Dural Venous Sinuses Flashcards
Functions of the meninges
Separate soft tissue of brain from cranium
Protect blood vessels that supply brain
Contain and circulate CSF
Parts of the meninges form some veins that drain blood from brain
Draw the layers of the meninges
Refer to drawings
Meningeal and Periosteal layers
Meningeal layer is usually fused with periosteal layers, except in areas where two layers separate to from large blood filled spaces called the dural venous sinuses
Draw the layers of the dura including the dural venous sinus, emissary and bridging veins
Refer to drawings
How are dural venous sinuses different from veins?
Dural sinuses are more like spaces that contain venous blood.
Emissary v.
Bridging v.
- drains blood from the scalp to the dural venous sinus
- drains blood from the cerebral cortex to the dural venous sinus
Arachnoid mater properties
Partially composed of web of collagen elastic fibers (arachnoid trabeculae)
Space between the dura and arachnoid is the subdural space/potential space (not normally there, unless something is wrong)
Deep to the arachnoid is the subarachnoid space
Potential causes of existence of subdural space between the dura and arachnoid mater?
- bleeding from the bridging v.
- following a lumbar puncture, CSF is taken from the subarachnoid space , creating negative pressure and creating the separation
Are there arteries in the subarachnoid space?
Yes. Aneurysms in these cerebral arteries can rupture and cause bleeding in the subarachnoid space (main causes are artery wall weakening or hypertension)
Describe the formation of the cranial dural septa and its function
Meningeal layer extends downward to form an opening, called the cranial dural septa. This is basically a membrane that separates the hemispheres of the brain
Function is to help stabilize and support the entire brain
Four important septa:
Falx cerebri
Tentorium Cerebelli
Falx cerebelli
Diahragma sellae
Draw the four cranial dural septa
Refer to drawings
What does each septum separate?
Falx cerebri - two halves of the cerebrum
Falx cerebelli - two halves of the cerebellum
Tentorium cerebelli - cerebrum from cerebellum
Diaphragma sellae - forms the roof of the pituitary fossa
Draw the arterial supply to the meninges:
Refer to drawings
What is the main blood supply to the meninges?
What foramen does it pass through?
Middle meningeal artery
Foramen spinosum
Draw the innervation of the meninges
Refer to drawings
Middle meningeal a. rupture
Artery courses between the skull and the dura mater. Rupture causes bleeding between the skull and the dura (epidural space), causing epidural hematoma
Where are you most likely to get an epidural hematoma?
Pterion, junction of the temporal, parietal and occipital bone. Suture junction makes it a weaker spot and skull here is thinner. Anterior branch of the middle meningeal a. is right at the pterion, so trauma here is more susceptible to artery rupture
Bridging vein rupture
Subdural hemorrhage, bleeding creates a potential space between the dura and arachnoid.
Common in elderly who suffer acceleration/deceleration injury or Shaken baby syndrome
Aneurysm rupture
-Blood vessels in the subarachnoid space can form aneurysms and rupture causes bleeding into the subarachnoid space.
-Can also happen after a lumbar puncture
Clinically: severe headache (worst headache of life), vomiting, photophobia
Sigmoid sinus drains down and becomes the …
Internal jugular v.
Significance of the superior ophthalmic, inferior ophthalmic and facial veins?
Located on the face and connected to the cavernous sinus. Infection in the face can spread to the cavernous sinus
Significance of the superior and inferior petrosal sinuses:
Thecavernous sinus drainsby these two channels ultimately into the internal jugular vein via the sigmoidsinus
Where is the cavernous sinus located?
Paired cavities that side on either side of the sphenoid bone, drains venous blood from the vein to the internal jugular v.
What are the contents of the Cavernous sinus?
Vessels: internal Carotid A.
Nerves: CN III, IV, VI, V1, V2
Draw the Path of the Internal carotid artery as it enters the brain and branches into the cerebral arteries
Refer to drawings
Cavernous Sinus thrombosis
Since there are a lot of cranial nerves in the cavernous sinus, infection in this area (or in the face, where the veins are connected to the cavernous sinus) can lead to various symptoms depending on the affected nerves
Clinical: high fever, periorbital edema and chemosis, cranial nerve palsies (most commonly CN VI), decreased visual acuity
Functions of CSF:
- buoyancy
- protection
- environmental stability
How is the CSF formed?
Choroid plexus (blood vessels) in the ventricle. Ependymal cells here secrete fluid from their blood plasma. Fluid flows from the choroid plexus and around the brain Composition is more Na+, H+ and Ca2+, less potassium
Describe the drainage of the CSF?
Drains via the arachnoid granulation > to the Dural venous sinuses > internal jugular v.
-drainage system prevents clogging of the CSF in the brain
Subarachnoid hemorrhage and Arachnoid granulations:
Arachnoid granulations can be damaged by blood as it mixes with the CSF. The granulations fibrose and limits their ability to drain the CSF properly.
Hydrocephalus
Ineffective drainage of the CSF causes clogging in the brain, causing compression and shrinkage of the brain and enlargement of the ventricles.
Clinically presents as enlarged head
