Superior sagittal sinus

Origin and course

The superior sagittal sinus is an unpaired sinus that runs through the groove for superior sagittal sinus. This groove spans across the midline on the internal surface of the calvaria. The superior sagittal sinus begins anteriorly close to the crista galli of the ethmoid bone where it occasionally receives an emissary vein from the nasal cavity through the foramen cecum of the frontal bone. It then courses through the root of the falx cerebri, between the periosteal and meningeal layers of this dural infolding. It terminates posteriorly at the confluence of sinuses, close to the internal occipital protuberance. In cross-section, the superior sagittal sinus appears triangular with its apex pointing inferiorly and continuing downward as the falx cerebri. The sinus is narrow anteriorly and widens as it runs posteriorly.

Tributaries

On either side of the superior sagittal sinus are lateral expansions within the dura mater referred to as the lateral venous lacunae. There are typically two or three of them on each side; a small frontal, a large parietal and an intermediate occipital lacunae. The lacunae communicate with the sagittal sinus through small slit-like openings and often become confluent (single large lacuna) in the elderly.

The lateral venous lacunae mostly receive the diploic veins of the skull and meningeal veins. Present within the lacunae are the arachnoid granulations, which are projections of the arachnoid membrane that allow the return of cerebrospinal fluid from the subarachnoid space to the venous circulation.

Typically, along its midsection, the superior sagittal sinus may have luminal band-like projections at varying areas that arise from its dural walls. These projections separate the lumen of the sinus into superior and inferior channels. Along its course, the superior sagittal sinus receives the superior cerebral veins, the largest of which is the superior anastomotic vein (of Trolard). Additionally, emissary veins from the pericranium drain into the posterior end of the sinus through the parietal foramina of the parietal bones.

To learn more about the dural sinuses of the brain, explore our articles, quizzes, video tutorials and labelled diagrams.

Anatomical variations

The calibre of the superior sagittal sinus is usually between 3.0 to 4.5 mm while its length ranges from 24 to 27 cm. Major anatomical variations of the superior sagittal sinus are rare. The commonest reported variation is hypoplasia of its rostral end which occurs in about 7% of individuals.