2026 Poster Presentations
P121: FAR LATERAL TRANSPONTOMEDULLARY SULCUS APPROACH FOR SUPRAOLIVARY PONTINE CAVERNOUS MALFORMATIONS: MICROSURGICAL ANATOMY OF THE VAGOACCESSORY SUPRAHYPOGLOSSAL TRIANGLE
Kivanc Yangi, MD1; Sahin Hanalioglu, MD, PhD2; Egemen Gok1; Hilal A Aktas, MD, PhD3; Carlos E Calderon Valero, MS1; Osman Tunc, BS1; Jack T Olson, BS1; Jarett E Prince, BS1; Kashif Qureshi, MS1; Michael T Lawton, MD1; Mark C Preul, MD1; 1Barrow Neurological Institute; 2Department of Neurosurgery, Hacettepe University Medical Faculty; 3Department of Anatomy, Hacettepe University Medical Faculty
Introduction: Anatomical triangles defined by neurovascular structures function as useful surgical landmarks, directing access to deep-seated targets. Among these, the vagoaccessory suprahypoglossal triangle (SHT), defined by the vagus nerve (CNX), lateral border of the medulla, spinal accessory nerve (CNXI), and hypoglossal nerve (CNXII), has not been systematically investigated. Its microsurgical potential as a safe and expandable pathway to the ventromedial compartment of the posterior fossa, particularly the paramedian region of the deep pons and the pontomedullary sulcus (PMS), which serves as a potential entry point for supraolivary pontine cavernous malformations (CMs), warrants comprehensive anatomical investigation. This study describes and quantitatively analyzes the anatomical boundaries, expandability, and surgical exposure of the vagoaccessory SHT with respect to its applicability in microsurgical approaches.
Methods: Five formalin-fixed, latex-injected cadaveric heads (10 sides) were dissected using the far lateral craniotomy and transpontomedullary sulcus approach. Neuronavigation-based measurements were obtained to assess triangle dimensions under standard and expanded exposures, and statistical analyses were conducted with R software (v4.4.3). Three additional specimens were dissected to illustrate relevant brainstem anatomy. Ultrahigh-resolution 7-Tesla MRI with 3D-modeling was also used to visualize the regionally associated white matter tracts.
Results: SHT is bounded superiorly by the lowest rootlet of CNX, inferiorly by CNXII, laterally by CNXI, and medially by the lateral edge of the medulla, with mean edge lengths of 31.9(18.4) mm, 9.3(6.6)mm, 29.5(13.3)mm, and 19.5(10.7) mm, respectively. Evaluation of the SHT vertex angles showed that the inferolateral and inferomedial vertices were wider, measuring 124.3(43.5)° and 104.7(42.5)°, whereas the superolateral and superomedial vertices were narrower, at 45.3(27.6)° and 85.5(45.8)°, respectively. Distance between the craniotomy centroid and the SHT centroid was calculated as 46.2(13.5)mm. Standard brainstem exposure through the SHT measured 160.9(84.3)mm², increasing to 295.4(176.7)mm² after mobilization of the retractable edges (p=0.058). The craniocaudal angle of attack was measured at 33.8(26.7)°, while the mediolateral angle of attack measured 61.2(34.0)°. SHT provides access to the V4 segment of the vertebral artery, the p1–p2 segments of the posterior inferior cerebellar artery, the inferior olivary nucleus, and the pontine underbelly. In addition, utilization of the SHT allows exposure of the PMS, posterolateral sulcus, olivary zone, and lateral medullary zone safe entry zones. During this approach, the supraolivary trajectory leads toward the central pons, in proximity to the medial and lateral lemnisci, the spinothalamic tract, the superior olivary nucleus, the trapezoid body, and the rubrospinal tract.
Conclusions: SHT represents a consistent and expandable microsurgical route to the PMS and the central pontine region. Quantitative evaluation of the vagoaccessory SHT supports its value in surgical planning for paramedian pontine lesions, particularly supraolivary CMs. Integration of microsurgical dissection with advanced MR tractography and 3D modeling provides a detailed understanding of these anatomical corridors, thereby potentially refining surgical strategies and enhancing both precision and patient outcomes.