Meningeal Layers, Dural Folds And Dural Venous Sinuses Flashcards
What are the meninges? What is their function?
Three membranous layers that surround and protect the brain and spinal cord
Dura mater- dense Ct doesn’t dip
(CSF pressure pushes arachnoid against dura- potential space ‘subdura’)
Leptomeninges (affected by meningitis):
Arachnoid mater - loose CT, dips into fissures, soft, translucent
(Subarachnoid space - CSF and Bvs)
Pia mater- microscopically thin, dips into sulci, gyri and fissures
Gives buoyancy to protect the brain and spinal cord
Layers of the dura mater and what separation of these layers creates
Periosteum- coats bones, goes sutures to underside (also called periosteal)
Dura fuses with periosteum Dural layers (two-ply):
Periosteal- against the inner table of bone
Meningeal- adjacent to arachnoid (closest to brain)
Where the layers separate -> Dural venous sinus (filled with venous blood) and if layers continues past sinus and rejoin -> Dural fold
What is the cavernous venous sinus?
A sinus filled with: plexus of veins, internal carotid artery and cranial nerves 3-6 at base of skull on cranial floor
Thrombus can get in -> problems eye/ cranial nerves
What are the following structures and where are they found: falx cerebri, tentorium cerebelli and superior Sagittal sinus?
Falx cerebri - Dural fold runs in the longitudinal fissure between two hemispheres of the brain (vertical plane)
Tentorium cerebelli - Dural fold tent over cerebellum separates it from the inferior portion of the occipital lobe (horizontal plane)
Superior Sagittal sinus- 2 Dural venous sinuses along falx cerebri (where Dural layers re-separate)
Function of Dural folds and when can this go wrong?
Help to stabilise the brain and act as rigid dividers
But a rise in pressure inside the skull e.g. secondary to a bleed can lead to compression and displacement (herniation) of parts of the brain under rigid Dural folds and/ or through foramen magnum
Function of Dural venous sinuses and the path blood takes?
Found where meningeal and periosteal dural layers separate
Connect to each other and receive blood from cerebral veins to drain the brain, eventually they drain into the internal jugular vein
Dural venous sinuses drainage system
Superior Sagittal sinus, inferior Sagittal sinus, transverse sinus and occipital sinus all lead into the straight sinus -> inferior petrosal sinus -> cavernous sinus -> sphenopariteal sinus
Transverse sinus -> sigmoid sinus -> inferior and superior petrosal sinuses
Eventually all drain into the internal jugular vein (connected to the sigmoid sinus)
Slide 12
What drains into the Dural venous sinuses?
Cerebral veins drain into bridging veins which traverse the subdural space and connect to DVS
And scalp veins connect to DVS via emissary veins which traverse through the skull
Intracranial haemorrhage and intracerberal haemorrhage
Head trauma can lead to bleeding in spaces between meningeal layers
- extradural (between inner table of bone and periosteum) bleed strips periosteum off at edge of bone until reaches a suture and stops, haemorrhage pinches in
Intra-cranial (in layers of meninges):
- subdural -extradural
- subarachnoid
Intra-cerebral (in brain itself) e.g. contusions, tearing of white matter
Addition of volume to an already fixed space leads to a rise in pressure and damage to brain tissue, brain stem and other important structures
Extra cranial
-subaponeurotic
Extradural haemorrhage: potential cause, appearance, treatment, typical history
Arterial bleed
Fracture of pterion-> middle meningeal artery
Haemorrhage Lens shaped, sutures pinch it in
Surgically evacuate blood, drill into skull
Young pt side of head strike, lose consciousness -> region and be fine (lucid interval) but with severe headache. Next few hours gradually lose consciousness
Subdural haemorrhage: what happens, why is it more common in the elderly and appearance, general history
Venous bleed usually from bridging veins
Bridging vein breaks dura wall at weakest point
Older brain shrinks- tensions to bridging vein- can pull away from connections to DVS -> blood fills in potential subdural space
Banana shape
Elderly fall (no severe head trauma), consciousness gradually lost and confusion increases
Subarachnoid haemorrhage:
Cause, what, diagnosis, symptoms
Veins/ arteries/ CSF e.g. Emissary vein
Secondary to trauma or spontaneous rupture of blood vessel (aneurysm)
Usually a branch of circle of Willis
Blood leaks into subarachnoid space, mixing with CSF (sudden and often fatal)
Ct normally picks up, if not lumbar puncture to see if blood in CSF (Hb degradation products)
Headache, signs of meningeal irritation e.g. photophobia, stiff neck, nausea
But no: fever, sore throat, high temperature (signs of infection a.k.a meningitis)
What is a subaponeurotic haemorrhage?
Between periosteum of the skull and the aponeurosis of the scalp - emissary veins connect DVS
Extra cranial
