Meningeal Layers, Duralfolds And Dural Venous Sinuses Flashcards
What are the 3 meningeal layers surrounding the brain and the spinal cord from the most superficial to deep?
How do you remember this order?
Dura mater
Arachnoid mater
Pia mater
DAP
What are the dips in the brain called?
Sulci
What are the bulges of the brain called?
Gyri
What is the Pia mater and how does it run in relation to the brain and the spinal cord?
Microscopic layer that cant be separated from the surface of the brain or spinal cord
It runs in the grooves of the gyri, sulci and the fissures of the brain
How does the arachnoid mater run around the brain and spinal cord?
How does it relate to the Pia mater?
Completely surrounds them but does not run through the gyri, sulci or fissures
Gap between Pia mater and the arachnoid mater
What is the area between the Pia mater and the Arachnoid mater called?
Subarachnoid space
What is contained in the subarachnoid space?
Cerebral arteries and veins (drain into dural venous sinuses)
How does the dura mater run around the brain and the spinal cord?
Outermost layer
In contact with the arachnoid mater due to the arachnoid mater being pushed outwards from the pressure of the CSF in the sub arachnoid space
What is the longitudinal fissure of the brain?
Fissure separating the left hemisphere from the right hemisphere
What are the fissures called that run in the horizontal plan in each hemisphere?
Lateral fissures
Describe the appearance of the Dura mater:
Outermost tough fibrous membrane
Describe the appearance of the Arachnoid mater:
Soft, fibrous translucent membrane
Describe the appearance of the Pia mater:
Delicate and adheres to the surface of the brain following every fold
What are the leptomeninges?
Pia mater + Arachnoid mater
What is meningitis?
How is it normally diagnosed?
Infection of the leptomeninges
Lumbar puncture performed to see if CSF is cloudy
What are the 2 parts of the Dura mater called?
Periosteal dural layer
Meningeal dural layer
What key artery runs between the periosteal layer of dura mater and the inner table of the bones of the skull?
Middle meningeal artery
What is the periosteal layer of Dura mater in contact with?
What is the meningeal layer of dura mater in contact with?
Periosteal layer = inner table of bone of skull
Meningeal = arachnoid mater
Why does the dura mater only have 2 layers in the skull and not the spinal cord?
No periosteal layer adhered to the inner table of bone in the spinal cord since there isn’t any skull bones here
What 2 things can form as a result of the separation of the periosteal layer of dura and the meningeal layer of dura?
Dural venous sinuses
Dural folds
What is a dural venous sinus?
Spaces which fill with venous blood in the skull which then drain to the base of the skull
What layer of dura actually moves outward and forms the dural folds or dural venous sinuses?
Meningeal layer of dura
What is the main dural fold produced by the meningeal layer of dura separating at the skull cap?
Dural fold forming the longitudinal fissure
What is a special dural venous sinus formed at the floor of the cranium?
Why is it special?
Cavernous venous sinus
Contains venous blood but also other important structures
Is a paired dural venous sinus
What is the name of the dural fold which runs all the way along the midline of the skull separating the 2 hemispheres?
Falx cerebri
What is the name of the dural fold which runs in a horizontal plane?
Tentorium cerebelli
What dural fold does the falx cerebri attatch to posteriorly?
The tentorium cerebelli
What does the falx cerebri attach to anteriorly?
Anterior cranial fossa where crista Gali found
What is the tentorial notch?
Opening in the tenntorium cerebelli which allows brainstem to connect to spinal cord
Loo at slide 10 in lecture to look at the different dural venous sinuses
Why are the brains dural folds good?
Helps stabilise the brain acting as rigid dividers portioning the brain
What is the risk of having dural folds in the brain?
Since they’re rigid a rise in pressure in the skull (haemorrhage) can lead to compression and herniation of parts of the brain against the fold and/or through the foramen magnum
What do dural venous sinuses receive blood from?
Each other (connected to each other)
Cerebral veins
What blood vessel do dural venous sinuses drain into?
Internal Jugular Vein
Exit through base of skull as the IJV
Look at the last slide:
What are all of the dural venous sinuses?
1 = superior Sagittal sinus
2 = inferior Sagittal sinus
3 = confluence of sinuses
4 = straight sinus
5 = transverse sinus
6 = sigmoid sinus
7 = cavernous sinus
8 = superior petrosal sinus
9 = inferior petrosal sinus
10 = internal jugular veins
Where is the superior Sagittal sinus located?
Where meningeal layer pulls away treating a gap making the falx cerebri dural fold at the top
Where is the inferior Sagittal sinus?
Inferior margin of falx cerebri
Where is the straight sinus?
What does it connect?
Sits at the junction between the falx cerebri and the tentroium cerebelli
It connects the inferior Sagittal sinus to the superior Sagittal sinus via the confluence of sinuses
What other 2 sinuses span laterally from the confluence of sinuses?
Left and right Transverse sinuses
What sinus leads from the transverse sinuses?
