Superior sagittal sinus

At a glance

English

Superior sagittal sinus

Latin (TA2)

Sinus sagittalis superior

System

Vein

Region

Head

Side

Single, on the midline

About the superior sagittal sinus

The superior sagittal sinus, also called the superior longitudinal sinus, runs in the midline along the attached upper margin of the falx cerebri, between the two layers of dura where the falx meets the skull. It starts at the foramen caecum in front of the crista galli and follows the inner surface of the skull backwards, grooving the frontal bone, the adjoining edges of the two parietal bones and the upper part of the occipital bone.

In cross-section it is triangular; it is slim at the front and widens steadily as it passes back. Close to the internal occipital protuberance the sinus turns to one side, usually the right, and continues as the transverse sinus of that side; it also takes part in the confluence of sinuses there. For description it is often divided into three stretches: from the foramen caecum to bregma, from bregma to lambda, and from lambda to the confluence.

Inside, the superior cerebral veins can be seen opening into it, mostly in its back part, where the veins enter against the flow, running obliquely forwards. Fibrous strands cross the lower angle of the channel, and on each side small openings lead to the lateral lacunae, irregular venous pockets in the dura; usually there is a large parietal lacuna, a smaller frontal one and an occipital one of middle size. Many cerebral veins open into these lacunae, and arachnoid granulations push up into them. The sinus also receives veins from the diploe and dura and, through the parietal foramina, from the pericranium; at its front end it may receive a vein from the nasal cavity.

Through the arachnoid granulations, cerebrospinal fluid passes into the sinus and returns to the bloodstream. Thrombosis of the superior sagittal sinus therefore raises intracranial pressure as well as causing venous infarction and seizures. The sinus is also at risk in surgery near the midline and in skull fractures over it.

Course and drainage

Begins at

Begins at the foramen caecum in front of the crista galli.

Drains into

Ends near the internal occipital protuberance by turning into a transverse sinus, usually the right, at the confluence of sinuses.

Drains

Drains the superior cerebral veins from the upper and outer surfaces of the hemispheres, the diploe, dura and pericranium, and receives cerebrospinal fluid through arachnoid granulations.