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Anatomy of the posterior fossa emissary veins and their clinical importance Poster No.: C-1752 Congress: ECR 2013 Type: Educational Exhibit Authors: R. Pekcevik, Y. Pekcevik; Izmir/TR Keywords: Computer Applications-Detection, diagnosis, MR-Angiography, CT-High Resolution, CT-Angiography, Head and neck, Congenital DOI: 10.1594/ecr2013/C-1752 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myESR.org Page 1 of 43 Learning objectives 1) To review and simplify the complex anatomy of the posterior fossa emissary veins. 2) To describe their anatomy using high resolution CT, CT angiography and MR venography images. 3) To discuss clinical importance of reporting these vascular variants. Background An emissary (Latin emissarium, from ex and mittere, to send out) is a channel, natural or artificial, by which an outlet is formed to carry off any stagnant body of water (Figure 1). Page 2 of 43 Fig. 1: Ephesus, Izmir, Turkey. The ancient Romans excelled in the construction of emissaries, as in all their hydraulic works. This is the Roman communal bathroom. Water running underneath the toilets and there is a channel in front, that had running water for washing up after. References: - Izmir/TR Mastoid emissary vein (MEV), condylar emissary veins and petrosquamosal sinus (PSS) are valveless veins which pass through cranial apertures. They participate in the extracranial venous drainage of posterior fossa dural sinuses. They protect the brain from increases of the intracranial pressure. Emissary veins also help to cool venous blood circulating through cephalic structures (1,2). They may be associated with inner ear malformations and craniofacial syndromes (1-3). Images for this section: Fig. 1: Ephesus, Izmir, Turkey. The ancient Romans excelled in the construction of emissaries, as in all their hydraulic works. This is the Roman communal bathroom. Water running underneath the toilets and there is a channel in front, that had running water for washing up after. Page 3 of 43 Imaging findings OR Procedure details Embryology The major cerebral venous outflow pathways are the internal jugular veins (IJV) and the vertebral venous system (VVS). Internal jugular vein is dominant in the supine position and transfer of the IJV outflow to the VVS when standing upright (3). External juguler veins (EJV) predominantly drain the viscerocranium and the neurocranium and their participation in the cerebral venous drainage is limited (4). Development of the intracerebral veins and their extracranial drainage is complex in humans. The primary capillary plexus of the early embryo develops in three layers. The superficial vessels drain into the external jugular vein; the middle and deep vessels drain into the internal jugular vein. Emissary veins, in the third trimester, consist of residual connections between the superficial and middle layers (4,5). In humans, the venous drainage of the posterior fossa has frequent anatomical variations. Most variations involving the lateral sinus in humans allow conservation of the IJV and VVS as their major outflow pathways. Only rarely, when the sigmoid sinus is absent or severely hypoplastic, may a petrosquamosal sinus, mastoid emissary or posterior condylar emissary vein represent the major or only drainage pathway of the transverse sinus (4, 6). Anatomy Mastoid emissary vein Mastoid emissary vein crosses the mastoid foramen (Figure 2) and runs between sigmoid sinus and the posterior auricular or the occipital vein. The the posterior auricular and the occipital vein drains into suboccipital venous plexus or internal jugular vein (Figure 3-5). The suboccipital venous plexus is located above the splenius capitis muscle and pass through a cleft between the semispinalis and longissimus capitis muscle and drains anterior vertebral vein or deep cervical vein (3, 7). (Figure 6) Page 4 of 43 Fig. 2: Mastoid foramina. 