Term
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Definition
outline of ventricular system
choroid plexus in orange
-lines top of 3rd ventricle
-bottom of lateral ventricles
-separately in 4th ventricle |
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Term
| basica anatomy of ventricular system |
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Definition
2 lateral ventricles pass to the 3rd ventricle via the 2 Foramen of Munroe
3rd ventricle goes to 4th, via the Aqueduct of Slyvius
4th ventricle delivers CSF to subarachnoic space via 3 channels: 2 lateral Foramen of Lushka and 1 medial Foramen of Magendie |
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Term
basic anatomy of the ventricular system
compartments and "ways out" |
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Definition
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Term
| anatomy around the lateral ventricles |
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Definition
bordered on top by the corpus callosum
medially, forniceal columns and laterally by part of decsneding motor pathway
-expansion of the ventricles can thus have memory and motor effects |
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Term
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Definition
| located in the roof of the 3rd ventricle and lateral ventricles; separately in the 4th ventricle |
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Term
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Definition
made of mesenchymal tissue
chorioid epithelium serves as boundary between the choroid plexus and the ventricular system = blood brain barrier
-lots of tight junctions
contains/needs carbonic anhydrase within the epithelium to make CSF |
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Term
choroid plexus
regulation of CSF production |
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Definition
CSF production is INDEPENDENT of the body's ICP and BP over normal physiologic ranges...just keeps makin' it!
interruption to the process of reabsorption --> hydrocephalus |
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Term
|
Definition
pump dependent mechanisms on the choroid interstitial side of the choroidal epithelium exchange bicarb for Cl-
Cl- passively moves across the epithelium cell and into the ventricular space, obligating water/fluid/CSF to move with it
making CSF is essentially the transfer of fluid (filtered from the blood) from the choroid interstitium to the ventricles |
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Term
production of CSF
role of carbonic anhydrase |
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Definition
enzyme necessary for the build of bicard in the choroidal epithelium cell to exchange for Cl-
blocking this enzyme with the drug Acetazolamide can reduce some CSF production |
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Term
| non-choroidal CSF production |
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Definition
20% of CSF is make outside of the choroid plexus:
-cerebral vasculature
-ependyma (lining tissue of the ventricles)
-pia, arachnoid layers
for this reason, obliterating the choroid plexus (choroid plexctomy) does NOT eliminate hydrocephalus |
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Term
|
Definition
BI-directional
CSF moves make and forth with the cardiac cycle
------>
<--- |
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Term
|
Definition
where a lot of CSF collects
in between the pia mater and arachnoid layer of dura |
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Term
|
Definition
[image]
traditional method of absorption is venous absorption via arachnoid granulations
areas where dura splits and granulation pokes through dura from subarachnoid space and returns to venous system through a fine membrane (membrane prevents blood from entering CSF space) |
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Term
| extracellular fluid movement |
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Definition
there is trans-ependymal flow of CSF
CSF can move through the ependyma (lining of the ventricles) into the brain itself
(-if this happens in excess, it can be pathologic)
fluid from the brain extracellular matrix can move into the ventricles |
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Term
CSF absorption
proposed alternative sites |
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Definition
olfactory lymphatics - transit through the cribiform plate
perivascular spaces around the vesicles (other than saggital sinus)
dural root sleeves |
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Term
| daily balance of CSF production/storage/reabsorption |
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Definition
everyday, the body replaces its entire CSF volume multiple times
neonates: 25ml/day (vol = 5-10 ml)
adults: 450 ml/day (vol = 150 ml) |
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Term
| implications of rate of CSF turnover |
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Definition
amount of fluid removed in a typical LP (~5ml) is quickly replaced by the body
if the CSF pathway is acutely obstructed, CSF build-up will occur quickly |
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Term
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Definition
elastance = d-Presssure / d-Volume
compliance = d-volume / d-pressure
the brain is fairly compressable, especially over time, and these values can change over time and are different among patients |
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Term
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Definition
[image]
important to consider the reaction of the brain to a growing mass
intracranial pressure will depend on the size of the ventricle (amount of expansion) AND the response of the brain to compression
as ventricles enlarge, there is an initial period of compensation by the brain
at some volume, compensation of the brain can't continue, and symptoms of ICP appear |
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Term
|
Definition
protects brain from injury (bouyancy)
buffers changes in volume of brain and blood
harmonic resonance - allow non-pulsative capillary blood flow
may play a role in nutrient/waste management |
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Term
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Definition
[image]
CSF flow buffers aterial flow so that the capillaries experience a more constant flow |
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Term
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Definition
| occurs when CSF production exceeds CSF reabsorption |
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Term
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Definition
CSF overproduction (rare!)