What do these sinuses lead to?
Sigmoid sinuses
Leads to the jugular Foramen wher the venous blood drains through the base of the skull via the internal jugular vein
Where is the cavernous sinus found and describe its structure?
2 dural venous sinuses found on the middle of the cranial fossa near the body of the sphenoid
Communicates with other sinuses
What sinuses does the cavernous sinus communicate with?
Sigmoid sinus
Transverse sinus
How does the cavernous sinus communicate with the transverse sinus?
Superior petrosal sinus
How does the cavernous sinus communicate with the sigmoid sinus?
Inferior petrosal sinus
What are the 2 important venous connections between the venous sinuses and other venous structures?
Bridging veins
Emissary veins
What blood vessels do bridging veins connect dural venous sinuses to?
Intracranially cerebral veins
What blood vessels do emissary veins connect dural venous sinuses to?
Extracranially scalp veins
What is the course of travel of the cerebral veins into the bridging veins?
Where are the cerebral veins located?
Cerebral veins found in the subarachnoid space
Bridging veins branch from cerebral veins traversing the subdural space crossing the meningeal dural wall into the dural venous sinus
What is the significance of the point where the bridging vein connects to the dural wall?
Vein quite weak here so if it snaps can lead to venous blood filling the subdural space
What is the subdural space?
Potential space between arachnoid mater and dura mater
How do scalp veins (extracranial) connect with dural venous sinuses?
Scalp veins in dense connective tissue layer of scalp drain via emissary veins which travel through the skull bones to the dural venous sinus
Why could an injury to the scalp by potentially life threatening?
If the scalp develops an infection, the venous blood supply drains into dural venous sinuses which are intracranial meaning the infection can spread to intracranial structures
What are the 3 types of haemorrhage that can occur between the meningeal layers?
Extradural
Subdural
Subarachnoid
What is it called when bleeding occurs within the brain tissue itself? (Contusions, tearing of white matter)
Intracerebral haemorrhage
Why are intracranial haemorrhages very dangerous?
Increases the intracranial pressure due to the skul having. Fixed volume
This leads to compression and damage to brain tissue, brainstem and other structures like cranial nerves
What type of bleed is an Extradural haemorrhage?
(Arterial or venous)?
Arterial bleed
What blood vessel gets ruptured in an extra dural haemorrhage?
Middle meningeal artery
Where does the middle meningeal artery run?
Between the periosteal layer of dura and the inner table of the skull bone
How does an Extradural haemorrhage appear on a CT head?
Lentiform appearance (biconvex)
Why does an Extradural haemorrhage have a lentiform appearance?
As it bleeds it strips the periosteal layer from the inner table of bone
But the lateral extension of the bleed is limited by the bone since the periosteal layer is very strong at the sutures so the blood cant peel it off
How does a bleed appear on a CT scan?
Bright white
What is a tell tale history of an extra dural haemorrhage?
Significant trauma to head
Loss of consciousness
Then relatively normal for an hour
After an hour there’s then rapid deterioration
What is the time period called where the patient is relatively normal before rapid deterioration with an Extradural haemorrhage?
Lucid interval
Where is the subdural space?
Between the dura and arachnoid mater
What type of bleed is a subdural haemorrhage?
(Arterial or venous)?
Venous
What blood vessels are usually responsible for a subdural haemorrhage?
Bridging veins from cerebral veins
Why does rupture of bridging veins lead to subdural haemorrhage?
There’s a point of weakness where the bridging vein joins the dural venous sinus
So if this snaps venous blood can fill subdural space
How does a subdural haemorrhage appear on a CT head?
Bright white crescent shape (which can span whole hemisphere)
Banana shape (Bridging veins)
What is a normal history for a patient with a subdural haemorrhage?
Normally trauma
Headache
Then patient gradually declines as the venous blood accumulates increasing the intracranial pressure
Why does an older patient not necessarily need a significant head injury to get a subdural haemorrhage whereas a young individual would need significant trauma?
Older peoples brain shrinks (cortical shrinkage) which puts tension on the bridging vein at the point which it joins the dural venous sinus making it prone to rupture in an older person
What type of bleed is a subarachnoid haemorrhage?
(Arterial or venous)?
Arterial bleed
What usually leads to a subarachnoid haemorrhage?
Trauma
Spontaneous rupture of blood vessel (aneurysm)
What arterial vessel usually receive trauma or ruptures due to aneurysm causing a subarachnoid haemorrhage?
Branch f the Circle of Willis
How does a subarachnoid haemorrhage present and why?
Sudden onset bad headache since blood highly irritating to meninges
Often fatal
How is a Subarachnoid haemorrhage diagnosed?
CT head (sooner its done/earlier ini the haemorrhage its imaged more likely to pick it up)
Lumbar puncture
What is being examined for in a lumbar puncture if the CT head is negative for a subarachnoid haemorrhage?
Testing CSF for haemoglobin degradation products
