L4.2 Meninges Flashcards
What are the layers of Cranial Dura mater and the difference between spinal dura mater
Cranial dura mater has 2 layers whereas spinal only has one.
- Outer Periosteal layer: continuous with periosteum on outer surface of skull at intracranial foramina
- Inner: Meningeal layer close to arachnoid: continuous with spinal meninges
What are the two types of structures formed by cranial dura mater
- Intracranial venous sinuses: made from double layers of meningeal dura mater or dura/periosteal
- Dural partitions: meningeal layers sticking together which project inward and incompletely separate parts of the brain
Describe the path of venous drainage of the brain through dural venous sinuses
- Networks of small venous channels drain to
- a) Veins that penetrate meningeal dura: Cerebellar Veins in subarachnoid space
b) Veins that penetrate periosteal dura
- Diploic veins (between internal and external tables of compact bone)
- Emissary veins (from outside of cranial cavity- route of infection)
- Drain to the venous sinuses:
Superior sagittal sinus meets the inferior via the straight sinus. - Drain to the Confluence of the sinuses
- Continue as the Left and right transverse sinuses
- Continue as Sigmoid sinuses, receiving contributions from superior petrosal, cavernous sinuses
- Goes through Jugular foramen
- Becomes internal jugular vein
What is the inferior sagittal sinus made of compared to superior
Inf is made of only meningeal dura whereas superior sagittal is between periosteal and meningeal dura
What are the paired structures running within and in the wall of the cavernous sinuses, from top to bottom
In wall:
- Occulomotor CN3
- Trochlear CN4
Within:
- Internal carotid artery
- Abducent (CN6)
In wall:
- Opthalamic div. of Trigeminal (V1)
- Maxillary div of Trigeminal (V2)
What are the 4 Dural partitions, what sections are they dividing
- Falx cerebri: Separates left and right hemisphere
- Falx cerebelli: Separates right and left cerebellar hemispheres
- Tentorium cerebelli: Separates cerebellum from cerebrum horizontally
- Diaphragma Sellae: roofs the hypophyseal (pituitary) fossa in the sella tursica of sphenoid bone
What is the innervation of the Dura mater
All branches of the Trigeminal nerve
V1: anterior cranial fossa, tentorium cerebelli , post part of falx cerebri
V2: medial middle cranial fossa,
V3: lateral middle cranial fossa
Vagus Nerve CNX
and the 1st, 2nd and 3rd Cervical nerves = posterior cranial fossa
What is the blood supply to the dura mater and where does it travel
These arteries travel in the outer periosteal layer of the dura.
There is a small Anterior, accessory and Posterior meningeal artery with Middle Meningeal doing majority.
Middle meningeal enters skull through foramen spinosum and divides into anterior branch (crosses pterion) and posterior branch.
Compare the structure of the Arachnoid mater to Pia mater
Both are thin membranes.
Arachnoid is avascular and lines inner surface of dura mater. It has trabeculae into the sub arachnoid space and puts arachnoid granulations/villi into the CSF. It doesn’t enter grooves or fissures except for longitudinal fissure between hemispheres. Whereas
Pia: invests in the surface (grooves and fissures) of brain.
What is an extradural haemorrhage: causes, associations, blood collection/presentation
- Usually caused by arterial tear in middle meningeal branch in temporoparietal region.
- Skull fracture, blow to head.
-Blood collects between calvarium and periosteal layer of dura.
Bleed has clear edges on CT
What is an subdural haemorrhage: causes, associations, blood collection/presentation
- Caused by damage to cerebral veins that cross the subdural space to enter the superior sagittal sinus
- More likely in elderly with cerebral atrophy: more CSF space: more pressure on veins, anticoagulant users: increased venous pressure.
- Chronic is more common but can be acute following high velocity trauma.
- Presents with unclear margins: diffuse
What is an subarachnoid haemorrhage: causes, associations, blood collection/presentation
- Usually caused by arterial bleeding from a ruptured cerebral artery aneurysm from the circle of Willis.
- Associated with intracerebral bleeding. Blood in subarachnoid space.
- Patients have undergone significant cerebral trauma: causes sudden headache, vomiting and loss of consciousness
Presents on CT as brightness in star shape in basal cisterns
