Assessment of the inferior petrosal sinus on T1‑weighted contrast‑enhanced magnetic resonance imaging

Context: Skull base venous anatomy. Aims: While prior studies have focused on the efficacy of conventional fluoroscopic venography and multidetector computed tomography venography to evaluate the inferior petrosal sinus (IPS) before image‑guided intervention (such as dural venous sinus sampling), we believe that routine magnetic resonance imaging (MRI) may provide reliable structural information helpful for planning without the need for further imaging. Settings and Design: Retrospective review of brain MRI. Materials and Methods: Retrospective analysis was carried out on IPSs on contrast‑enhanced T1‑weighted MR images. Qualitative measurements were made regarding the grade of patency of the IPS, variation in IPS drainage pattern, and grading of the ipsilateral transverse and sigmoid sinuses (TS and SS). Statistical Analysis Used: Pearson's product‑moment correlation. Results: Evaluation of a total of 148 IPSs revealed that 91% of cases were grade 3 or grade 2 (either fully or mostly visualized), with 65% of cases demonstrating “typical” (type A) drainage directly into the internal jugular vein and no statistically significant correlation between the patency of the IPS and the dominance of the ipsilateral TS/SS. A bilateral concordance rate of 77% was also observed. Conclusions: Our analysis indicates that routine thin‑slice contrast‑enhanced T1‑weighted MRI can provide sufficient anatomic detail to identify typical drainage pattern of the IPS in a majority of cases. In cases where routine drainage was not identified, spatial resolution was not sufficient to further delineate complex drainage anatomy. No correlation was observed between the TS/SS dominance and patency of the ipsilateral IPS.