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.
How is CSF produced?
The majority of CSF is produced by the choroid plexus within the brain through a 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 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 is produced each day?
The average adult brain produces between 450 and 600 cc’s of CSF every day.
What is the turn over of CSF each day?
So, the CSF volume turns over three to four times 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
How much CSF is there in the body?
At any given moment, there is only ~150 cc’s of CSF present in the average adult; of this, only ~25 cc’s is within the brain ventricles
What is the pathway of CSF flow?
- From the lateral ventricle, CSF travels through the foramen of Monro into the 3rd ventricle (midline), then passes through the Cerebral Aqueduct [of Sylvius] into the 4th ventricle.
- It then exits the 4th ventricle through either of two Foramina of Luschka (“L” is for Lateral/Luschka) or the single Foramen of Magendie (“M” is for Midline/Magendie).
Where is the CSF reabsorbed?
After exiting the 4th ventricle, the CSF flows through the subarachnoid space over and around the brain and spinal cord, and is eventually reabsorbed into the venous system through numerous arachnoid granulations along the dural venous sinuses (especially the superior sagittal sinus).
What do the arachnoid granulations contain?
Arachnoid granulations contain arachnoid villi, which function as pressure-dependent one-way valves that open when the ICP is ~3 to 5 cm H20 greater than dural venous sinus pressure.
What kind of process is CSF production?
CSF production is a metabolically active process which uses ATP
What kind of process is CSF reabsorption?
CSF resorption is a passive process
What drives CSF reabsorption?
It is driven by the pressure gradient between the intracranial space (ICP) and the venous system (~CVP
What are the distinct types of hydrocephalus?
- Communicating hydrocephalus (CoH)
- Non-communicating hydrocephalus (NCH)
What is communicating hydrocephalus also known as?
Non-obstructive hydrocephalus
What is non-communicating hydrocephalus also known as?
Obstructive hydrocephalus
When is hydrocephalus 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.
When is hydrocephalus non-communicating hydrocephalus?
If the CSF can’t travel freely from start to finish, then you’ve got an “obstruction” and non-communicating hydrocephalus.
What is normally the problem in communicating hydrocephalus?
In the vast, vast majority of cases, this represents a problem with CSF resorption; simply put, it cannot keep the pace with CSF production.
What does CSF production> resorption result in?
As a result, the ventricular system dilates uniformly, and ICP rises.
What is a rare cause of CoH?
Very rarely, there is overproduction of CSF (rather than under-absorption) which leads to disruption of this balance, and development of communicating hydrocephalus.
What can cause overproduction of CSF?
Choroid plexus papillomas
What are the signs and symptoms of CoH in young children?
In young children whose cranial sutures have not yet fused, you can see disproportional increase in head circumference compared to the rest of the face/body or failure to thrive
What are the signs and symptoms of CoH in older children?
In children with fused sutures/adults, hydrocephalus manifests with symptoms of increased intracranial pressure;
-H/A, N/V, papilledema, gait disturbance, 6th cranial nerve palsy, upgaze difficulty, etc.
What is the aetiology of CoH?
- Infection (incidence after bacterial meningitis can approach 30%)
- Subarachnoid Hemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)
- Post-operative
- Head trauma
When can hydrocephalus develop very quickly?
Sometimes there can be a sizeable insult that causes an acute disruption of the balance, and CSF resorption is suddenly (and dramatically) reduced
How can patients present with acute (emeregency) CoH hydrocephalus?
Neurological decline can be rapid, with patients becoming sleepy, then obtunded, then requiring intubation.
When does NCH occur?
Non-communicating hydrocephalus occurs whenever there is ANY physical obstruction to the normal flow of CSF before it leaves the ventricles.
What can cause NCH?
- Aqueductal stenosis
- Tumors/Cancers/Masses
- Cysts
- Infection
- Hemorrhage/hematoma
- Congenital malformations/conditions
- Etc.
Where can NCH occur
Non-communicating hydrocephalus can result from CSF flow obstruction at any point along the intraventricular pathway.
What cause gradual symptoms of NCH?
Processes that have developed over longer periods of time (i.e. masses, etc) usually cause gradual development of symptoms.
How do acute processes present in NCH?
Acute processes (i.e. intraventricular bleed) can cause acute obstruction with rapid mental status decline.
What is the earliest consistent radio graphical indicative development of hydrocephalus?
Dilation of the temporal horns of the lateral ventricles. In most younger and middle-aged patients, these should be almost invisible.
What can be seen on radiology of hydrocephalus?
- The third ventricle will become ballooned
- Lateral ventricle size increase
- Peripheral sulci effaced
- Evans Ratio ->30% /Ventricular index >50%
What is the mode of treatment for hydrocephalus?
Surgical
How is acute hydrocephalus treated?
Acute hydrocephalus, whether communicating or not, usually necessitates urgent or emergent placement of an External Ventricular Drain (EVD - catheter passed through the patient’s scalp and skull into lateral ventricle, that drains CSF to a collection system kept at the patient’s bedside).
What can EVD be replaced with?
EVD cannot be maintained indefinitely; usually, if the patient is unable to tolerate weaning/clamping of the EVD prior to removal, a permanent shunt will be required.
What is the infection risk of EVD?
High
What is the mainstay of treatment for CoH?
For communicating hydrocephalus, the mainstay of treatment is shunt placement.
What types of shunts can be used to treat CoH?
- Ventriculo-peritoneal is most used.
- Lumbar-peritoneal sometimes utilized, though overdrainage is a problem.
- Ventriculo-atrial can also be considered in cases of peritoneal failure
How can a small number of acute CoH patients by managed?
Acute communicating hydrocephalus patients (i.e. SAH) can sometimes be managed with EVD with successful weaning and no shunt placement, but a significant number of these patients eventually need shunt placement weeks or months later.
How is NCH treated?
NCH treatment also surgical, but sometimes shunt can be avoided by removing the obstructing lesion.
Give examples of lesions which can be removed in NCH?
- Colloid cyst at anterior 3rd ventricle causing ball/valve obstruction of Foramen of Monro.
- Pineal region tumor causing compression of cerebral aqueduct.
- Ependymoma blocking 4th ventricular CSF outlets.
What s ventriculostomy often performed in conjunction with?
Often performed in conjunction with VP shunt placement.
