Meninges, venous drainage of the brain and CSF Flashcards
What are the different layers of the Meninges ?
Meninges layers;
- Dura mater (tough fibrous bridges crevices, attached to skull)
- Arachnoid mater (delicate sealed bag for CSF; bridges crevices
- Arachnoid trabeculae (“ropes” across subarachnoid space that keeps it in place)
- Cerebral artery branch (embedded in Pia mater)
- Pia mater (delicate, dips into crevices)
What are the features of the dura mater and what does it contain ?
Thick tough durable “dura mater” coast the brain
Includes branches of the middle meningeal artery
Bridges the gaps (fissues, sulci) - supporting non distensible bag
What are the features of the arachnoid matter ?
- Delicate membrane
- Also bridges gaps
- A sealed bag for CSF in subarachnoid space
Where are the different cisterns in the arachnoid matter?
- Superior cistern (superior anterior to cerebellum)
- Interpeduncular cistern (between peduncles)
- Cisterna pontis (just below pons)
- Cistern magna (cerebellomedullaris - accessible in rare cases by neurosurgeon for CSF)
Where his the Arterial circle of Willis and what would happen if damage occurred here?
Arterial circle of Willis lies in a subarachnoid space
Can get a berry aneurysm of the circle of Willis and this can cause subarachnoid haemorrhage (clinical thunderclap sign).
Berry aneurysms most often occur from the posterior communicating arteries which arise from the ICA
What suspends the Pia mater?
Denticulate ligament (saw or tooth like)
Why are roots long at the caudal end?
Due to development, used to be close to orgin at S1 vertebra but growth of the vertebral column moves the root further away from the origin in the cord - giving us caudal equina look
Where would you sample CSF from?
You would do a lumbar puncture in the subarachnoid space
Well below so L3-5 (usually L4/5) as Caudal equina here
What are the features of the veins in the brain?
Veins of the brain;
- Have thin walls and no valves
- Emerge from brain and lie in subarachnoid space (In young and old these bridging veins can have mor atrophy in older and in younger are more delicate)
- Drain into cranial venous sinuses
- Grouped into external (quite variable) and internal cerebral veins
Name the internal cerebral veins ?
Image
Name the structures related to the deep veins above the thalamus ?
This is the floor of lateral ventricle - Thalamus is in floor of lateral ventricle
Deep veins;
- Vein of septum pellucidum (corpus callosum and deep medullary frontal white matter)
- Thalamostriate vein (vena terminalis) (drains caudate nucelus and putamen)
- Choroidal vein (drains choroid process of lateral ventricle)
- Deep structures are drained through internal cerebral vein and basal vein from temporal lobe into the Great cerebral vein (vein of Galen)
- Interventricular foramen (connect the left and the right lateral ventricles to the third ventricle)
- Choroid plexus of lateral ventricle (A network of blood vessels and cells in the ventricles (fluid-filled spaces) of the brain)
How are the venous sinuses related to the tentorium cerebelli?
They run around the parameters of the tentorium cerebellum
How does the dura fold and what is the significance of this ?
Dura folds inside the skull to form the falx cerebri and tentorrium cerbelli over the cerebellum and attaches at the tentorial notch
Midbrain sits here, a space occupying lesion can force bit of brain (E.g temporal lobe) through here and squashes brainstem and causes a life threatening event as affecting essential life senses (known as trans-tentorial herniation)
What does the brain do to prevent the impact of trauma ?
Compartmentalise decreases the energy of the individual bits of the brain and minimise effects of trauma
What happens in Trans-tentorial herniation?
A space occupying lesion is causing stuff to be pushed down and out into space
Can force bit of brain (E.g temporal lobe) down through the tectorial notch and squashes brainstem and causes a life threatening event as affecting essential life senses
What happens in subdural haemorrhage ?
A bleed in the space between the dura and arachnoid mater (subdural space)
How are the ventricles arranged?
- Lateral X2
- Interventricular foramen
- Aqueduct
- Third ventricle
- Fourth ventricle
How did we used to visualise ventricles?
Used to be visualised in conventional radiology by filling the spaces with air - only way to see on x-ray now have MRI so not needed
Name these ventricles on an MRI?
Image
Name these ventricles and structures on an MRI?
Image
How is CSF formed ?
CSF is formed in the choroid plexus (up to half from blood vessels surrounding the ventricles)
Core of vascular tissue (in Pia) covered by an epithelium which secretes cerebrospinal fluid
(epithelium differentiated from ependyma - classified as glial cells!)
Volume approx 150ml
Turnover approx x4 per day
Production approx 500ml
(75ml in cisterns, 50ml in sub arachnoid space and 25ml in ventricles)
Where does CSF flow to?
Choroid plexus makes CSF in all the ventricles
CSF flows out of the ventricle system into subarachnoid space via apertures in fourth ventricle
See image
How does CSF move from the subarachnoid space into the superior sagittal sinus?
Uptake of CSF from the subarachnoid space in arachnoid granulations and then superior sagittal sinus
