Venous Sinuses PDF

The Venous System Prof Dara M Cannon The Venous System • Veins drain intracranial and extracranial regions • Extracranial venous system to sinuses via the ‘emissary’ vessels crossing skull • Uncommon but potential route for infection • Intracranial veins are • superficial, • deep or • dural in ty...

The Venous System Prof Dara M Cannon The Venous System • Veins drain intracranial and extracranial regions • Extracranial venous system to sinuses via the ‘emissary’ vessels crossing skull • Uncommon but potential route for infection • Intracranial veins are • superficial, • deep or • dural in type and drain to the internal jugular bulb and vein Intracranial Venous Drainage • Superficial drainage • Superficial cerebral veins, to superior sagittal sinus • Deep Drainage • Internal cerebral veins, bilateral, formed by the union of the posterior and anterior terminal veins • Great cerebral vein (of Galen), union of the internal cerebral veins, Most common location for malformation in infants and foetuses, drains to the straight venous sinus • Venous Sinuses • A series of large veins that reside between the dural sublayers and ultimately drain blood to the Internal jugular vein • Recall CSF drained into these via the arachnoid granulations as the end of the CSF route where it then merges with venous blood Venous Sinuses • Venous sinuses are large vessels the reside between the periosteal and meningeal sub layers of the dura mater • They contain and transport venous blood Dura • Are endothelial lined spaces • Large veins from the surface of the brain and diploe empty into them • Ultimately drain to the internal jugular veins Dura • CSF arrives into them as well via the arachnoid granulations Objectives • To describe and be able to identify the main systems for drainage of deoxygenated blood from the brain and the route and relations of the venous sinus system to the meninges The Superior Sagittal Sinus • Runs along the superior border of the falx cerebri • Begins at the crista gali of the ethmoid bone • Ends near the internal occipital protuberance, at the confluence of the sinuses The Inferior Sagittal & Straight Sinuses • The inferior sagittal sinus is smaller and shorter than the superior, it runs inside the inferior boarder of the falx cerebri • It drains into the straight sinus which runs along the midline joint between the falx cerebri and the tentorium cerebelli to drain into the confluence of the sinuses The Confluence of the Sinuses & The Transverse Sinus • The superior sagittal and straight sinuses therefore drain into the confluence of the sinuses at the internal occipital protuberance • Blood leaves the confluence to travel laterally in both directions in the transverse sinuses which run in the posterior margin of the tentorium cerebelli • The transverse sinuses along with a network of other smaller venous sinuses (sphenoidal, clival) drain to the sigmoid sinus which ultimately drains to the internal jugular bulb and vein located at the jugular foramen and returning blood to the heart Tracing the route of venous drainage through the venous sinuses noting their relationship to each fold of dura Falcotentorial Apex • Fold of Dura • • • • Falx cerebri Tentorium cerebelli Falx cerebelli Diaphragma sellae • Dural Venous Sinus • • • • • • Superior Sagittal Inferior Sagittal Straight Confluence Tranverse Sigmoid Posterior Brainstem Venogram showing Venous Sinuses Superficial Veins VENOUS SYSTEM – KEYNOTES Veins drain intracranial and extracranial regions Intracranial veins are superficial, deep or dural in type and drain to the internal jugular bulb and vein Notable landmarks to revise or learn before starting include the folds of the dura (falx cerebri, falx cerebelli and the tentorium cerebelli), the cavernous sinus (relation to the carotid artery, cranial nerves and sphenoid bone), the clivus of the skull base, the quadrigemminal cistern and the internal occipital protuberance. DEFINITIONS & COMPARISONS ➢ Dural sinuses are large endothelial-lined trabeculated venous channels encased within the folds or reflections of dura that define and form their walls ➢ Dural venous sinuses communicate with extracranial veins directly via diploic veins in calvarium, emissary veins through