Contralateral Approach to Middle Cerebral Artery Aneurysms: An Anatomical-Clinical Analysis to Improve Patient Selection

Immersive Surgical Anatomy of the Pterional Approach

The pterional approach (PA) is a versatile anterolateral neurosurgical technique that enables access to reach different structures contained in the cranial fossae. It is essential for neurosurgical practice to dominate and be familiarized with its multilayer anatomy. Recent advances in three-dimensional (3D) technology can be combined with dissections to better understand the spatial relationships between anatomical landmarks and neurovascular structures that are encountered during the surgical procedure. The present study aims to create a stereoscopic collection of volumetric models (VM) obtained from cadaveric dissections that depict the relevant anatomy and surgical techniques of the PA. Five embalmed heads and two dry skulls were used to record and simulate the PA. Relevant steps and anatomy of the PA were recorded using 3D scanning technology (e.g. photogrammetry, structured light scanner) to construct high-resolution VM. Stereoscopic images, videos, and VM were generated to demonstrate major anatomical landmarks for PA. Modifications of the standard PA, including the mini-pterional and two-part pterional approaches, were also described. The PA was divided into seven major steps: positioning, incision of the skin, dissection of skin flap, dissection of temporal fascia, craniotomy, drilling of basal structures, and dural opening. Emphasis was placed on preserving the temporal branches of the facial nerve and carefully dissecting the temporalis muscle. The interactive models presented in this article allow for clear visualization of the surgical anatomy and windows in 360-degrees and VR. This new modality of recording neuroanatomical dissections renders a closer look at every nuance of the topography experienced by our team in the laboratory. By accurately depicting essential landmarks, stereoscopy and VM can be valuable resources for anatomical education and surgical planning.

Contralateral Approach Based on a Preoperative 3-Dimensional Virtual Osteotomy Technique for Anterior Circulation Aneurysms

OBJECTIVE

Our objective was to review 15 consecutive patients with anterior circulation aneurysms managed through a contralateral approach. Individualized surgical simulation using three-dimensional (3D) imaging was adopted to enable safe performance of clipping surgery.

METHODS

Five patients had multiple intracranial aneurysms, and 10 patients had a single aneurysm on the contralateral side of the craniotomy. Preoperatively, the unique architecture of aneurysms was fully understood in their 3-dimensionality reconstructed by Mimics software. The location of the cranial bone window and the patient's head position was individually optimized using a preoperative simulation system.

RESULTS

In this cohort, 17 contralateral aneurysms showed no wall calcifications. Projections of the aneurysms were superomedial (3/17, 17.6%), medial (8/17, 47.1%), posterior (3/17, 17.6%), and superior (3/17, 17.6%). The visual similarity between the simulating scene and the operative view was excellent in 100% of the cases. Four patients were treated with a contralateral pterional approach, and the remaining 11 patients were treated with a contralateral supraorbital keyhole approach. All of them were well-clipped, except 1 blister-like aneurysm being wrapped. All 15 patients had good outcomes (mRS ≤ 3) after a mean 13 months follow-up. There were no recurrences after surgical treatment.

CONCLUSIONS

The contralateral approach for the selected anterior circulation aneurysms is feasible in experienced hands with acceptable morbidity. This approach should be the choice only under judicious case-to-case planning based on a preoperative 3D virtual osteotomy technique.