2025 Poster Presentations
P448: BREAKING THE IMPENETRABLE FORTRESS: THE INFRATRIGEMINAL-SUPRAFLOCCULAR APPROACH TO PONTINE LESIONS
Alex Roman1; Rudolfh Batista ARend, MS2; Bruno Peroni2; 1INCC - Instituto de Neurocirurgia e Cirurgia de Coluna; 2UFFS - Universidade Federal Fronteira Sul
Objective: Brainstem lesions have long been considered complex pathologies that may lead to permanent deficits or life-threatening complications, posing significant challenges for surgical removal. Among these lesions, intrapontine lesions are particularly challenging in the field of neurosurgery. However, with advancements in microsurgical anatomy knowledge and technology, these lesions have become more amenable to surgical treatment. In this study, the authors examine an infratrigeminal suprafloccular approach, which has shown to be a safe surgical route, resulting in fewer post-operative complications, while evaluating the anatomical nuances of the approach and route.
Methods: Twenty cadaveric brainstem specimens were analyzed to assess the anatomy, focusing on the lateral aspect of the pons. A triangular area of entrance was measured, aiming to identify a safe zone that would spare the distinct pontine nuclei, ascending sensory pathways, corticospinal, corticonuclear, and corticopontine tracts.
Results: The authors consistently analyzed twenty brainstem specimens, examining the pontine microsurgical anatomy. They measured three distinct lines, named X, Y, and Z, forming a triangle. Line X extended from the flocculus of the cerebellum to the apparent trigeminal exit in the lateral aspect of the pons. Line Y ran from the trigeminal exit in the pons to the apparent exit of the facial-vestibulocochlear complex in the far lateral aspect of the pontomedullary sulcus in the cerebellopontine fissure. Line Z represented the measurement from the vestibulocochlear complex to the flocculus of the cerebellum. The mean measurements were as follows: X = 14.41mm (range: 10mm to 20mm), Y = 13.1mm (range: 10mm to 21mm), and Z = 3mm (range: 2mm to 5mm). The mean surface area of the analyzed specimens within the Roman Triangle (formed by X, Y, and Z) was 20.1mm² (range: 10mm² to 40mm²). This area was identified as a safe zone for the entry of microsurgical approaches to intrapontine lesions, involving less retraction of the anterior pons and potentially sparing critical structures, such as the corticospinal tracts, pontine perforating arteries, tegmentum pontis, cranial nerve nuclei, substantia reticulata dorsally, and transverse pontine fibers. Microsurgical anatomical findings, combined with intraoperative monitoring, consistently demonstrated that this entry area predicted less functional instability of the analyzed tracts and resulted in fewer postoperative complications.
Conclusion: Deep-seated pontine lesions present a complex range of pathologies with a high potential for devastating outcomes, particularly those involving hemorrhage. This study identifies and describes a presumed safe entry zone that allows for the creation of a surgical corridor for biopsy or microsurgical resection of these lesions, reducing morbidity in a previously considered impenetrable region.