Anatomic Basis of Hydrocephalus Flashcards
(54 cards)
1
Q
what is the foramen of monroe?
where is it located?
A
- the conduit between the lateral ventricles and 3rd ventricle
- insertion onto lateral ventricle divides the anterior horn from the body
- located in the frontal lobe
2
Q
what is the atrium?
where is it located?
A
- the junction between the superior lateral ventricle (anterior horn, body and posterior horn) and the inferior lateral ventricle (inferior horn)
- its insertion on the superior lateral ventricle divides in the anterior horn and the body
3
Q
the anterior horn of the ventricle is
- located in what lobe
- defined by what boundaries
A
- frontal lobe
- all of the temporal lobe rostral to the insertion of the foramen of monro
4
Q
the body of the lateral ventricle is
- located in what lobe
- defined by what boundaries
A
- located in?
- defined as the lateral ventricle
- caudal to the foramen of monroe
- rostral to the atrium
5
Q
the posterior lobe is
- located where
- defined by what boundaries
A
- in the occipital lobe
- defined as the lateral ventricle caudal to the atrium
6
Q
the inferior horn of the lateral venticle is
- located where?
- defined by what boundaries?
A
- in the temporal lobe
- extends anteroinferioly from the atrium
7
Q
describe the continuity of the lateral ventricles to one another
A
they are separated medially by the septum pellucidum (& have no direct connections), except briefly at the foramen of monroe / interventricular foramen
8
Q
into what does the foramen of monroe empty?
A
the midline of the third ventricle
9
Q
what is the most rostral midline ventricle?
A
the third ventricle
10
Q
the 3rd ventricle are
- made of what components?
- bordered rostrally by?
- bordered caudally by?
- bordered medially by?
A
- components:
- inferior expansion - in the hypothalamus
- caudal extension - travels thru midbrain (between tectum & tegmentum) -> the pons -> dilates into 4th ventricle
- bordered:
- rostrally - by the anterior commissure
- posteriorly - by the posterior commisure
- medially - by the lateral walls of the thalami in the middle of the ventricle
11
Q
the cerebral aqueduct
- travels how?
- forms what?
A
- in between the midbrain (separating tectum and tegmentum)
- expands into the 4th ventricle
12
Q
what borders the 4th ventricle is bordered by
- ventrally?
- dorsally?
- superiorly?
- inferiorly?
A
- ventrally: caudal (superior) pons + rostral (superior) medulla
- dorsally: ventral surface of the cerebellum
- superiorly:dilation of cerebral aqueduct
- inferiorly: the central canal
13
Q
what is the obex?
where is it located?
A
- triangular termination fo the 4th ventricle
- in line with the rotral medulla
14
Q
what is the fastigium?
where is it located?
A
- the widest portion of the 4th aqueduct
- in line with the caudal end of pons
15
Q
what are the aperatures of the brainstem?
where are they located?
what is their role?
A
- perforations of the 4th ventricle
- role: connects ventricular CSF to subarachnoid CSF
- locations:
- lateral aperature: just caudal to the end of the fastigium
- medial aperature: just rostral to the end of the obex
16
Q
median aperature
- other name
- definition
- role
- location
A
- name: foramen of magendie
- definition: perforation of the 4th ventricle
- role: connects ventricular CSF to subarachnoid CSF
- location: just above to the end of the obex (termination of 4th ventricle in line with rostral medulla)
17
Q
lateral aperature
- other name
- definition
- location
- role
A
- other name: foramen of luschka
- definition: perforation of the 4th ventricle
- connects ventricular CSF to subarachnoid CSF
- locations: just caudal to the fastigium (widest section of 4th ventricle, in line with caudal pons)
18
Q
list & describe the layers that comprise the blood brain barrier
A
-
endothelial cells:
- NON-FENESTRATED
- connected by tight junctions
-
basement membrane:
- CONTINUOUS
- EMBEDDED WITH PERICYTES
- perivascular tube feet of astrocytes
19
Q
how does fluid move across the blood brain barrier?
A
- there is minimal movement of fluid fom capillaries into blood
- this is due to the tight nature of the barrier, largely from
- non-fenestrated endothelium w/ tight junctions
- continuous basement membrane
20
Q
what attaches to the outer basement membrane forming the blood brain barrier?
A
pericytes
21
Q
the choroid plexus
- is derived from?
- is located where?
- has what role?
