Angiographic Demonstration of a Transverse Sinus Fenestration Coexisting with a Kobayashi Type 4B Torcular Variant: Case Report.

This report describes an exceptionally rare case of an incidental angiographic fenestration of a dominant right transverse sinus (TS) associated with a Kobayashi type 4B torcular variant in a 54-year-old patient who presented with a coexisting intracranial arterial aneurysm. While TS fenestrations are known from cadaveric studies and non-invasive imaging, high-resolution dynamic digital subtraction angiography (DSA) documentation of an isolated TS fenestration in vivo remains exceptionally scarce in the literature. The patient initially underwent computed tomography angiography (CTA), which identified the arterial aneurysm and a suspicious image in the right TS. Subsequently, a DSA was performed for definitive neurovascular evaluation. While the arterial phase characterized the aneurysm, the late venous phase incidentally revealed a TS fenestration, coexisting with a Kobayashi type 4B torcular configuration. This case underscores the importance of a meticulous evaluation of the cerebral venous phase during DSA. Precise knowledge of this dual-lumen dural variant is critical for neurosurgeons and neurointerventionalists, as its presence on the hemodynamically dominant side significantly influences surgical corridors and endovascular navigation strategies required to manage concurrent neurovascular pathologies safely.