obstruction of flow
insufficient reabsorption |
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Term
hydrocephalus
CSF overproduction |
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Definition
very RARE
choroid plexus papilloma - tumor or choroid plexus
choroid plexus hyperplasia |
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Term
| obstructive hydrocephalus |
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Definition
blockage that typically occurs in the narrowed spaces: Foramen of Munrone, Aqueduct of Slyvius; which causes an expansion of the ventricular system upstream of the block
bloackage can also ocur at the outflow of the 4th ventricle to subarachnoic space (Lushka, Magendie) |
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Term
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Definition
expanded lateral and 3rd ventricle spaces
4th ventricle space relatively normal
expansion of tectum causing blockage of the Foramen of Sylvius |
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Term
| obstructive hydrocephalus and LP risk |
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Definition
it is important to make sure that a patient does not have obstructions before preforming an LP
fluid is subarachnoid space helps keep the brain in place so if some gets removed via LP and the obstruction present it fro be replaced, a herniation can develop |
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Term
| communicating hydrocephalus |
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Definition
blockage in the subarachnoid space
possible causes include infection or hemorrhage |
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Term
| types of communicating hydrocephalus |
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Definition
classic
external
normal pressure
pseudotumor cerebri |
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Term
| classic communicating hydrocephalus |
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Definition
blockage outside of the ventricular system (IVH, SAH)
ALL ventricles are enlarged
can happen in adults and kids |
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Term
|
Definition
pediatric communicating hydrocephalus that is usually benign/self-limiting
dilation of the subarachnoid space
diff dx: chronic subdural hematoma |
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Term
benign external hydrocephalus
presentation |
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Definition
child less that one year old
macrocephaly
full fontanelle
mild gross motor delay
otherwise normal development |
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Term
| benign external hydrocephalus imaging |
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Definition
| imaging shows frontally expanded subarachnoid spaces; normal sized ventricles [image] |
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Term
benign external hydrocephalus
natural history |
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Definition
fairly benign, 80-90% resolve spontaneously over 6-18 months
macrocephaly persists
subsequent development normal unless other malformations present |
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Term
| normal pressure hydrocephalus |
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Definition
communicating type of hydrocephalus
a treatable cause of dementia
brain with a "low spring constant"
etiology unknown; issue of too much compliance |
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Term
normal pressure hydrocephalus
presentation |
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Definition
elderly patient
gait disturbance
incontinence
dementia |
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Term
normal pressure hydrocephalus
imaging |
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Definition
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Term
normal pressure hydrocephalus
intracranial pressure |
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Definition
| brain parenchyma does not generate sufficient resistance to compression to raise ICP, so it remain normal |
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Term
normal pressure hydrocephalus
diagnosis |
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Definition
| rule out other causes of brain atrophy: dementia/Alzheimer's |
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Term
normal pressure hydrocephalus
treatment |
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Definition
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Term
pseudotumor cerebri
(idiopathic intracranial hypertension) |
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Definition
ventricular pressure is insufficient to overcome brain's resistance to compression results in increased ICP with normal sized ventricles
exact pathophysiology is unknown but a presumed outflow obstruction
low compliance bran resists compression |
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Term
| pseudotumor cerebri presentation |
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Definition
| classically seen in obese females headache visual field loss *papilledema* |
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Term
pseudotumor cerebri
images and ICP |
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Definition
