Meninges and dural folds Flashcards
What is the meninges?
Three membranous layers that surround and protect the brain and spinal cord
What are the 3 layers of the meninges?
pia mater - covers the whole CNS (every fissure and sulcus) and brain steam
arachnoid mater - loose connective tissue just surround fissures
dura mater - outer most layer
What is between pia mater and arachnoid layer?
subarachnoid space containing blood vessels and CSF
What are the leptomeninges?
pia and arachnoid layers collectively
What is between arachnoid layer and dura mater?
potential space called the subdural space HOWEVER< normally the pressure of the CSF in the subarachnoid space pushes the arachnoid layer to the dura mater
What is the dura mater?
tough fibrous membrane - fuses with the periosteum lining inner table of skull bones
What is special about the arachnoid layer?
it is soft and translucent
What are the 2 layers of dura?
periosteal and meningeal
What is the periosteal layer of dura?
the part against the inner table of bone
What is the meningeal layer?
the part adjacent to the arachnoid
Where do these 2 layers separate?
They are normally closely adhered, but they separate where there are dural fold and dural venous sinuses
What is a dural fold?
- Meningeal dura form it as a fold coming toward the midline - it runs in between fissures on the cranial vault e.g.
Falx cerebri : (longitudinal fissure) seperates both cerebral hemispheres
Tentorium cerebelli : (lateral fissure) seperetes occipital from cerebellum
What is a dural venous sinus?
Meningeal dura separates from periosteal layer and a plexus of veins are found there
- they are connected to eacother and receive blood from cerebral veins
What is the clinical significance of dural folds?
they are very rigid and help stabilise the brain acting as rigid dividers
- a rise in intracranial pressure secondary to bleed etc can lead to compression and herniation of parts of brain under the dural folds or through the foramen magnum
Where do dural venous sinuses ultimately drain into?
IJV as soon as they pass through the jugular foramen
What do bridging veins do?
connect cerebral veins in the subarachnoid space to the dural venous sinus
What do emissary veins do?
connect scalp veins in the dense connective tissue to the dural venous sinuses
What is the difference in their paths through the head and brain?
Bridging veins traverse the subdural space but emissary veins travers through the skull
What can head traumas lead to?
intracranial haemorrhage - blood vessels run along in-between the meningeal layers
What can head traumas lead to?
intracranial haemorrhage - blood vessels run along in-between the meningeal layers
Where can you get haemorrhaging?
in the spaces between the meningeal layers; Extradural subdural subarachnoid intracerebral
What is an extradural haemotoma caused by?
- MMA bleed (arterial)
- lucid interval - unconscious then ok then deteriorate
- often secondary to trauma to side of head (pterion)
- doesn’t cross suture lines as the periosteal dural is stripped off the inner bone - the dura is strongly adhered to the suture lines
- get a biconvex shape on CT scan
What is a subdural haemotoma caused by?
- bridging veins bleed (venous)
- looks like a banana on CT scan
- mainly elderly (brain shrinks causing bridging veins to be stretched making them easier to snap cortical atrophy
- mild injury - later onset of symptoms as blood has time to pool (in dural venous sinuses)
What is a subarachnoid haematoma caused by?
- secondary to trauma or spontaneous rupture of blood vessel (anurysm) - usually branch of circle of willis
- severe sudden onset headache
- blood leaks into suparachnoid space and mixes with CSF
- need to perform lumbar puncture for confirmation
