Which cerebral venous sinus is unpaired?

The superior sagittal sinus is unpaired because it runs along the midline of the brain, situated in the falx cerebri, which is a fold of the dura mater that separates the two cerebral hemispheres. This unique positioning allows it to collect blood from the superficial veins of the brain, and it drains into the transverse sinuses at the internal occipital protuberance.

In contrast, the inferior petrosal sinus, sigmoid sinus, and transverse sinus are paired structures. The inferior petrosal sinuses are located on either side of the brainstem, draining blood from the cavernous sinus into the internal jugular veins. The sigmoid sinuses also exist in pairs, and they are the continuation of the transverse sinuses as they curve down towards the internal jugular veins. The transverse sinuses are found on both sides of the skull, collecting blood from the superior sagittal sinus and the straight sinus before draining into the sigmoid sinuses.

The unpaired nature of the superior sagittal sinus is significant in terms of anatomy and clinical considerations, as its midline position means that any pathology affecting this sinus can have bilateral effects on the brain's venous drainage.