Venous sinus of Kelch: a cadaveric study with embryological insights and clinical implications

The venous sinus of Kelch (VSK) represents a rare but clinically significant venous variant of the middle cranial fossa, with very limited documentation in the existing literature. This study aimed to understand the morphology, course, and morphometry of VSK along with associated variations in the drainage pattern of the superficial middle cerebral vein (SMCV) and middle meningeal sinus (MMS). This study was conducted over the period from 2022 to 2025 at Zoram Medical College and Hospital, Aizawl, Mizoram. In the present study, VSK was observed in 9.26% of the 54 middle cranial fossae examined from 27 cadavers. Moreover, SMCV and MMS, which normally drain into either the spheno-parietal sinus or cavernous sinus, drained into VSK. From an embryological perspective, VSK can be understood as a persistent primitive tentorial sinus (PTS). The variable course and termination of PTS may also result in other reported venous variants like Spheno-basal sinus, Spheno-petrosal sinus and Petro-basal sinus, which underscore the complexity of venous adaptations influenced by hemodynamic factors. Clinically, awareness of such variants is crucial for accurate radiological interpretation and for minimising the risk of iatrogenic injury during surgical and endovascular procedures involving the middle cranial fossa. Importantly, recognition of these alternative venous pathways may have future implications in facilitating novel endovascular approaches for neuromodulation, targeted therapy, and minimally invasive access to the temporal lobe and trigeminal nerve.