[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Confluence of sinuses [Cardiovascular system](https://durgical.com/en/anatomy/system/cardiovascular-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Confluence of sinuses The confluence of sinuses, at the back of the skull, is where the main vein channels draining the brain meet before flowing to each side. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=confluence_of_sinuses&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The meeting point of the dural sinuses at the back of the head. ## What it does Where the superior sagittal, straight and transverse sinuses join. ## Key points - Lies against the internal occipital protuberance, opposite the external occipital protuberance (inion), where the falx cerebri, tentorium cerebelli and falx cerebelli meet - Rarely a symmetric crossroads: the superior sagittal sinus often turns mainly into the right [transverse sinus](https://durgical.com/en/anatomy/transverse-sinus/) and the straight sinus into the left, or a septum splits the confluence - Its position helps read fetal and infant imaging: high in Dandy–Walker malformation (raised tentorium), low in Chiari II malformation with a small posterior fossa - Clot or injury here can block drainage from several sinuses at once, so intracranial pressure can rise quickly ## Key facts **Drains** Superior sagittal and straight sinuses (and the occipital sinus) **Into** Both transverse sinuses (the right usually larger) ## Relations **Above** Occipital lobes either side of the [falx cerebri](https://durgical.com/en/anatomy/falx-cerebri/); the [superior sagittal sinus](https://durgical.com/en/anatomy/superior-sagittal-sinus/) enters from above **Below** Cerebellar hemispheres either side of the falx cerebelli; the occipital sinus enters from below **In front** [Straight sinus](https://durgical.com/en/anatomy/straight-sinus/), arriving along the junction of the falx cerebri and [tentorium](https://durgical.com/en/anatomy/tentorium-cerebelli/) with the deep venous blood of the great cerebral vein **Lateral** Transverse sinuses leaving on both sides in the attached edge of the tentorium, toward the [sigmoid sinus](https://durgical.com/en/anatomy/sigmoid-sinus/) and [internal jugular vein](https://durgical.com/en/anatomy/internal-jugular-vein/) **Behind** Inner surface of the [occipital bone](https://durgical.com/en/anatomy/occipital-bone/) at the internal occipital protuberance ## How to find it The external occipital protuberance (inion) is felt as the bony bump in the midline at the back of the head; the confluence lies just deep to it. Burr holes and suboccipital approaches are planned to stay clear of this point. ## On imaging CT or MR venography shows the confluence and whether both transverse sinuses fill; thrombosis gives a filling defect or an empty delta sign here. Normal arachnoid granulations and slow flow in a non-dominant transverse sinus can mimic clot. ## Clinical notes - Depressed occipital fractures over the confluence are handled cautiously, because lifting the fragment can tear the sinuses and cause major bleeding - Venous sinus thrombosis reaching the confluence impairs drainage of both hemispheres: headache, papilloedema, seizures and venous infarcts - Meningiomas near the confluence are planned around which sinuses are dominant and still open, since sacrificing a dominant one can cause venous infarction ## Anatomical variants - Drainage patterns vary: symmetric, right-dominant (the commonest), split into two channels, or with one transverse sinus hypoplastic - The occipital sinus can be large in infants and may drain directly toward the sigmoid sinus or the vertebral venous plexus ## Memory aid Its old name, torcular Herophili, means the wine press of Herophilus: the place where the streams of venous blood are squeezed together. ## Test yourself Think of the answer, then tap the question to see it. ## Which surface landmark marks the confluence of sinuses? The external occipital protuberance (inion): the confluence lies just deep to it, against the internal occipital protuberance. ## Which sinuses join at the confluence of sinuses? The superior sagittal and straight sinuses (and the occipital sinus) drain in, and both transverse sinuses leave it, the right usually larger. ## Why is a depressed occipital fracture over the confluence of sinuses handled cautiously? Lifting the fragment can tear the sinuses and cause major bleeding. ## How does the position of the confluence of sinuses differ in Dandy–Walker malformation and Chiari II malformation? It is high in Dandy–Walker malformation (raised tentorium) and low in Chiari II malformation, with a small posterior fossa. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/confluence-of-sinuses/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** confluens sinuum TA2 4852 **Official Spanish (DeCS)** Confluencia de los senos **English (TA2)** Confluence of sinuses **Also called** torcular of Herophilus Sources: Terminologia Anatomica (TA2); [Neuroanatomy, Dural Venous Sinuses](https://www.ncbi.nlm.nih.gov/books/NBK482257/); [Neuroanatomy, Superior Sagittal Sinus](https://www.ncbi.nlm.nih.gov/books/NBK546615/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/confluence-of-sinuses/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/confluence-of-sinuses/