19 - Blood Brain Barrier and CSF Flashcards
What are the 3 layers of the cerebral meninges?
Dura - attached to skull, hard
Arachnoid - trabecular meshwork , spiders web
Pia - thin tight membrane, attached to bl of brain
Where are blood vessels found in the meninges?
Dura and arachnoid
Where are veins found in the meninges?
Inner layers of the dura and crossing the dura-arachnoid interface
What are the 3 types of cerebral haemorrhage?
- Epidural haemorrhage: Bleeding outside the dura, arterial, no symptoms then mins/hours later severe headache as haematoma compresses brain
- Subdural haemorrhage: Bleeding between dura and arachnoid, bridging veins, slow onset of symptoms (24h), blood spread all over brain surface
- Subarachnoid hemorrhage: Bleeding in arachnoid space, ruptured aneurysm, arterial symptoms, sudden severe thunderclap headache. Form of stroke
What is the difference between a epidural and subdural bleed?
- Epidural bleed: Usually arterial, rapidly increases in size, lens shaped in MRI, acute skull trauma,
- Subdural bleed: Veins bridging dura and arachnoid, more spread out MRI, road accident which moves brain relative to skull, venous bleed so slower, symptoms may show up in minutes but can be delayed as much as 2 wks
What is the falx?
A sheet of dura which extends to divide the hemispheres
What are the tentoria?
Pair of transverse sheets of dura which extend below the base of the occipital cerebrum
They divide the cerebrum above from the cerebellum below
What is the gap between the two tentorii called?
Tentorial incisure
What is in the cerebral ventricles?
Cerebrospinal fluid
What is cerebrospinal fluid formed by?
Choroid plexus - a meshwork of capillaries covered by ependymal cells
What does choroid plexus do?
Produce a protein-free filtrate from blood
What rate is cerebrospinal fluid produced at?
500ml/day
What does healthy CSF contain?
Very little protein No cells (not pH buffered like blood)
How much CSF does the brain hold? Where is it drained into?
135-150ml
Drained into the blood through arachnoid granulations in the superior sagittal sinus
How much plasma proteins are there in CSF? How is this measured?
0.3 - 1.0% plasma proteins
Measured by lumbar puncture