7. CSF & Hydrocephalus

Question 1

What is the nature of CSF and its flow?

Answer 1

clear and colorless fluid around the brain and spinal cord

produced primarily by choroid plexus*** (60-80%)

Question 2

What is choroid plexus?

Answer 2

found in lateral (65%)***, third, and fourth ventricle

consists of villous folds lined by epithelium with central core of highly vascularized CT

specialized layer of ependymal cells= choroidal epithelium, overlying these villi

Question 3

What are the components of the BBB?

Answer 3

1. Continuous tight junctions
2. BM provides structural support
3. Astrocytic foot processes necessary for BBB development
4. Transport carriers for glucose and essential aas (bc brain cells cant synthesize on own)
5. sodium ion transporters
6. metabolic processes within endothelial cells control entry of NTs

Question 4

What is important about the blood-CSF barrier?

Answer 4

separates CSF and blood, restricts passage of substances, more permeable than BBB

Tight junctions bw CHOROID CELLS (not endothelial cells like in BBB)

have fenestrations of endothelial cells

Question 5

What does an impairment in blood-CSF barrier lead to?

Answer 5

an increase in protein concentration in CSF

Question 6

What are the steps to form CSF?

Answer 6

1. Formation: filtered form moves from fenestrations to choroidal cells, movement is guided by difference in pressure between blood in capillaries and CSF
2. Fluid passes lining and goes into ventricles

Question 7

What is the composition of normal CSF? how do you test for it?

Answer 7

clear and colorless

few cells and low protein

does not differ qualitatively from plasma, but does quantitatively (much lower 20 vs. 7000 protein levels)

TEST by lumbar puncture (bw L4 and L5)

Question 8

What is the functional significance of CSF?

Answer 8

1. Protection: shock absorber- protects brain from damage by buffering brain and protects from sudden pressure/temperature changes
2. Buoyancy: brain immersed in fluid and so pressure at base of brain reduced and net weight reduced
3. Metabolic: one way flow of CSF to blood takes potentially harmful metabolites, drugs, and other substances AWAY from the brain
4. Endocrine medium for brain: serves to transport hormones to other areas of brain

Question 9

Where is the interventricular foramen of monroe located?

Answer 9

bw lateral and 3rd ventricle

Question 10

What is between the third and fourth ventricle?

Answer 10

cerebral aqueduct

Question 11

What is the flow of CSF?

Answer 11

lateral ventricle–> interventricular foramen of monroe–> third ventricle–> cerebral aqueduct–> fourth ventricle–> can exit out of foramen of luschka/lateral aperture or median aperture/foramen of magendie–> subarachnoid space –> absorption by arachnoid villi into sagittal sinuses

Question 12

What happens with flow of CNS if CSF pressure> venous pressure? opposite?

Answer 12

when CSF> venous pressure, it’ll flow into sinuses

if venous pressure higher, than it wont flow backwards (one way valve)

Question 13

What is hydrocephalus?

Answer 13

expansion of ventricular system on basis of an increase in volume of CSF contained within them (increase dilation and ICP)

may be due to: overpdtn of CSF (rare), under-asorption of CSF (at level of arachnoid villi), or obstruction of outflow of CSF from ventricles

Question 14

What are the types of hydrocephalus?

Answer 14

Communicating: non-obstructive

Non-communicating: obstructive

Question 15

What are the characteristics of communicating, non-obstructive hydrocephalus?

Answer 15

flow of CSF is blocked AFTER exits ventricles- due to abnormalities that inhibit the resorption of CSF, most often at level of arachnoid villi

get EQUAL enlargement of ventricles and ballooning of corpus callosum

Question 16

What is Normal Pressure hydrocephalus (NPH)?

Answer 16

Chronic communicating hydrocephalus

characterized by enlarged cerebral ventricles, with intermittently elevated CSF pressure

Question 17

What could NPH be due to?

Answer 17

could be due to: increased viscosity of CSF, altered elasticity of ventricular walls, impaired absorption due to prior meningitis or subarachnoid hemorrhage

Question 18

What triad of symptoms are associated with normal pressure hydrocephalus?**

Answer 18

Dementia, Apraxic gait, urinary incontinence

Question 19

What is Hydrocephalus Ex-Vacuo?

Answer 19

cortical atrophy; empty space filled with CSF in CT

compensatory enlargement of cerebral ventricles and subarachnoid spaces

Due to: brain atrophy (in dementias), post-traumatic brain injuries, some psychiatric disorders (schizo)

Question 20

Would you expect to see an increase in CSF pressure/ICP in hydrocephalus ex-vacuo?

Answer 20

NO (wont see in lumbar puncture, will be normal)

Question 21

What is obstructive/non-communicating hydrocephalus?

Answer 21

caused by CSF flow obstruction that occurs within ventricular system- enlargement is PROXIMAL to obstruction

obstruction can be congenital or acquired

depending on location of obstruction, there is selective dilation of ventricles

Question 22

What is the difference bw communicating and non-communicating hydrocephalus?

Answer 22

equally have distribution of dilation with ventricles and in non-communicating, can pinpoint where obstruction is bc of which ventricles are dilated

Question 23

What is aqueductal stenosis?

Answer 23

narrowing of cerebral aqueduct blocking flow of CSF; most likely place for blockage

causes: tumor compression, narrow aqueduct, gliosis (reactive change of glial cells in response to damage in CNS, increasing shear stress leading to more damage)

Question 24

What are common signs/Sx of aqueductal stenosis?

Answer 24

thunderclap headache (max pain from seconds to mins), papilledema, enlarge head (infants), cognitive/developmental delays, decreased level of consciousness, upward gaze palsy (difficult looking up), tremors

Question 25

What is Dandy-Walker malformation?

Answer 25

obstruction at outlet of 4th ventricle and cerebellar hypoplasia

congenital brain malformation (development of cerebellum and 4th ventricle)

involves complete or partial agenesis of cerebellar vermis

Question 26

What are Dandy-Walker cysts?

Answer 26

enlarged fourth ventricles in back of school

Question 27

What are symptoms of D-W malformation?

Answer 27

slow motor development, reading difficulties, skull size increase, irritability and vomiting

Question 28

What is Chiari 2 Malformation and what forms it?

Answer 28

displacement of MEDULLA, 4th VENTRICLE, and CEREBELLAR Vermisthrough forament

structural defects in brain and SC during fetal development, as result of genetic mutations or lack of certain vitamins maternal diet

Question 29

What is Chiari 2 Malformation usually accompanied by?

Answer 29

lumbosacral myelomeningocele (severe spina bifida when spinal canal and backbone do not close so spinal cord and meninges protrude through back)

hydrocephalus seen in 90% of these cases

Get more severe as go up

Question 30

What is Acquired hydrocephalus?

Answer 30

develops later in life, occurs when something happens to prevent CSF in brain from draining properly

Question 31

What are the causes of Acquired hydrocephalus?

Answer 31

brain tumor or cyst, blocked CSF flow, bleeding inside brain (subarachnoid hemorrhage), head trauma, infection (meningitis)