CSF, Hydrocephalus and LP Flashcards
Definition of hydrocephalus
A general condition whereby there is an excess CSF within the intracranial space and specifically, the intraventricular spaces within the brain - causing dilatation of the ventricles and a wide range of symptoms
Where is the majority of CSF produced by?
Choroid plexus
How is CSF produced?
Metabolically active process within the brain (requires ATP) whereby sodium is pumped into the subarachnoid space, and water follows from the blood vessels
Where is choroid plexus located?
Lateral ventricles - temporal horn roofs - floor of bodies Posterior 3rd ventricle roof Caudal 4th ventricle roof
Where is the biggest choroid plexus found?
Lateral ventricle
What is the mechanism of CSF flow?
Flows from the two lateral ventricles into the 3rd ventricle (through the foramen of munro) then down the aqueduct into the 4th ventricle.
Then out through the megendie foramen (single and midline) and two Luschcka foramen (lateral)
After exiting the 4th ventricle, flows through 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 (esp the superior sagital sinus
How many cc’s does an average adult brain produce?
450 - 600 ccs
Normally, production of CSF = what?
Resorption of CSF
What do arachnoid granulations contain?
Arachnoid villi
Two 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
What is communicating hydrocephalus?
CSF pathway 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
What is non communicating hydrocephalus?
If CSF cannot travel freely from start to finish, then youve got an “obstruction” and non communicating hydrocephalus
What does communicating hydrocephalus usually represent a problem with?
CSF reabsorption - which cannot keep up with the rate of CSF production
Result of communicating hydrocephalus
As the ventricular system dilates uniformly, the ICP rises
Pathology of communicating hydrocephalus
Underabsorption of CSF
Overproduction of CSF (RARE)
Presentation of communicating hydrocephalus
Young children whose sutures havent fused yet
- disproportional increased in head circumference
- failure to thrive
Children with fused sutures / adults
- symptoms of increased ICP; Headache, nausea and vomiting, gait distrubance, 6th cranial nerve palsy, papilloedema, upgaze difficulty
Causes of Communicating hydrocephalus
Infection (e.g. bacterial meningitis)
Subarachnoid haemorrhage (blood and blood breakdown products cause scarring of arachnoid granulations)
Post op
Head trauma
Causes of non communicating hydrocephalus
Aqueductal stenosis Tumours / cancers / metastases Cysts Infection Haemorrhage/haematoma Congenital malformations/conditions
How quickly do the symptoms of non communicating hydrocephalus come on?
Processes that have developed over long periods of time - more gradual symptoms (i.e. masses etc) Acute processes (i.e. intraventricular bleed) can cause acute obstruction with rapid mental status decline
What is the earliest radiographic finding of non communicating hydrocephalus?
Dilatation of temporal horns of the lateral ventricles
Radiographic findings of non communicating hydrocephalus
First dilatation of temporal horns
Third ventricle becomes ballooned
Lateral ventricle will increase in size
Peripheral sulci effaced
An evans ratio greater than or equal to 0.3 defines what?
Ventriculomegaly
Treatment of acute hydrocephalus
Urgent or emergency placement of extra ventricular drain (EVD)
How does an EVD work?
Catheter passed through the patient’s scalp and skull into the lateral ventricle, that drains CSF to a collecting system kept at the patients bedside
Treatment of communicating hydrocephalus
Shunt placement
Types of shunt used to treat communicating hydrocephalus
Ventriculo-peritoneal
Lumbar peritoneal
Ventricular atrio
What is the most common type of shunt used in communicating hydrocephalus?
Ventriculo-peritoneal shunt
Treatment of non communicating hydrocephalus
Removing obstructive lesion
+/- Shunt
Possibly a third ventriculostomy
How does a third ventriculostomy work?
Often performed in conjunction with BP shunt placement
Hole is opened surgically in the floor of the third ventricle so CSF flows out into the interpeduncular cistern and pre-pontine space (bypasses cerebral aqueduct)
Causes of VP shunt failure
Mechanical failure from occlusion/disconnection Migration Overdrainage/underdrainage Infection Skin erosion
What % of shunts fail 5 years after placement?
50%
What % of shunts can fail in the first year?
40%
What does NPH stand for?
Normal pressure hydrocephalus
What is NPH a rare preventable cause of?
Dementia
Classic triad of NPH
Wet, wobbly and wacky