Turkish Neurosurgery
Medial pontine area: Safe entry to the brainstem as a cut above the rest
Abdullah Emre Taçyıldız1, Ozan Barut2, Melih Üçer3, Yaser Özgündüz2, Necmettin Tanrıöver4
1Karabük University Faculty of Medicine, Neurosurgery , Karabük,
2Istanbul University, Cerrahpasa Medical Faculty, Microsurgical Neuroanatomy Laboratory, Neurosurgery, İstanbul,
3Biruni University Faculty of Medicine, Neurosurgery, İstanbul,
4Istanbul University, Cerrahpasa Medical Faculty, Neurosurgery, İstanbul,
DOI: 10.5137/1019-5149.JTN.45710-23.1

Aim:The safe entry zones for ventral brainstem (BS) should ideally be away from the cranial nerve fibers and their nuclei, contain the least amount of fibers, and should be apart from the functional descending and ascending tracts. Specifically, the management of intrinsic lesions located along the anterior surface of the pons has still been controversial, challenging, and worrisome. Our study aims to revisit the fiber-based anatomy of the medial pontine area (MPA), what is presumed to be one of the most commonly used BS safe entry zones in neurosurgery. Material and Methods:The six brainstems were kept in 10% formalin solution for at least two months in accordance with the protocol proposed by Klingler J. and Ludwig E. After the arachnoid mater, pia mater, and vascular structures were removed, samples were frozen at -16°C for at least two weeks. White matter (WM) pathways of the BS were explored by gradually using fiber dissections under the surgical microscope. Results:Safe entry zones of the BS were defined and explored with special emphasis on the ventral pontine region and pontomesancephalic junction. The MPA formed a safe surgical field due to the distinct nature of scarcity of fibers on the anterior surface of the pons. MPA’s perfect location in between the descending corticospinal tracts and its secure depth back to the anterior limit of the medial lemniscus constructed a surgical asylum for BS safe entry zones. Conclusion:The pivotal position of the MPA has the potential to offer a combined surgical path with superiorly located BS entry zones, thus creating a wider surgical area. Entry to the BS through the MPA increases the surface area that can be accessed in the ventral pons and can be combined with the other described perioculomotor safe regions. Our study may prove helpful for endoscopic endonasal transclival interventions to intrinsic pontine lesions safer.

Corresponding author : Abdullah Emre Taçyıldız