6 - Meninges and Dural Folds Flashcards
What are the three layers of meninges in the brain and spinal cord?
- Pia Mater: follows all the irregularities
- Arachnoid: Dips into fissures but not other irregularities. Subarachnoid space contains CSF and cerebral blood vessels supplying brain
- Dura Mater: dense irregular CT. Doesn’t dip into any grooves. Potential subdural space but pressure from CSF pushes arachnoid against dura. Double layer in brain, one layer in spinal cord
What layers of the meninges does meningitis affect?
Leptomeninges: pia and arachnoid
What layer of the meninges are we looking at here?
What is a dural fold and a dural venous sinus?
- Outer dura fuses with inner table of periosteum
- Meningeal layer separates and dips down to form dural venous sinus filled with venous blood
- Two meningeal layers at the bottom of the sinus join together to form dural fold. Not all sinuses do this
What makes the cavernous sinus different to other dural venous sinuses?
- Contains lots of fibrous septae so it looks cavernous
- Contains internal carotid artery and cranial nerves, not just venous blood like other sinuses (OTOMCAT)
- Cranial floor either side of sella turcica
What are the two important dural folds in the brain?
FC: Attaches to crista galli of ethmoid/frontal crest of frontal bone and fuses with TC at the back. Separates the two hemispheres down the longitudinal fissure
TC: Covers the cerebellum, in the posterior cranial fossa. Attached to occipital posteriorly in grooves for transverse sinus, laterally attached to petrous of temporal and anteriorly to a and p clinoid processes. Midline open to allow mid brain through
What sinuses are being indicated on this diagram?
Star is showing the relation of the tentorum cerebelli
Cavernous sinus next to sella turcica
What is the role of the dural folds and when can they cause issues?
Herniation under rigid folds
Or herniation of brain through the foramen magnum
What is the role of dural venous sinuses?
What are the main dural venous sinuses in the skull?
Sup/Inf Petrosal: allows anything in cavernous to drain in sigmoid and then IJV
Cavernous: either side of sella turcica
Transverse: see grooves along occipital bone, drains into sigmoid
Straight: sits on TC and connects sup/inf saggital
Superior/Inf Saggital + Straight
Drains into Transverse -> Sigmoid -> IJV
Sup/Inf Petrosal -> Cavernous Sinus -> Sigmoid -> IJV
What is the confluence of sinuses?
Connecting point of the superior sagittal sinus, straight sinus, and occipital sinus
Label the following sinuses.
ALL DRAIN TOWARDS IJV
Where do cerebral and scalp veins drain to?
Cerebral: cross the arachnoid space via bridging veins to enter dural venous sinuses
Scalp: cross through bone via emissary veins from outside skull to inside skull to get to dural venous sinouses
What are the two broad categories of intracranial haemorrhage and what is this issue with these?
Intracerebral: bleeding within brain itself, e.g tearing of white matter
Extracerebral: extradural, subdural, subarachnoid
Addition of blood to fixed space leads to rise in pressure, brain could herniate and brain tissue, brain stem and cranial nerves can all be damaged
What is an extradural haemorraghe?
- Arterial bleed
- Blow to side of head rupturing middle meningeal artery
- Headache
- Evacuate by drilling skull and craniotomy
What is a subdural haemorraghe?
- Venous bleed
- Usually from bridging veins as they join the walls of the dura
- More common in elderly as cerebral atrophy puts tension on veins so weak
What is a subarachnoid haemorrage?
- Arterial bleed
- Secondary to trauma or rupture of vessel, e.g aneurysm from circle of Willis
- Blood in arachnoid space mixes with CSF and irritates brain
- Headache and meningism signs as meninges involved
How can you tell the difference between the three main extra-cerebral haemorraghes on CT?
- Extradural: lemon
- Subdural: banana
- Subarachnoid: blood in arachnoid space instead of less dense CSF
Label the following layers of the skull.
Arachnoid granulations/villi, are small projections of the arachnoidmembrane into the superior sagittal sinus and its major tributaries, involved in the absorption process of cerebrospinal fluid back to venous
If you were to get punched in the nose, what issues could this cause involving the falx cerebri?
The cingulate gyrus can get herniated under the falx cerebri, damaging it! Due to a space occupying lesion. Issues with processing emotions and behaviour regulation