A
- derived from: pia mater & ependymal cells
- located: ventricles
- role: primary site of secretion of cerebrospinal fluid (CSF) from blood -> ventricles
22
Q
in what direction does fluid move across the barrier surrounding the choroid plexus? why?
A
from blood (choroid plexus) -> CSF
higher hydrostatic pressure of blood
23
Q
list & describe the layers that form the choroid plexus
A
- endothelial cells:
- FENESTRATED
- line with tight junctions
- basement membrane
- DISCONTINUOUS
- embedded within stroma: CT + immune cells
- epithelial cells (derived from ependymal cells)
- simple cuboidal
- have microvilli
- connected w/ zonula occludens & desmosomes
24
Q
the ependyma
- has what role?
- is located where?
A
- location: lines the ventricles & surface of central canal
- role: provides a barrier against transfer between CSF and neural tissue
25
list & describe the layers that form the ependyma
26
list and describe the layers that form the ependyma
* epithelium:
* simple columnar
* have microvilli
* connected by zonula occludens & desmosomes
* made of epyndmal cells + tanycytes:
* _ependymal cells:_ ciliated
* _tanycytes:_ send projections in neural tissue vasculature
* basement membrane
* perivascular tube feet of astrocytes
27
what are tanycytes?
where are they found?
what is their role?
* definition: a type of epithelial cell
* location: found in the empyndema epithelium lining ventricles & central canal
* role: extend _small cellular processes_ through the basement membrane to vessels in the surrounding nueural tissue, to perform *limited absorption / secretion of CSF*
28
the choroid plexus form what unique shape?
why is this important?
the form into villi
this allows for maximal surface area for CSF secetion
29
compare & constrast the endothelial cells of the
* BBB
* choroid plexus
* empendyma
* BBB: **non-fenestrated** w/ tight junctions
* choroid plexus: **fenestrated** w/ tight junctions
* ependyma: n/a
30
compare & contrast the basememt membranes of the
* BBB
* choroid plexus
* ependymal cells
* BBB:
* **_continuous_**
* _contain pericytes_
* lind with perivascular tube feet of astrocytes
* choroid plexus:
* **_discontinuous_**
* embedded in loose CT stroma
* ependymal cells
* _pierced with tanycyte processes_
* lined with perivascular tube feet of astrocytes
31
compare and contrast the epithelial linings of the
* BBB
* choroid plexus
* ependyma
* BBB - n/a
* choroid plexus & ependyma
* both:
* **columnar with microvilli**
* have demosomes & tight junctions
* derived from ependymal cells
* ependyma: ependymal cells (ciliated) + tanycytes (have foot processes)
32
where is the subarachnoid space?
between the pia mater and arachnoid mater
33
what determines the "depth" of the subarachnoid space?
why is this significant?
* the **length of the fine trabeculae** that connect the
* deep surface of subarabhnoid mater
* superficial surface of the pia mater
* this length throughout most of CNS is small - except at **cisterns:** deep subarachnoid spaces containing large amounts of CSF
34
what are the cisterns of the CNS?
where are they each located?
* **chiasmatic cistern:** surround the optic chiasms
* **interpeduncular cistern:** between cerebral peduncles + ventral space
* **pontine cistern:** around inferior pontine sulcus
* **cisterna magna (**cerebellomedullary) cistern:
* posterior (dorsal) medulla
* inferior surface of cerebellum + inferior surface of occipital bone
* **quadrageminal (**superior) cistern:
* immediately posterior (dorsal) to tectum + pineal gland
* along superior / inferior surfaces of tentorium cerebelli
* **lumbar cistern:**
* inferior to L2 (conus medullaris)
* superior to S2 (end of dura mater)
35
once the CSF reaches the 4th ventricles, it can go to which major locations?
* through _cantral canal_ of spinal cord -\> **pool in lumbar cistern.**
* through the _lateral aperature_ (just below fastigium) to the
* **ventral surface**
* **superior sagittal sinus**
* through the _median aperature_ (just below opex)
* **cisterna magna**: dorsal medulla + inf cerebellum / occipital bone
* **quadrigeminal cistern:** dorsal to tectum & pineal gland + superior & inferior surface of tectorium cerebelli
* **superior sagittal sinus**
36
where is the pontine (pontomedullary cistern located?
around the inferior pontine sulcus
37
the cisterna magna
* has what other name?
* is formed by what borders?
* receives CSF how?