3D VR, CTA posterior view show one foramen on the left, two foramina on the right side. References: - Izmir/TR Page 5 of 43 Fig. 3: Oblique MPR CTA images show mastoid emissary canal and vein (long arrow) that runs between sigmoid sinus (S) and the posterior auricular vein (double arrows)and then suboccipital venous plexus (white arrow). References: - Izmir/TR Page 6 of 43 Fig. 4: 3D VR CTA lateral view show the mastoid emissary foramen and vein (black arrow) that drain into posterior auricular vein (double arrows) and then suboccipital venous plexus (white arrow). References: - Izmir/TR Page 7 of 43 Fig. 5: 3D VR CTA posterior view show the mastoid emissary foramen and vein (black arrow) that drain into posterior auricular vein (double arrows) and then suboccipital venous plexus (white arrow). Occiptal vein (arrowhead). References: - Izmir/TR Page 8 of 43 Fig. 6: 3D PCA MR venography shows the suboccipital venous plexus that is located above the splenius capitis muscle (rectangular), pass through a cleft between the Page 9 of 43 semispinalis (ellipse) and longissimus (trianguler) capitis muscle and drains into deep cervical vein (arrow). References: - Izmir/TR Emissary condylar veins Emissary condylar veins are divided into three groups as posterior, lateral and anterior condylar veins (3,7). The posterior condylar vein usually took its origin from the superior bulb of the internal jugular vein. It courses along the posterior condylar vein canal, emerges from its foramen (Figure 7) and drains into the deep cervical vein. It has connection with the horizontal portion of the vertebral artery venous plexus (Figure 8-10). The lateral condylar vein generally orginates from a venous network near internal juguler vein and then drains into vertebral venous system (Figure 15). The anterior condylar vein appeared as a plexiform connection of the anterior internal vertebral venous plexus with the internal jugular vein. Fig. 7: 3D VR CTA posterior view show bilateral condylar foramen (arrows). References: - Izmir/TR Page 10 of 43 Fig. 8: Axial MPR CTA images show posterior condylar emissary canal and vein (arrows. References: - Izmir/TR Page 11 of 43 Fig. 9: Ssagittal oblique MPR CTA images show posterior condylar emissary canal and vein (arrows). References: - Izmir/TR Page 12 of 43 Fig. 10: 3D VR CTA lateral oblique view show the posterior condylar emissary foramen (arrowhead). Posterior condylar vein drain into the deep cervical vein (arrows) and vertebral plexus around the horizontal portion of the vertebral artery (double arrows). References: - Izmir/TR Occipiatal emissary vein Occipital emissary vein connects the transvers sinuses near the confluens sinuum region to the suboccipital plexus (3, 7) (Figure 11,12). Page 13 of 43 Fig. 11: 3D VR CTA posterior view shows occipital emissary vein foramina (arrows). References: - Izmir/TR Page 14 of 43 Fig. 12: Sagittal MPR CTA images (the same patient as in Fig. 11) shows occipital emissary vein canal and vein (arrows)that connects the confluens sinuum to the occipital vein. References: - Izmir/TR Petrosquamosal sinus Petrosquamosal sinus (PSS) arises from the transverse sinus before its confluence with the superior petrosal sinus and drains either into the retromandibular vein through the postglenoid foramen (PGF) or into the pterygoid venous plexus through the foramen ovale (4, 5). The external jugular vein (EJV) is the main drainage pathway of the PSS (Figure 13-15). Page 15 of 43 Fig. 13: Axial HRCT image shows a sulcus (white arrow), originating from the anterior portion of the transverse sinus and passing anteriorly through the lateral portion of the petrous bone. References: - Izmir/TR Page 16 of 43 Fig. 14: Sagittal reformatted CT image shows the PSS ending in the postglenoid foramen (white arrow). The black arrow indicates is mastoid emissary canal. References: - Izmir/TR Page 17 of 43 Fig. 15: 3D PCA MRV, right posterolateral oblique MIP image shows the right mastoid emissary vein (arrow) draining into large occipital vein, suboccipital venous plexus and then deep cervical vein. Posterior condylar vein (double arrows), ascends from the superior bulb of the internal jugular vein to the deep cervical vein. Lateral condylar vein (small arrowhead) takes its origin from internal juguler vein and connected with the vertebral artery venous plexus. Large arrowhead shows the petrosquamosal sinus, (the same patient as in Fig. 8). References: - Izmir/TR Clinical significance Page 18 of 43 Diagnosis and describing PSS, MEV and other emmissary veins is very important because: -Emissary veins are associated with inner ear malformations and syndromic craniosynostosis (1,6,9) -They are potential source of intense bleeding and air or surgical material embolism during surgical procedures (2,3,7). -They can be the source of thrombosis in the sigmoid sinus occurring after middle ear surgery or of a retrograde, thrombophlebitic extension from an infected mastoid cavity (5,10). - Emissary veins can become may represent the main outflow pathway of the transverse sinus in some cases. Particular care should be taken during surgical procedures, as the sacrifice of this outflow pathway could lead to catastrophic venous ischemic and hemorrhagic consequences (1,3) (Figure 16). Page 