Sigmoid Sinus: Structure, Function & Diseases

The sigmoid sinus is a blood pathway in the brain. It runs in a s-shaped manner and transports venous blood. It provides blood supply to the brain.

What is the sigmoid sinus?

In the human brain, there are a number of vessels that serve to ensure blood supply to the brain. The sigmoid sinus is a central blood vessel located in the back of the head. The posterior cranial vein is called the occipital vein and forms the entire posterior region of the head. What makes the venous conductor special is its shape. In a cross-section of the brain, it can be clearly seen that it takes on an s-shaped form. Many different branches originate from it, which supply blood in deeper tissue layers. Venous blood flows in the sigmoid sinus. The vessel wall is thin-skinned. This makes it well suited for the external delivery of drugs and other messenger substances, but it is also more susceptible to damage. The transport of messengers and nutrients in the sigmoid sinus is very rapid. This means that substances in the blood can be transported to their site of action via this blood conductor in a matter of seconds or minutes. In addition, the sigmoid sinus serves as the main evacuation route for venous blood from the brain.

Anatomy and structure

The dura mater, the hard meninges that protectively surround the brain, forms duplications. This process creates cavities in the meninges. These are used by venous blood conduits to provide blood supply within the brain. Blood from the meninges, brain area and orbit is collected in the cavities. It then flows into the internal jugular vein. This is located in the posterior fossa of the skull, the foramen jugulare. The superior sagittal sinus is located there. This runs along the upper edge of the falx cerebri. The inferior sagittal sinus runs along the lower border and ends in the rectus sinus. Subsequently, the superior sagittal sinus and the inferior sagittal sinus merge. From the confluens, the path continues as the transverse sinus. This frames the posterior fossa laterally and posteriorly. Ventrally, it continues and merges into the sigmoid sinus, which curves in an s-shape. The sigmoid sinus terminates in the jugular foramen. This is the site of origin of the internal jugular vein.

Function and Tasks

Important messenger substances are transported via the blood. These are vital for the supply of organs and vessels. They include, for example, cells, hormones or protein-containing blood plasma. The blood thus plays a central role in transport. Via the veins and arteries, the various active substances are transported to and from the organs. The sigmoid sinus is an essential component in this system of many vascular branches. It is responsible for a wide area in the back of the skull. Through its activity, the supply of the brain is essentially ensured. In addition, it is responsible for the removal of cerebral blood. This means, for example, that hormones produced in the pituitary gland or the posterior pituitary lobe can be quickly transported out of the brain through the sigmoid sinus and reach the organs where they are to exert their effect. Heat regulation also takes place via the blood. This ensures the correct temperature in the brain via the sigmoid sinus. During surgical interventions in the head region, the sigmoid sinus often serves as an access route. Because of its location and size, it can be used by surgeons to navigate a path through the skull wall to the cerebellopontine angle. The sigmoid sinus supplies the superior veins inside the skull. Because of its shape, it offers many opportunities for branching.

Diseases

Inflammation is considered a common disease of blood vessels throughout the human body. In this disease, a blood clot forms within a blood vessel. The sigmoid sinus is highly susceptible to sinus vein thrombosis. This can be triggered by suppuration of the middle ear. This is not initially noticed by the patient. If it continues to grow, congestion of the blood and initial complaints occur. These manifest themselves as pain in the affected region as well as feelings of tension. Even though sinus vein thrombosis is rare, there is a risk of dying from a stroke due to the clot. Most patients are between the ages of 30 and 40.In addition, the clot can dislodge and be transported to the heart. From there, it follows the flow to the lungs. If the clot, which is also known as a thrombus, blocks a blood vessel at this point, the patient suffers a pulmonary embolism. This is classified as life-threatening. The vascular walls of veins in the human body are thin. This leaves them vulnerable to lesions. Once the sigmoid sinus is damaged, problems arise in supplying the brain one. In addition, the removal of venous blood from the brain is no longer guaranteed. Veins are assigned a central role in diseases such as cancer. Cancer cells are transported in them to any place in the body. As soon as they detach from a formed tumor, they enter the bloodstream. Regardless of where they are transported off to, the cancer cells can form new metastases at this site. Thus, new tumors are formed and the disease continues to spread unintentionally.