The Anatomy of the Superior Sagittal Sinus
Medically reviewed by Huma Sheikh, MD
Just as veins carry blood from the body back to the lungs to be oxygenated, there are a number of vessels called sinuses that help carry blood and other fluids away from the brain. The superior sagittal sinus is one of these vessels. It collects fluids from smaller ducts, carrying them to the jugular vein for transport to the heart and lungs. The sinus system is similar to the venous system, with a few key differences.
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Anatomy
The drainage system in the brain is a complex series of vessels and ducts that carries blood and fluid away from the brain after delivering oxygen and nutrients to cerebral tissues. Tiny veins throughout the cerebrum, cerebellum, and brain stem empty into the dural venous sinuses.
The dural venous sinuses are nestled in the dura mater, a protective membrane that surrounds the brain. Excess fluids that have been used to supply the central nervous system, face, and scalp with oxygen and nutrients collect here. Once collected in the dural venous sinuses, the fluids drain to the internal jugular vein to be carried back to the pulmonary system, where they will be replenished.
Related: How Your Circulatory System Works
Structure
The dural venous sinuses include a number of sinuses, including the:
Straight sagittal sinus
Superior sagittal sinus
Inferior sagittal sinus
Transverse sinus
Sigmoid sinus
Cavernous sinus
Superior petrosal sinus
Inferior petrosal sinus
The superior sagittal sinus is the largest of the sagittal sinuses. A midline vein with no valves, it begins as a narrow vessel and expands as it extends to the back of the skull. The diameter of the superior sagittal sinus is roughly 3 millimeters–4.5 millimeters (mm), and it is about 24 centimeters–27 centimeters (cm) in total length.
Location
The superior sagittal sinus begins where the frontal and ethmoid bones meet, at the front of your face near your eyes. It is the largest dural venous sinus, and its size and prominent location at the front of the skull make it susceptible to traumatic injury. From the front of the skull, the superior sagittal sinus moves along the superior cranial vault to the falx cerebri.
The falx cerebri is formed from the dura mater and connects drainage systems and other structures where the two sides of the brain meet. Here, the straight, superior, and inferior sagittal sinuses come together in an area called the confluence of sinuses, which drains into the left and right transverse sinuses, through the sigmoid sinus, and on to the internal jugular vein.
Related: Dural Sinus Thrombosis and Stroke
Anatomical Variations
Anatomical variations of any significance are rare when it comes to the superior sagittal sinus. When variations do occur, they are generally in the size or location of the vessel:
The superior sagittal sinus usually runs midline, or along the center groove of the brain that separates the two hemispheres. However, the vessel can be up to 1 cm or more off center in about 20% of the population.
Hypoplasia, or underdevelopment, is another variation of the superior sagittal sinus found in about 7% of the population. This is most common in the sections that are found in the front or back thirds, rather than the center of the vessel.
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Function
The purpose of the superior sagittal sinus is to carry waste and fluids away from the brain as veins do throughout the rest of the body. It collects blood and other fluid from smaller vessels as it extends from the front to the back of the skull, and it eventually drains that blood and fluid into the internal jugular vein. The internal jugular vein carries most of the blood away from the head, moving the deoxygenated blood back to the heart. From there, it is pumped into the lungs to be reoxygenated and returned to the brain and other parts of the body.
The superior sagittal sinus also has a role in maintaining the balance of cerebrospinal fluid. Small valves that move cerebrospinal fluid into the dural sinuses are located in the walls of the superior sagittal sinus. These valves help recirculate and move fluid, controlling the volume of cerebrospinal fluid in the brain. Too much or too little of this fluid can lead to significant neurological problems.
Learn More: Blood Flow Through the Heart
Clinical Significance
The duct system of the brain is complex, so when problems arise here, they can have a major impact on the entire body. Since blood and other fluids are carried through the superior sagittal sinus and other vessels in the dural venous sinus, blockages caused by clots or malformations can be deadly.
A number of conditions and issues that can affect the superior sagittal sinus include:
Dural arteriovenous fistula: This condition is a rare problem that arises when vessels are connected in an abnormal way. When these misconnections involve the superior sagittal sinus, they can lead to bleeding in the brain (a stroke) or an increase in pressure in the veins of the central nervous system (venous hypertension). These malformations can be treated surgically, in many cases by the placement of a stent.
Blood clots: The superior sagittal sinus is more prone to thrombosis, or clot formation, than other vessels of the dural venous system. The reasons for this include the direction of drainage into the superior sagittal sinus from other vessels and a higher incidence of infectious organisms entering from the veins that drain into the superior sagittal sinus. While clots in the superior sagittal sinus aren't the primary location for most strokes, they can occur here. When clots form in the superior sagittal sinus, intracranial pressure rises, causing focal neurological problems like headaches, paralysis on one side of the body, and seizures. Treatments vary and can involve the use of blood thinners, but these drugs can also increase the risk of strokes as a result of too much bleeding in the brain once the clot is resolved.
Bleeding: Bleeding can occur in the superior sagittal sinus for a number of reasons, from clots to traumatic injury. Bleeding from the superior sagittal sinus can lead to an increase in intracranial pressure, which could result in herniation of brain tissue or restriction of blood flow. It is a medical emergency requiring immediate treatment.
Increased intracranial pressure: Since the superior sagittal sinus moves fluid and cerebrospinal fluid, there is also a risk that malfunction in this vessel can lead to increased intracranial pressure. Increased intracranial pressure is a serious medical issue that requires careful treatment to avoid permanent brain damage.
Tumor: Tumors or growths that can increase intracranial pressure or cause other problems can form on the superior sagittal sinus. Meningiomas are the most common type of tumors found in this section of the brain. These tumors form in the central nervous system and are often benign, but their presence alone is enough to cause symptoms like headaches and seizures. Treatments for meningiomas vary, but surgical removal can be difficult when tumors form here. Recurrences are common if the entire tumor cannot be removed.
Related: Elevated Intracranial Pressure (ICP)
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