7. CSF & Hydrocephalus Flashcards
What is the nature of CSF and its flow?
clear and colorless fluid around the brain and spinal cord
produced primarily by choroid plexus*** (60-80%)
What is choroid plexus?
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
What are the components of the BBB?
- Continuous tight junctions
- BM provides structural support
- Astrocytic foot processes necessary for BBB development
- Transport carriers for glucose and essential aas (bc brain cells cant synthesize on own)
- sodium ion transporters
- metabolic processes within endothelial cells control entry of NTs
What is important about the blood-CSF barrier?
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
What does an impairment in blood-CSF barrier lead to?
an increase in protein concentration in CSF
What are the steps to form CSF?
- Formation: filtered form moves from fenestrations to choroidal cells, movement is guided by difference in pressure between blood in capillaries and CSF
- Fluid passes lining and goes into ventricles
What is the composition of normal CSF? how do you test for it?
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)
What is the functional significance of CSF?
- Protection: shock absorber- protects brain from damage by buffering brain and protects from sudden pressure/temperature changes
- Buoyancy: brain immersed in fluid and so pressure at base of brain reduced and net weight reduced
- Metabolic: one way flow of CSF to blood takes potentially harmful metabolites, drugs, and other substances AWAY from the brain
- Endocrine medium for brain: serves to transport hormones to other areas of brain
Where is the interventricular foramen of monroe located?
bw lateral and 3rd ventricle
What is between the third and fourth ventricle?
cerebral aqueduct
What is the flow of CSF?
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
What happens with flow of CNS if CSF pressure> venous pressure? opposite?
when CSF> venous pressure, it’ll flow into sinuses
if venous pressure higher, than it wont flow backwards (one way valve)
What is hydrocephalus?
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
What are the types of hydrocephalus?
Communicating: non-obstructive
Non-communicating: obstructive
What are the characteristics of communicating, non-obstructive hydrocephalus?
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
What is Normal Pressure hydrocephalus (NPH)?
Chronic communicating hydrocephalus
characterized by enlarged cerebral ventricles, with intermittently elevated CSF pressure
What could NPH be due to?
could be due to: increased viscosity of CSF, altered elasticity of ventricular walls, impaired absorption due to prior meningitis or subarachnoid hemorrhage
What triad of symptoms are associated with normal pressure hydrocephalus?**
Dementia, Apraxic gait, urinary incontinence
What is Hydrocephalus Ex-Vacuo?
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)
Would you expect to see an increase in CSF pressure/ICP in hydrocephalus ex-vacuo?
NO (wont see in lumbar puncture, will be normal)
What is obstructive/non-communicating hydrocephalus?
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
What is the difference bw communicating and non-communicating hydrocephalus?
equally have distribution of dilation with ventricles and in non-communicating, can pinpoint where obstruction is bc of which ventricles are dilated
What is aqueductal stenosis?
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)
What are common signs/Sx of aqueductal stenosis?
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
What is Dandy-Walker malformation?
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
What are Dandy-Walker cysts?
enlarged fourth ventricles in back of school
What are symptoms of D-W malformation?
slow motor development, reading difficulties, skull size increase, irritability and vomiting
What is Chiari 2 Malformation and what forms it?
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
What is Chiari 2 Malformation usually accompanied by?
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
What is Acquired hydrocephalus?
develops later in life, occurs when something happens to prevent CSF in brain from draining properly
What are the causes of Acquired hydrocephalus?
brain tumor or cyst, blocked CSF flow, bleeding inside brain (subarachnoid hemorrhage), head trauma, infection (meningitis)
