CSF, Hydrocephalus, Lumbar Puncture Flashcards
What is hydrocephalus?
Refers to general condition where there is an excess cerebrospinal fluid (CSF) within the intracranial space, and specifically the intraventricular spaces which cause dilation of the ventricles
What does CSF stand for?
Cerebro-spinal fluid
What does an excess of CSF cause to the ventricles in the brain?
Dilation
What is majority of CSF produced by?
Choroid plexus
Is the production of CSF a passive process?
No, is a metabolic process and requires ATP:
- Sodium is pumped into the subarachnoid space, and water follows from the blood vessels
Where is the choroid plexus primarily located?
Choroid plexus is primarily located in the lateral ventricles (temporal horn roofs, and floors of bodies), posterior 3rd ventricle roof and caudal 4th ventricle roof
How much CSF does the adult brain produce every day?
450-600cc’s
Normal production is the same as reabsorption
How does normal production of CSF compare to reabsorption?
The same
How if CSF distributed at any given moment?
At any given moment, there is about 150cc’s of CSF present in the average adult, with about 25cc of this being in the brain ventricles
So the CSF volume turns over 3 to 4 times everyday
Describe the steps of the CSF pathway?
- Begins in lateral ventricle (remember there is one at each side)
- Travels through foramen of Monro into the 3rd ventricle
- Passes through the cerebral aqueduct of Sylvius into the 4th ventricle
- Passes through either of two foramina of Luschka or the single foramen of Magendie
- Flows through subarachnoid space over and around the brain and spinal cord
- Reabsorbed into venous system through numerous arachnoid granulations along the dural venous sinuses
In what ventricle does CSF begin?
Lateral ventricle
What does CSF travel through to get from the lateral ventricles to the III ventricle?
Foramen of Monro
What does CSF travel through to get from III ventricle to IV ventricle?
Cerebral aquaduct of Sylvius
What does CSF travel through to get from IV ventricle to subarachnoid space?
Either of two foramina of Luschka or single foramen of Magendie
What is CSF reabsorbed through and into?
- Reabsorbed into venous system through numerous arachnoid granulations along the dural venous sinuses
What do arachnoid granulations contain to assist with reabsorption of CSF?
Arachnoid granulations contain arachnoid villi which function as pressure-dependent one way valves that open when the ICP is about 3-5cm H2O greater than dural venous sinus pressure
When do valves open to allow CSF reaborption?
When the ICP is about 3-5cm H2O greater than dural venous sinus pressure
Is CSF reabsorption a passive process?
Yes, is driven by pressure gradient between intracranial space (ICP) and the venous system (about CVP)
What are the two major types of hydrocephalus?
- Communicating hydrocephalus (CoH)
- Also known as non-obstructive hydrocephalus
- Non-communicating hydrocephalus (NCH)
- Also known as obstructive hydrocephalus
What is communicating hydrocephalus also called?
Non-obstructive hydrocephalus
What is non-communicating hydrocephalus also called?
Obstructive hydrocephalus
What does CoH stand for?
Communicating hydrocephalus
What does NCH stand for?
Non-communicating hydrocephalus
What is a consequence of the CSF pathway being open from start to finish?
CSF can travel freely from the choroid plexus to the arachnoid granulations, so no obstruction and communicating hydrocephalus
What is the cause of communicating hydrocephalus in vast majority of cases?
Problem with CSF reabsorption (reabsorption cannot keep pace with production)
How does CSF production compare to reabsorption in communicating hydrocephalus?
CSF production > resorption
What is the immediate consequence of CSF production being greater than reabsorption in communicating hydrocephalus?
Ventricles dilate uniformly and ICP rises
Most of the time communicating hydrocephalus is due to CSF production > reabsorption, but what can be the cause sometimes?
Very rarely, overproduction of CSF (rather than under absorption) leads to disruption of the balance and development of communicating hydrocephalus
This is rare, but Choroid Plexus Papillomas have been known to present in this way
What is a example of a disease that causes communicating hydrocephalus due to overproduction of CSF rather than under absorption?
Choroid plexus papillomas
What is the presentation of communicating hydrocephalus in children?
- In young children whose cranial sutures have not yet fused can see disproportional increase in head circumference to the rest of the body or failure to thrive
- In children with fused sutures/adults manifests with symptoms of increased intracranial pressure
- Papilledema
- Gait disturbance
- 6th cranial nerve palsy
- Upgaze difficulty
What is the aetiology of communicating hydrocephalus?
- Infection (incidence after bacterial meningitis can approach 30%)
- Subarachnoid haemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)
- Post-operative
- Head trauma
What kind of infection commonly causes communicating hydrocephalus?
Bacterial meningitis
How can a subarachnoid haemorrhage cause communicating hydrocephalus?
Blood and blood breakdown products cause scarring of arachnoid granulations
How does the severity of communicating hydrocephalus vary?
Communicating hydrocephalus is thought of as a gentle disruption between production and resorption of CSF that occurs over time, sometimes there is a sizable insult that causes acute disruption of balance and CSF resorption is suddenly and dramatically reduced
What happens to patients when communicating hydrocephalus develops quickly such as due to a rupture aneurysm impairing a significant number of arachnoid granulations?
Neurological decline can be rapid with patients becoming sleepy then obtunded, then requiring intubation
When does non-communicating hydrocephalus occur?
Occurs whenever there is any physical obstruction to normal flow of CSF before it leaves the ventricles
What is the aetiology of non-communicating hydrocephalus?
- Aqueductal stenosis
- Tumours/cancers/masses
- Cysts
- Infection
- Haemorrhage/haematoma
- Congenital malformations/conditions
What typically causes gradual development of non-communicating hydrocephalus and what causes acute development?
Gradual - processes that have developed over time
Acute - intraventricular bleed
In terms of mental status, what is acute hydrocephalus associated with?
Rapid mental status decline
What can be seen in a radiography for hydrocephalus?
Earliest finding is dilation of temporal horns of the lateral ventricles
In most younger patients these should be almost invisible
The third ventricle will become ballooned
Lateral ventricle size increase
Peripheral sulci effaced
What evans ratio indicates hydrocephalus?
30% (0.3)
What ventricular index indicates hydrocephalus?
>50