach may offer advantages over other modalities.

Comparative Anatomical Assessment of Full vs Limited Transcavernous Exposure of the Carotid-Oculomotor Window

BACKGROUND

Although the full transcavernous approach affords extensive mobilization of the oculomotor nerve (OMN) for exposure of the basilar apex and interpeduncular cistern region, this time-consuming procedure requires substantial dural dissection along the anterior middle cranial fossa.

OBJECTIVE

To quantify the extent to which limited middle fossa dural elevation affects the carotid-oculomotor window (C-OMW) surgical area during transcavernous exposure after OMN mobilization.

METHODS

Four cadaveric specimens were dissected bilaterally to study the C-OMW area afforded by the transcavernous exposure. Each specimen underwent full and limited transcavernous exposure and anterior clinoidectomy (1 procedure per side; 8 procedures). Limited exposure was defined as a dural elevation confined to the cavernous sinus. Full exposure included dural elevation over the gasserian ganglion, extending to the middle meningeal artery and lateral middle cranial fossa.

RESULTS

The C-OMW area achieved with the limited transcavernous exposure, compared with full transcavernous exposure, provided significantly less total area with OMN mobilization (22 ± 6 mm2 vs 52 ± 26 mm2, P = .03) and a smaller relative increase in area after OMN mobilization (11 ± 5 mm2 vs 36 ± 13 mm2, P = .03). The increase after OMN mobilization in the C-OMW area after OMN mobilization was 136% ± 119% with a limited exposure vs 334% ± 216% with a full exposure.

CONCLUSION

In this anatomical study, the full transcavernous exposure significantly improved OMN mobilization and C-OMW area compared with a limited transcavernous exposure. If a transcavernous exposure is pursued, the difference in the carotid-oculomotor operative corridor area achieved with a limited vs full exposure should be considered.