Ventricular System Flashcards
What is tela choroidae?
Penetrating choroidal artery with invaginating pia mater, vascular bundle and efferent choroidal vein
From what is the choroid plexus formed?
Tela choroidae covered by ependymal cells
How does choroid plexus functionally produce CSF?
Ependymal cells lining tela choroidea have active secretory Na pumps
Cl follows the Na passively to maintain electroneutrality.
H2O is pulled with it.
Ependymal cells also possess glucose transporters and can transport glucose from blood but these are less effective, therefore CSF [glucose] < [serum glucose]
Rough [csf glucose] : [serum glucose]
0.66 : 1
Which substances are transported from csf to the vascular tuft of the tela choroidae?
K
What is the name for the distal dilatation of the spinal canal?
Terminal ventricle
What is the name of the dilatated subarachnoid space into which foramen luschke open?
(Cerebello)Pontine cistern
Into which subarachnoid swelling does the foramen Magendie open?
Cerebellomedullary cistern (cisterna magna)
In which portion of the lateral ventricle is the foramen of Monro found?
Body of lateral ventricle
How low does the subarachnoid space extend?
S2
What are the names of the two layers of dura mater?
Periosteal layer
Meningeal layer
What cell type lines dural venous sinsus?
Endothelium
What is an arachnoid granulation
Macroscopic view of arachnoid mater projecting into dural venous sinuses as arachnoid villi.
How does CSF move through arachnoid villi to venous drainage?
Via vesicular channels between endothelial cells
What are the key functions of CSF?
Cushion of protection
Buoyancy
Reservoir regulating intracranial contents/pressure
Nourishment
Metabolic waste removal
Hormone transport
What is the weight of brain when suspended in CSF?
50g
What is the mechanism through which raised ICP causes projectile vomiting?
Traction on vagus nerves
Leptomeninges=
Pia and arachnoid mater
Colour of normal CSF
Clear
Cellular composition of normal CSF
Lymphocytes- <5/mm^3
No RBC
No neutrophils
Glucose in normal CSF
[2/3 serum]
As less efficiently transported
Normal level of protein in CSF
<0.4g/L
Colour of CSF
in pyogenic bacterial meningitis
Yellow/turbid
Colour of CSF
in TB meningitis
Turbid +/- fibrin web
Colour of CSF
in viral meningitis
Clear
Cell count in
Pyogenic bacterial meningitis
High levels of neutrophils
Low lymphocytes (acute rather than chronic inflammation)
Cell profile in TB meningitis
Low neutrophils (chronic rather than acute inflammation)
High lymphocytes
Cell profile in viral meningitis
Low neutrophils (chronic rather than acute inflammation)
High lymphocytes
Glucose level in pyogenic meningitis
[<50% serum]
Bacteria use glucose
Glucose level in TB meningitis
[<50% serum]
Bacteria use glucose
Glucose level in viral meningitis
[>50% serum glucose]
Protein in pyogenic bacterial meningitis
Increased significantly
Protein in TB meningitis
Significantly increased
Protein in viral meningitis
<=1g/L
Def: Hydrocephalus
Excessive CSF within cranial cavity
Causes of hydrocephalus in simple terms
Excess production
Abnormal circulation
Impaired drainage
Causes of excessive CSF production?
Choroid plexus papilloma
Non-communicating hydrocephalus
(Obstructive)
CSF from within the ventricular system is not able to communicate with subarachnoid space
Communicating hydrocephalus
CSF able to flow from ventricular system to subarachnoid space
Queckenstedt’s Test
Test for spinal blockage of CSF using lumbar manometer
With occlusion of IJV manually, there should be increase in CSF pressure.
If there is no increase this indicates blockage of the spinal subarachnoid space
Positive if abnormal- i.e. no increase in CSF pressure with IJV occlusion
What constitutes blood-CSF barrier?
Tight junctions between choroidal epithelial cells (in contrast to BBB which is due to tight junctions between endothelial cells)
Macroscopic appearance of ependyma
The distinctive, shiny white appearance
Embryological associations of the CSF ventricles
Lateral-> telencephalon
Third-> diencephalon
Fourth- rhombencephalon
What is the embryological precursor to the aqueduct of Sylvius?
The lumen of the mesencephalon
Def: Frontal horn
The portion of the lateral ventricle anterior to the foramen of Monro continuous posteriorly with the body of the lateral ventricle.
If no choroid plexus is seen on entering the lateral ventricle, what is the likely location of the endoscope?
Anterior horn as there is no choroid plexus
Location of the body of the lateral ventricle
Predominantly in the parietal lobe
Continuous anteriorly with the frontal horn and posteriorly with the atrium
Extends from the foramen of Monro anteriorly to the limit of the septum pellucidum posteriorly
What is the limit of the septum pellucidum posteriorly
Where the fornix fuses with the corpus callosum
What divides the caudate from the thalamus in the lateral ventricle?
The caudothalamic grooove (striothalamic sulcus)
Contains the stria terminalis and thalamostriate vein
What is the benefit of identifying the choroid plexus when in the lateral ventricle?
Following it anteriorly will reliably lead to the foramen of Monro
Comminucations of the atrium (trigone)
Anterosuperiorly-> body
Anteroinferiorly-> temporal horn
Posteriorly-> occipital horn
Medial wall of the atrium
Superiorly the bulb of the corpus callosum
inferiorly the calcar avis (which overlies the calcarine sulcus)
Lateral wall of the atrium
Caudate nucleus and the tapetum of the corpus callosum
Floor of the atrium
Collateral trigone, which overlies the collateral sulcus
Roof of the atrium
Corpus callosum
Where is the most voluminous colloid plexus in the brain found?
In the atrium and is referred to as the choroid glomus which may contain benign, incidental choroid cysts and often becomes calcified with age
Boundaries of the temporal horn
Floor
Made up of the hippocampus medially and the collateral eminence laterally
Floor of the third ventricle
Bounder anteriorly by the optic chiasm and posteriorly by the opening of the cerebral aqueduct.
From A->P:
Optic chiasma, infundibulum, tuber cinereum, mamillary bodies, posterior perforated substance and mesencephalon.
Recesses of the third ventricle
Chiasmatlc recess into the angle formed by the attachment of the chiasm to the anterior wall
Infundibular recess
Bulging or rounding out of these recesses is an early indicator of HCP
What is the surgically important area of the floor of the third
Between the hypothalamus and the tuber cinereum