basilar foramina ➢ Dural venous sinuses receive blood from superficial (cortical) veins and deep (subependymal) veins ➢ Cerebral veins are thin-walled, valve-less structures that cross SA space, pierce arachnoid dura to enter the dural venous system ➢ Superficial cerebral (cortical) veins lie in the SA space and mainly follow sulci ➢ Deep cerebral (subependymal) veins outline the ventricles • Frontal cortical veins: drain to the superior sagittal sinus • Vein of Trolard = superior anastomotic vein: drains to the vein of Labbe at the posterior rami of the lateral or sylvian fissure (check position with IMAGE) • Superficial middle cerebral vein: drain anteroposteriorly along the lateral or sylvian fissure to join the vein of Labbe along with the vein of trolard • Vein of Labbe = inferior anastomotic vein: drains to the transverse sinus • Inferior superficial veins: drain to the vein of rosenthal (next section) Dural Venous Sinuses • • Superior sagittal sinus: runs anterior to posterior in the superior portion of the falx cerebri along the longitudinal interhemispheric fissure Inferior sagittal sinus: runs in the inferior free margin of the falx cerebri, superior to the corpus callosum Deep Veins • Internal cerebral veins: form from the union of septal and thalamostriate veins • Subependymal veins: outline the lateral and third ventricles • Basal vein of Rosenthal: encircles midbrain • Falcotentorial apex: uppermost and anterior apex of the dural fold, tentorium cerebelli (dividing the supra- and infra-tentorial spaces) • Great vein of Galen: formed from the union of the internal cerebral veins and the vein of Rosenthal, it is a short U shaped vein with a substantially more significant role before birth, it drains to the straight sinus (along with the inferior sagittal sinus) at the falcotentorial apex • Straight sinus: runs from the apex of the tentorium cerebelli to the confluence, superior and anterior to the internal occipital protuberance of the calvarium • Cavum veli interpositi: space within double-layered tela choroidea of the third ventricle, communicates with quadrigemminal cistern • Confluence of the sinuses / Torcular Herophili: formed from the union of the straight and superior sagittal sinuses • Anterior and two lateral pontomesencephalic veins: receives pontine branches, drains to medulla level as the anterior medullary plexus and continues to spinal cord • Transverse sinus: drain horizontally bilaterally to sigmoid sinus • Petrosal vein • Sphenoparietal sinus: arises along the border between the anterior and middle cranial fossa and drains to cavernous sinus • Superior and inferior vermian veins: drain superior and inferior portions of the vermis of the cerebellum • Cavernous sinus: trabeculated venous sinus space containing CNVI and the internal carotid artery (and further CNs in the wall) and possess two (anterior and posterior) intracavernous sinuses communicating between the right and left cavernous sinus spaces either side of the sella turcica in the sphenoid bone. • Tonsillar vein: drains the tonsil of the cerebellum • Sometimes categorized as galenic (superior, drain to galen), petrosal (anterior, drain petrosal area) and tentorial (posterior). Posterior Fossa Veins • Superior petrosal sinus: drain from the cavernous sinus to the transverse sinus • Inferior petrosal sinus: drains from the cavernous sinus to join the jugular bulb with the sigmoidal sinus • Clival venous plexus: drains from the cavernous sinus in a plexus down the clival surface of the skull base toward the foramen magnum • Sigmoid sinus: sigmoid course draining from transverse sinus to the internal jugular bulb and vein • Internal jugular bulb and vein: at jugular foramen, bulb turbulent = pseudo occlusion Summary of Territories • Sphenoparietal sinus drains posterolateral orbital and anterior temporal cortices • Veins of Labbe drain posterior temporal and anterior occipital • Superficial (cortical) veins drain other frontal, parietal, temporal and occipital cortices • Internal and deep cerebral veins drain a central ovoid around the lateral and third ventricles Extracranial Veins • These drain the face, orbits of the eye, scalp, skull (diploic) and neck regions into the anterior and external jugular veins