02.1 Environment of the brain, bleeds and hydrocephalus Flashcards
What are the functions of cerebrospinal fluid?
Protection - Cushions the brain
Buoyoncy - reduces the net weight of the brain
Chemical stability - low potassium allows the brain to function
Briefly describe the general circulation of cerebrospinal fluid.
Lateral ventricles (I + II) Third Ventricle (made by the borders of the right and left thalamus) Cerebral aqueduct Fourth Ventricle Central canal
What drains the CSF?
Arachnoid granulations drain the CSF into the dural venous sinuses.
What are the main blood vessels supplying the brain and what vessels are they derived from?
Anterior and Middle Cerebral arteries from the Internal Carotids
Basilar and Posterior Cerebral Arteries from the Vertebral arteries
What does the anterior cerebral artery supply?
Medial portion of the cerebral hemispheres
What does the middle cerebral artery supply?
Lateral portion of the cerebral hemispheres
What does the posterior cerebral artery supply?
Posterior brain
What does the basilar artery supply?
Cerebellum and brainstem
How do the cerebral arteries join?
Circle of Willis. Anterior and posterior communicating arteries form a ring at the base of the brain.
What are the meningeal layers?
Periosteal dura
Meningeal dura
Archnoid mater
Pia mater
Which layer of the meninges forms the falx cerebri?
Meningeal dura
Which meningeal layer prevents encephalitis?
Pia mater prevents bacteria entering the brain.
What are the 3 main types of intracranial hemorrhage?
Extradural haematoma
Subdural haematoma
Subarachnoid haemorrhage
What is the usual cause of an extradural haematoma?
Trauma. Pterion fracture and the middle meningeal artery being severed.
What type of vessel is an extradural bleed from?
Artery
What causes a subdural haematoma?
Bridging veins being damaged
What layers does an extradural haematoma occur between?
Skull and periosteal dura
What layers does a subdural haemorrhage occur between?
Dura mater and Arachnoid mater
What type of vessel causes a subdural haemorrhage?
Veins
What causes a subarachnoid haemorrhage?
Berry aneurysms bursting
Who is at a greater risk of berry anuerysm formation?
Polycystic kidney disease
What is hydrocephalus?
An abnormal collection of CSF in the ventricles leading to raised ICP
What is communicating hydrocephalus?
No flow obstruction. Usually due to impairment of reabsorption by arachnoid granulations
What is non-communicating hydrocephalus?
Flow obstruction. Usually of the cerebral aqueduct.
How can hydrocephalus be treated?
Peritoneal shunt
What forms the blood brain barrier?
Tight vascular endothelial junctions
Feet of astrocytes
Interneurones ‘plug the gaps’
What can move across the blood brain barrier?
Water, O2, CO2 can freely move
Glucose and amino acids are transported
