Navigating the atrium: leveraging the intraoccipital sulcus as a natural corridor for safe access. A sulcal and subcortical architectural analysis.

Objective

Lesions in or around the atrium pose a surgical challenge due to their deep location and proximity to eloquent cortical and subcortical structures. Hence, a handful of approaches have been proposed aiming to minimize parenchymal transgression while providing adequate surgical maneuverability and dexterity. To this end, the authors sought to evaluate, for the first time in the pertinent literature, the feasibility of the intraoccipital sulcus (IOS) as a natural corridor to access the atrium safely and effectively.

Methods

Twenty formalin-fixed adult cerebral hemispheres treated with the Klingler's technique were investigated. The morphology of the IOS was recorded, and the subcortical anatomy lining the corridor from the sulcal fundus to the atrium was explored through focused lateromedial white matter dissections. Additionally, 20 T2-weighted multiplanar reconstructions (MPRs) from the HCP Young Adult dataset were analyzed to quantify the "angle of attack" toward the atrium. Then the respective distances of the IOS and intraparietal sulcus (IPS) from the midline were compared to evaluate whether an IOS-based trajectory permits access to the atrial roof rather than the lateral wall. T2-weighted MR images from a cohort of 25 healthy individuals were also included to record the IOS surface anatomy, sulcal length, and fundus-to-atrium depth.

Results

The IOS was consistently recorded and found to be continuous with the IPS in most cases. Its mean length and depth were approximately 2.2 cm and 1.1 cm, respectively, and the mean sulcal fundus-to-atrium distance was 1.90 cm. MPR analysis showed that the anterior IOS segment offers an almost perpendicular trajectory to the atrium and lies medial to the IPS, thus allowing entrance to the atrial roof. The white matter transgression en route to the ventricle disrupts the fibers of the vertical occipital fasciculus while causing minimal injury to the posterior part of the sagittal stratum. The approach avoids the optic pathway since it allows entering the atrium through its roof.

Conclusions

An IOS transsulcal corridor provides a practical, safe, and effective pathway to the roof of the atrium as it minimizes transgression of eloquent fiber tracts and respects the optic radiations. Combined cadaveric and MRI evidence supports the IOS as a reliable planning landmark for selected atrial and periatrial lesions; however, prospective clinical validation is still needed.