CSF, hydrocephalus and lumbar puncture Flashcards
What is Hydrocephalus?
A general condition whereby there is excess Cerebro-Spinal Fluid (CSF) within the intracranial space and, specifically, the intraventricular spaces within the brain…causing dilation of the ventricles, and a wide range of symptoms.
What produces the majority of CSF?
Choroid plexus
Mechanism behind CSF production
metabolically active process (i.e. requires ATP) whereby sodium is pumped into the subarachnoid space, and water follows from the blood vessels.
Where is the choroid plexus located?
lateral ventricles (temporal horn roofs, and floors of bodies)
posterior 3rd ventricle roof
4th ventricle roof
How much CSF does the average adult produce?
450 and 600 cubic centimeters of CSF every day
normally, production = resorption
CSF vol turns over 3-4 x every day, with only a very small fraction of the CSF being in the ventricles at any given time, even though the majority of it is produced there
Describe the CSF pathway
From the 2 lateral ventricles the CSF travels through the foramen of monro into the 3rd ventricle
it then passes through the cerebral acqueduct into the 4th ventricle
It exits the 4th ventricle through either of two Foramina of Luschka or Foramen of Magendie
After exiting 4th ventricle - CSF flows through subarachnoid space over and around the brain and spinal cord and is eventually reabsorbed into venous system through arachnoid granulations in the dural venous sinuses
What is special about the arachnoid villi within the granulations?
They function as pressure-dependent one-way valves that open when the ICP is greater than dural venous sinus pressure.
Describe CSF resorption
passive process driven by the pressure gradient between the intracranial space (ICP) and the venous system (CVP)
What are the 2 major distinctions of hydrocephalus
Communicating Hydrocephalus (CoH) - Also known as “non-obstructive” hydrocephalus
Non-communicating Hydrocephalus (NCH)
Also known as “obstructive” hydrocephalus
What is communicating hydrocephalus?
If the CSF pathway is “open from start to finish,” meaning CSF can travel freely from the choroid plexus to the arachnoid granulations, then you have “no obstruction” and a communicating hydrocephalus.
In the vast majority of cases this represents a problem with CSF resorption; simply put, it cannot keep the pace with CSF production.
Pro>res
as a result the ventricular system dilates uniformly and ICP rises
What is non-communicating hydrocephalus?
If the CSF can’t travel freely from start to finish, then you’ve got an “obstruction” and non-communicating hydrocephalus.
Any physical obstruction to the normal flow
What is a rare cause of communicating hydrocephalus
Very rarely, there is overproduction of CSF (rather than under-absorption) which leads to disruption of this balance, and development of communicating hydrocephalus.
Choroid plexus papillomas can present this way
Signs/symptoms of communicating hydrocephalus in young children whose cranial sutures have not yet fused
Disproportional increase in head circumference compared to the rest of the face/body
Failure to thrive
Signs/symptoms of communicating hydrocephalus in children with fused sutures/adults
hydrocephalus manifests with symptoms of increased ICP;
Headache Nause and vomiting Papilloedema - O.D swelling Gait disturbance 6th cranial nerve palsy upgaze difficulty.
Aetiologies of communicating hydrocephalus (4)
Infection (incidence after bacterial meningitis can approach 30%)
Subarachnoid haemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)
Post-operative
Head trauma