* cerebellomedullary cisterna
* borders:
1. dorsal medulla
2. inferior cerebellum
3. inner occipital bone
* receives CSF from: median aperature
38
the quadrigminal cistern
* has what other name?
* is formed by what borders?
* receives CSF how?
* superior cistern
* borders
1. superior tetorium cerebelli
2. dorsal pineal gland
3. dorsal tectum
4. superior cerebellum / inferior tentorium cerebelli
* receives CSF via: cisterna magna
39
how does CSF get from the 4th ventricle to the superior sagittal sinus?
* two major routes:
* lateral aperature -\> ventral space -\> superior sagittal sinus
* median aperature -\> cistern manga -\> quadrigeminal cistern -\> superior cistern
40
the lumbar cistern
* what significance?
* has what borders?
* receives CSF how?
* significance: contains the caunda equina
* borders:
* L2 - conus medullaris
* S2 - end of dura mater
* receives CSF via the central canal
41
arachnoid granules
* definition
* location
* makeup
* role
* definition: evaginations of arachnoid mater that protrude into dura matter
* location: in between the _periosteal & meningeal dural layers_ speciifcally, which is where the _superior sagittal sinu_s courses
* makeup: only of _thin_ arachnoid membrane
* role: **delivers CSF from the cisterns into the superior sagittal sinus: i.e., major site of CNS absorption in the blood**
42
how does CSF move across the CSF-blood barrier seen at the arachnoid granulations?
why?
* blood moves into the sagittal sinus
* pressure of the CSF \> pressure of venous blood
43
how much does the adult brain weigh?
how does the presence of CSF change this?
1300 g
with CSF, the "effective" weight comes down to 45 g
44
what are the major sites of CSF production?
* choroid plexus
* pia matter arterioles
* deep to ependymal
45
how do changes in arterial and venous pressure alter CSF volume?
* arteries (choroid plexus): site of CSF secretion
* increased BP: increaes volume (increased secretion)
* decreased BP: decreased volume (decreased secretion)
* venous (sagittal venous sinus): site of CSF secretion
* increased BP: increases volume (less absorption)
* decreased BP: decreases volume (more absorption)
46
how does hypoventilation affect CSF volume?
why?
increases CSF volume
decreases peripheral vasculature resistance
47
what is the monro - killie hypothesis?
* that the skull is an elastic chamber filled with 3 compartments, and an increase in pressure / volume of one compartment results in a compensatory decrease in another
* blood
* brain
* CSF
48
the brain can accomodate for what changes of in intracanial volume up to what point? how?
increases beyond this point value result in what?
* can accomodate for changes up to 100 ml, via:
1. decerasing CSF production (minor)
2. **shifting more CSF into the spinal cord -\> lumbar cistern (major)**
* beyond 100 mL will result in one of three alterations:
1. _brain compression_: decreased ventricles
2. _midline shift_: brain out of line with falx cerebri
3. _herniation_: midline shift + herniation of cerebellum thru foramen magnum
49
what is hydrocephalus?
how does it generally present?
how is it treated?
* a marked increase in the volume of the ventricles
* generally, comes at the expense of the _rest of the brain_
* tx: **inserting a catheter in the lateral ventricles**
50
how does hydrocephalus present in newborns specifically?
* compensetory decrease in brain volumes (like with adults), +
* expansion of calvarial diameter
* expansion of the frontaneles
51
what are the two major classifications of hydrocephalus and what defines them?
* based on whether or not the CSF can leave the 4th ventricle into subarachnoid space
* communicating hydrocephalus: CSF can exit 4th ventricle
* non-communicating hydrocephalus CSF cannot exit 4th ventricle
52
what are the two major types of communicating hydrocephalus?
CSF movement from ventricle-subarachnoid space unimpeded
* **choroid plexus tumor**: increase in CSF output
* **dural scarring / hematoma:** decreased in CSF absorption
53
what are the two major types of non-communicating hydrocephalus?
movement of CSF from 4th ventricle to subarachoid space impeded
* **aqueductal stenosis** - congenital, tumor
* **4th ventricle blockage** - m/c cerebellar tumor
54
normal pressure hydrocephaly
* demographics
* presentation
* findigns
* treatment
* demographics: 60 yr +
* presentation:
1. gait impairment
2. cognitive decline
3. urinary incontinence
* findings: _increased volume yet normal pressure_
* imaging: ventricular increase + brain decrease
* lumbar spinal tap: normal CSF pressure
* treatment: nothing great; spinal tap = short term gait improvement