19 of 43 Page 20 of 43 Fig. 16: Mastoid emissary vein is originating from sigmoid sinus (S) and draining into the external jugular vein. References: - Izmir/TR - They may be enlarged due to jugular vein trombosis and mentioning this preoperatively may change the surgical approach (Figure 17) Page 21 of 43 Page 22 of 43 Fig. 17: 3D VR CTA posterior view shows enlarged posterior condylar vein, deep cervical vein and vertebral venous plexus due to right jugular vein trombosis (arrows). References: - Izmir/TR -They may have close relationship with the skull base or neck tumors (Figure 18) Page 23 of 43 Fig. 18: Sagittal MIP CTA shows hypervascular neck lesion that has close relationship with posterior condylar vein (arrow). References: - Izmir/TR -The diameter of the MEV may be important that this vessel could be a potential target for cannulation during endovascular procedures involving the transverse or sigmoid sinus (3,12). Endovascular treatment of dural arteriovenous fistulas can be done via large mastoid emissary vein(7). Images for this section: Fig. 2: Mastoid foramina. 3D VR, CTA posterior view show one foramen on the left, two foramina on the right side. Page 24 of 43 Fig. 3: Oblique MPR CTA images show mastoid emissary canal and vein (long arrow) that runs between sigmoid sinus (S) and the posterior auricular vein (double arrows)and then suboccipital venous plexus (white arrow). Page 25 of 43 Fig. 4: 3D VR CTA lateral view show the mastoid emissary foramen and vein (black arrow) that drain into posterior auricular vein (double arrows) and then suboccipital venous plexus (white arrow). Page 26 of 43 Fig. 5: 3D VR CTA posterior view show the mastoid emissary foramen and vein (black arrow) that drain into posterior auricular vein (double arrows) and then suboccipital venous plexus (white arrow). Occiptal vein (arrowhead). Page 27 of 43 Fig. 6: 3D PCA MR venography shows the suboccipital venous plexus that is located above the splenius capitis muscle (rectangular), pass through a cleft between the Page 28 of 43 semispinalis (ellipse) and longissimus (trianguler) capitis muscle and drains into deep cervical vein (arrow). Fig. 7: 3D VR CTA posterior view show bilateral condylar foramen (arrows). Page 29 of 43 Fig. 8: Axial MPR CTA images show posterior condylar emissary canal and vein (arrows. Page 30 of 43 Fig. 9: Ssagittal oblique MPR CTA images show posterior condylar emissary canal and vein (arrows). Page 31 of 43 Fig. 10: 3D VR CTA lateral oblique view show the posterior condylar emissary foramen (arrowhead). Posterior condylar vein drain into the deep cervical vein (arrows) and vertebral plexus around the horizontal portion of the vertebral artery (double arrows). Page 32 of 43 Fig. 11: 3D VR CTA posterior view shows occipital emissary vein foramina (arrows). Page 33 of 43 Fig. 12: Sagittal MPR CTA images (the same patient as in Fig. 11) shows occipital emissary vein canal and vein (arrows)that connects the confluens sinuum to the occipital vein. Page 34 of 43 Fig. 13: Axial HRCT image shows a sulcus (white arrow), originating from the anterior portion of the transverse sinus and passing anteriorly through the lateral portion of the petrous bone. Page 35 of 43 Fig. 14: Sagittal reformatted CT image shows the PSS ending in the postglenoid foramen (white arrow). The black arrow indicates is mastoid emissary canal. Page 36 of 43 Fig. 15: 3D PCA MRV, right posterolateral oblique MIP image shows the right mastoid emissary vein (arrow) draining into large occipital vein, suboccipital venous plexus and then deep cervical vein. Posterior condylar vein (double arrows), ascends from the superior bulb of the internal jugular vein to the deep cervical vein. Lateral condylar vein (small arrowhead) takes its origin from internal juguler vein and connected with the vertebral artery venous plexus. Large arrowhead shows the petrosquamosal sinus, (the same patient as in Fig. 8). Page 37 of 43 Page 38 of 43 Fig. 16: Mastoid emissary vein is originating from sigmoid sinus (S) and draining into the external jugular vein. Page 39 of 43 Page 40 of 43 Fig. 17: 3D VR CTA posterior view shows enlarged posterior condylar vein, deep cervical vein and vertebral venous plexus due to right jugular vein trombosis (arrows). Fig. 18: Sagittal MIP CTA shows hypervascular neck lesion that has close relationship with posterior condylar vein (arrow). Page 41 of 43 Conclusion We believe that posterior fossa emissary veins can be detected by radiologist before surgery with thorough understanding of their anatomy. 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