Quantitative Comparison and Target-Specific Maneuverability of the Median Infratentorial Supracerebellar versus the Occipital Transtentorial Approaches to the Pineal Region

Objectives/Aims: There is a difficulty in comparing different surgical techniques that can be used to treat the same pathology, especially where complex approaches might be necessary to treat relatively rare lesions. Indeed, lesions around and of the pineal region are challenging because of their proximity to important neurovascular structures, their deep-seated location and the possible use of two different surgical corridors. The aim of this study is to quantify microsurgical exposure and the target-specific maneuvrability afforded by the median infratentorial supracerebellar versus the occipital transtentorial approaches to the pineal gland.

Methods: The infratentorial supracerebellar and occipital transtentorial approaches to the pineal region were performed in four cadaveric heads by using standard microneurosurgical technique. All specimens underwent a CT scan using a 1 × 1 and 3 × 3 mm soft and bone tissue slices. For each craniotomy, coordinates delineating superficial and deep surface exposures a well as 28 surgical targets of interest (both vascular and nervous structures) were obtained by means of a conventional navigation tool. Offline, respective superficial and deep surfaces, and corresponding operative field volumes were calculated and visualized with in-house–developed software. A maneuvrability score was defined for every surgical points of interest taking into account the superficial area, corridor height, anatomical obstacles, and lesion-centricity (range, 2 [poor maneuverability] to 9 [excellent maneuverability]).

Results: Superficial surfaces, deep surfaces (cm²) and volumes (cm³) were 8.3 (SD, 2.5), 5.7 (SD, 2.2), 33.3 (SD, 6.5), respectively, for supracerebellar infratentorial approach and 7.2 (SD, 3.3), 12.2 (SD, 6.5), 44.4 (SD, 28.5), respectively, for occipital transtentorial approach. The deep/superficial surface ratio and the surgical volume were significantly higher for the occipital transtentorial approach. Maneuvrability scores of different targets and deep exposure varied between the two approaches, especially in the inferior aspect of the quadrigeminal cistern that was better exposed and maneuvered through the occipital transtentorial approach.

Conclusion: Both median infratentorial supracerebellar and occipital transtentorial approaches are suitable to reach the pineal region; however, the occipital transtentorial approach gives overall a larger deep exposure, working volume, and might offer a better maneuverability for targets situated in the inferior aspect of the quadrigeminal cistern where the culmen of the cerebellum and the sometimes steep angle of the tentorium might render the median infratentorial supracerebellar approach less practical.