2025 Poster Presentations
P379: INCIDENCE OF DOMINANT OCCIPITAL SINUS VARIANTS AND ITS IMPLICATIONS DURING THE MICROSURGICAL MANAGEMENT OF POSTERIOR FOSSA SKULL BASE LESIONS: CASE ILLUSTRATIONS AND RESULTS FROM THE ANALYSIS OF 430 CEREBRAL ANGIOGRAMS AND MAGNETIC RESONANCE VENOGRAMS.
Varadaraya S. Shenoy, MD1; Craig Heflick, MS2; Satyanarayana Shenoy, MD3; Basavaraj Ghodke, MD1; Laligam N. Sekhar, MD1; 1Harborview Medical Center, University of Washington, Seattle; 2WSU Elson S. Floyd College of Medicine; 3Tarun Neuro Clinic, Thane - 400604
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Introduction and objective: Dominant occipital sinus (OS) variants can limit the operartive corridor to posterior fossa lesions as they cannot be sacrificed. Inadvertant injury to a dominant OS can lead to fatal hemorrhage. We report the incidence and surgical strategies to circumvent dominant occipital sinus variants while approaching posterior skull base lesions.
Methods: We studied posterior fossa dural venous anatomy in 430 consecutive adult patients by analyzing cerebral angiograms and 3D magnetic resonance venograms. Patients with venous sinus thrombosis were excluded.
Results: Overall 22 cases of dominant occipital sinus variants (incidence = 5.1%) were identified out of which majority (77%, 17/22) were oblique dominant OS deviating to either side to join the jugular bulb directly. Most (76%, 13/17) of the oblique dominant OS deviated to the right side. Midline dominant occipital sinus with co-dominant marginal sinus at the foramen magnum was seen in 5 cases (23%, 5/22). Two cases of fenestrated dominant OS were seen. We describe modified dural incisions to circumvent dominant OS variants during posterior skull base surgery (Figure) using multiple case illustrations.
Conclusion: 'Dominant' occipital sinus variants has an incidence of 5.1% in adults. Pre-operative planning for elective posterior fossa surgery should involve study of dural venous sinus anatomy to prevent hemorrhagic complications. We describe operative strategies to circumvent anomalous venous sinuses in the posterior fossa.