essentially normal MRI; normal ventricular size
ICP is > 25-30 mmHg |
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Term
pseudotumor cerebri
treatment options |
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Definition
medical management - Acetazolamind
CSF shunt
optic nerve sheath fenestration |
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|
Term
| etiology of infant/neonatal hydrocephalus |
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Definition
| can be either congenital or aquired |
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Term
etiology of infant/neonatal hydrocephalus
congenital conditions |
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Definition
*Myelomeningocele (about 80% of cases)
Dandy Walker
X-linked
primary aqueductal stenosis (of Sylvius)
encephalocele |
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Term
etiology of infant/neonatal hydrocephalus
acquired conditions |
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Definition
*intraventricular hemorrhage
neonatal meningitis
venous outflow obstruction/ECMO (rare) |
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Term
|
Definition
80% incidence of hydrocephalus
associated Chiari II malformation
disruption of absorption by amniotic fluid exposure
increased risk of meningitis from exposure of CSF to outside environment
incidence of hydrocephalus may be reduced when malformation is closed in-utero |
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Term
|
Definition
cerebellum doesn't develop normally, born with a dilated cyst behind cerebellum
problem with fluid getting from lateral to 4th ventricle
[image] |
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Term
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Definition
| occurs mostly in prematurely born infants due to problems arising from the germinal matrix |
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Term
IVH in newborns
what is the germinal matrix? |
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Definition
sub-ependymal vascular layer in the fetus that serves as the "nursery for neurons" - all neurons arise from here and migrate out to the cortex
has a very rich blood supply, however this is not able to tolerate the cardiovascular changes that happen after birth, so it involutes at 32-34 weeks
infants born before 32 weeks are therefore at an increased risk of hemorrhage |
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Term
IVH in newborns
risk factors |
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Definition
| anything that raises cerebral perfusion pressure and cerebral blood flow |
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Term
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Definition
4 grades of IVH -- higher grades are associated with more chance of getting hydrocephaly
as grade increases, proportion of patients with post-hemmorhange ventricular dilation and need for treatment (shunt) both increase
more blood in the system - more likely to block outflow pathways |
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Term
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Definition
| hydrocephalus correlates with degree of hemorrhage escaping into the space blocking up the subarachnoid space with blood makes it more difficult for CSF to get back to venous system can cause hydrocephalus in children an adults (e.g. ruptured aneurysm) |
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Term
| postulated causes of post hemorrhagic hydrocephalus |
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Definition
there may be a role the TGF-beta and VEGF play
these are stimulated/up-regulated in arachnoid tissue after hemorrhage and may prohibit granulations from doing their job in the role of reabsorption of CSF
stimulation of extracellular matrix proteins leading to obstruction |
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Term
| acquired hydrocephalus causes |
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Definition
infection
mass lesion
arachnoid inflammatory processes |
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Term
| infectious causes of acquired hydrocephalus |
|
Definition
meningitis
neurocysticercosis |
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Term
| mass lesion causes of acquired hydrocephalus |
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Definition
tumor blocking the CSF outflow
carcinomatous meningitis |
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Term
| arachnoid inflammatory process causes of acquired hydrocephalus |
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Definition
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Term
| general presentation of hydrocephalus |
|
Definition
overt symptoms: headache, nausea/vomiting, lethargy/sleepiness, coma, suset eyes, 6th nerve palsy (eyes deviate medially)
insidious: deteriorating intellect, visual deterioration, papilledema/optic atrophy |
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Term
|
Definition
| optic disk should have a sharp border |
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Term
| hydrocephalus presentation in children |
|
Definition
overt: irritable, tense fontanelle, bradycardia, distended scalp veins, split sutures, neck stiffness or reduces range of motion (from carrying around such a big, heavy head!)
