Sigmoid Sinus

**Sigmoid sinus** is an unpaired venous sinus located on the anterior surface of the body along the internal carotid artery and on the lateral surface of the temporal bone. Starting in the area of ​​the angle and greater wing of the sphenoid bone, it runs along the outer surface of the petrous part of the temporal bone and enters the cavernous sinus. In this case, venous blood from the sigmoid sinus enters the venous bed of the neck through the glossocarpal foramen and the internal jugular vein. When connected to the cavernous sinus, it is its superior continuation. The length of the sigmoid sinus reaches 30-40 mm, the diameter is 0.3-0.5 cm. The formation of its mucous membrane involves the inner layers of the internal carotid arteriovenous membrane, the outer layer of which (to the internal and external carotid arteries and the basilar region) passes into the mucosa shell of the sphenoparietal cranial fossa. Cavernous transformation, which is predisposed by an increase in pressure in the area of ​​the superior vena cava (up to 60 mm Hg), often occurs in children under the age of 9 years. Inflammatory processes in the cavity of the skull, nose, and middle ear are manifested by thrombosis of the sigmoid sinus, which can lead to its perforation. In these cases, along with blood, pus enters the subarachnoid space of the pericardium, onto the surface of the spinal cord, and into the ventricles of the brain, which is one of the causes of meningitis.