[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/) › Sigmoid sinus [Cardiovascular system](https://durgical.com/en/anatomy/system/cardiovascular-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Sigmoid sinus The sigmoid sinus is an S-shaped vein channel behind the ear that becomes the internal jugular vein; ear infections can spread to it. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=sigmoid_sinus&side=r) Opens in the Durgical app, no sign-up needed. ## What it is An S-shaped sinus just behind the mastoid. ## What it does Becomes the internal jugular vein at the jugular foramen; ear infections can spread to it. ## Key points - Curves down in an S-shaped groove on the inner surface of the mastoid part of the temporal bone, separated from the mastoid cells by a thin plate of bone - Mastoiditis or middle-ear infection can cross that plate: sigmoid (lateral) sinus thrombophlebitis with spiking fevers, and raised intracranial pressure (otitic hydrocephalus) - Ends at the jugular foramen, where it continues as the [internal jugular vein](https://durgical.com/en/anatomy/internal-jugular-vein/) through the jugular bulb ## Key facts **Drains** Transverse and superior [petrosal sinuses](https://durgical.com/en/anatomy/superior-petrosal-sinus/) **Into** Internal jugular vein at the jugular foramen ## Relations **Course** From the end of the [transverse sinus](https://durgical.com/en/anatomy/transverse-sinus/) at the petrous [temporal bone](https://durgical.com/en/anatomy/temporal-bone/) it turns down and medially in the groove behind the mastoid, then forward onto the [occipital bone](https://durgical.com/en/anatomy/occipital-bone/) to reach the back of the [jugular foramen](https://durgical.com/en/anatomy/jugular-foramen/) **Lateral** Mastoid cells and the mastoid process; the mastoid emissary vein leaves through the bone to the scalp veins behind the ear **Medial** Cerebellar hemisphere, across the dura **In front** In the jugular foramen, the [glossopharyngeal nerve](https://durgical.com/en/anatomy/glossopharyngeal-nerve/), [vagus nerve](https://durgical.com/en/anatomy/vagus-nerve/) and [accessory nerve](https://durgical.com/en/anatomy/accessory-nerve/) and the inferior petrosal sinus pass in front of it ## How to find it Lies behind the external [ear canal](https://durgical.com/en/anatomy/external-acoustic-meatus/), beneath the mastoid. In mastoid surgery its bluish wall bounds the dissection, and the retrosigmoid approach to the cerebellopontine angle is made just behind it. ## Examination - Griesinger sign: swelling and tenderness over the back of the mastoid from thrombosis of the mastoid emissary vein, pointing to sigmoid sinus thrombosis ## On imaging Contrast CT or MR venography shows thrombosis as a filling defect, sometimes with an empty delta sign; temporal bone CT shows opacified mastoid cells and erosion of the bony plate over the sinus. ## Clinical notes - Otogenic sinus thrombosis can extend into the internal jugular vein and shed septic emboli to the lungs - Abscess beside the sinus (perisinus) and cerebellar abscess are other intracranial complications of mastoiditis - A diverticulum or a gap in the bony wall of the sinus can cause pulsatile tinnitus ## Anatomical variants - A sinus lying unusually far forward, or a high jugular bulb, narrows the working space in ear surgery ## Development It is the lower end of the channel that forms above and behind the developing inner ear to bypass the closed part of the primary head vein; it joins the surviving lower part of that vein, the internal jugular. ## Related conditions - [Cerebral venous sinus thrombosis](https://durgical.com/en/conditions/cerebral-venous-sinus-thrombosis/) ## Test yourself Think of the answer, then tap the question to see it. ## What separates the sigmoid sinus from the mastoid air cells? Only a thin plate of bone, as it curves down in an S-shaped groove on the inner surface of the mastoid part of the temporal bone. ## Which ear infection complication involves the sigmoid sinus, and how does it present? Sigmoid (lateral) sinus thrombophlebitis from mastoiditis or middle-ear infection: spiking fevers and raised intracranial pressure (otitic hydrocephalus). ## What is the Griesinger sign and what does it suggest? Swelling and tenderness over the back of the mastoid from thrombosis of the mastoid emissary vein; it points to sigmoid sinus thrombosis. ## Where does the sigmoid sinus end? At the jugular foramen, where it continues as the internal jugular vein through the jugular bulb. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/sigmoid-sinus/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** sinus sigmoideus TA2 4847 **Official Spanish (DeCS)** Seno sigmoideo DeCS D003392 **English (TA2)** Sigmoid sinus **Also called** sinus sigmoides ## Related - [Transverse sinus](https://durgical.com/en/anatomy/transverse-sinus/) - [Jugular foramen](https://durgical.com/en/anatomy/jugular-foramen/) - [Temporal bones](https://durgical.com/en/anatomy/temporal-bone/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=3408&filter=ths_termall&q=Cranial%20Sinuses); [Neuroanatomy, Dural Venous Sinuses](https://www.ncbi.nlm.nih.gov/books/NBK482257/); Anatomy of the Human Body (20th ed.): Development of the Vascular System (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain. ## **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/sigmoid-sinus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/sigmoid-sinus/