Microsurgical approaches to the pineal region: anatomic and radiological principles based on the characteristics of the neurovascular structures.

backgroundThe pineal region presents considerable challenges for neurosurgical interventions owing to its deep anatomical location and the intricate network of critical neurovascular structures that encase it. The capacity to conduct effective and safe neurosurgical procedures in this area necessitates a comprehensive understanding of anatomical variations. This study aims to conduct an in-depth analysis of radiologic measurements pertinent to accessing the pineal region, alongside their supported by qualitative cadaveric dissections.

methodsThe supracerebellar infratentorial (SCIT) approach, occipital transtentorial (OT) approach, and posterior interhemispheric (PIH) approach were performed on four cadaveric heads (eight sides). All dissections were performed with the head positioned to simulate the orientation employed in the operating room. Magnetic resonance imaging (MRI) scans from 50 male to 50 female patients were also retrospectively assessed. Descriptive statistics were presented for the quantitative data.

resultsMRI analysis of 100 adult subjects revealed a mean tentorial angle of 31.5° (range: 14.4–47.7°), indicating substantial anatomical variability. Measurements from external landmarks to the pineal gland and tentorium were quantified to assist in surgical planning. The Torcular Herophili was found to exhibit variable vertical positioning, and its distance from the inion was measured radiologically. These findings were categorized into distinct morphometric types based on tentorial inclination and torcular location. Cadaveric dissections were performed in surgical positions simulating SCIT, OT, and PIH approaches, and were used to qualitatively illustrate key anatomical corridors. Each dissection demonstrated the spatial relationships among the tentorium, splenium, deep venous system, and surrounding neurovascular structures, consistent with the anatomical context of the radiologic measurements.

conclusionIn neurosurgical practice, a lesion’s location is a critical determinant in selecting the approach for addressing pineal region lesions, given the complex microsurgical anatomy and deep positioning of these structures. Additionally, conducting thorough radiologic examinations during the preoperative phase is essential in informing the choice of surgical approach. We posit that employing radiologic measurements and identifying vascular variations will lead to reduced complication rates.