insidious: enlarging HC, separated sutures, prominent forehead, missed developmental milestones, feeding intolerance/vomiting |
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|
Term
older adult presentation of hydrocephalus
classis triad of NPH presentation |
|
Definition
ataxia/gait disturbance
incontinence
dementia |
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Term
| diagnostic imaging for hydrocephalus |
|
Definition
CT, MRI to image: ventricular size, tranependymal CSF flow, etiology
XR: not first choice, may show split sutures, copper beaten skill, empty sella (where pituitary should sit)
pressure measurementsL LP, ICP monitor, ventriculostomy |
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Term
| differential diagnosis of hydrocephalus |
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Definition
normal variation in ventricle size
Ex Vacuo dilation of the ventricles
compensated/arrested hydrocephalus |
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Term
| Ex Vacuo dilatation of the ventricles |
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Definition
ventricles enlarging due to "vacuum effect" of having less brain matter
less brain = more fluid
may also result from encephalomalacia after injury/insult (loss of tissue with trauma) |
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Term
| compensated hydrocephalus |
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Definition
with only a slight degree of obstruction, can establish a new equilibrium with minor rise in pressure and increase in volume
can be stable |
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Term
|
Definition
| same as compensated - new equilibrium established after a period of hydrocephalous in which the ventricles never fully returned to normal size |
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Term
natural history of acute hydrocephalus
(without treatment) |
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Definition
with acute blockage:
rapid progression of symptoms
early death or disability |
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|
Term
natural history of progressive hydrocephalus
(without treatment) |
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Definition
dramatic macrocephaly
loss of developmental milestones
progressive neurocognitive decline |
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Term
| natural history of arrested/compensated hydrocephalus |
|
Definition
unclear
may lead to mild cognitive impairment, nut unproven
many cases asymptomatic, with normal mentation
variability |
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Term
treatment of hydrocephalus
non-operative options |
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Definition
Acetazolamide (carbonic anhydrase inhibitor)
-IIH
serial lumbar punctures
-communicating hydro
-newborn IVH |
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|
Term
treatment of hydrocephalus
operative treatment options |
|
Definition
CSF shunt
endoscopic third ventriculostomy |
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Term
|
Definition
most common treatment
diverts CSF build up to other places in the body for absoprtiong:
-peritoneum
-vascular space
-pleural space |
|
|
Term
|
Definition
proximal catheter that gets inserted into the brain
rickham reservoir to allow acecess to CSF/brain (assess proximal catheter function, measure ICP, CSF for culture)
valve to regulate outflow of fluid (don't want to drain all of it!)
distal tubing |
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Term
|
Definition
shunt are very easier to put in, low risk related to placement procedure (2-5% chance of major hemorrhage)
shunt failure within the first 2 years after placement is a common clinical problem
-34% fail in 1 year
-50-65% fail in 2 years |
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|
Term
endoscopic third ventriculostomsy
ETV |
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Definition
| poking a hole in the very thin wall of the third ventricle leading to the subarachnoid space |
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Term
|
Definition
55-80% successful in selected patients
1% procedural mortality
3-6% late ETV failure can occur from the hole closing up or scarring over |
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Term
|
Definition
-catheter obstruction by brain/choroid
-catheter fracture or valve failure
-failure of distal site to absorb
-overdrainage by shunt (subdural hematoma from stretch of veins)
-infection (usually within 1st year after shunt failure; usually caused in OR)
- |
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Term
| acute management of shunt failure |
|
Definition
recognition by history and physical exam
imaging studies (comparison scans important!)
confirmatory tests via: shunt tap, ICP monitoring, injection studies |
|
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Term
| importance of comparison images |
|
Definition
ventricles can appear normal to too small in a shunt failure can
good to know what the patient looks like on imaging when the shunt is working properly in order to know when it is acting pathologically |
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Term
|
Definition
most often from strep and staph - diagnosed from CSF culture
usually shows up within first year |
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Term
| treatment of shunt infection |
|
Definition
shunt removal
antibiotics
shunt replacement |
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Term
|
Definition
can be helpful to figure out complicated cases
important to get multiple readings as there is variability of pressure over time |
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