Oblique occipital sinus in neurosurgical practice: A retrospective analysis of imaging studies

The oblique occipital sinus (OOS) is a rare anatomical variation of the occipital sinus, characterized by an enlarged lumen and an oblique course toward sigmoid-jugular junction. When undetected, it might be injured during posterior fossa surgery potentially leading to life-threatening complications.

The aim of this study was to evaluate 3D high-resolution contrast-enhanced T1-weighted magnetic resonance imaging (3DT1C-MRI) utility in detection of OOS in comparison with digital subtraction angiography (DSA) - the gold standard for intracranial vascular imaging.

We retrospectively analysed imaging studies of patients hospitalized in our Neurosurgery Department who underwent both 3DT1C-MRI and DSA. Each modality was assessed for the presence of an infratentorial obliquely oriented enlarged venous structure consistent with OOS characteristics. Imaging results were compared to determine whether the structure was detectable on both modalities or only on one.

A total of 100 patients met the inclusion criteria. OOS was initially suspected in seven cases (7%), but after consensus review, true OOS was confirmed in two cases (2%). In both confirmed cases, OOS was clearly visualized on 3DT1C-MRI, but only in one case on DSA.

OOS is an uncommon but clinically significant anatomical variant that may pose a serious threat during posterior fossa surgery. Our findings suggest that 3DT1C-MRI is not inferior to DSA in terms of OOS detection and may serve as an adequate preoperative imaging tool. Larger studies are needed to confirm these preliminary results.