BRAIN & CSF
• Ventricles are four fluid filled cavities
located with in the brain. These are :
Two lateral ventricles.
The central canal in the spinal cord has a
small dilatation at its inferior end, referred
to as the terminal ventricle.
The ventricles are lined by an epithelial layer
known as ependyma & are filled with
The ventricles are developmentally derived
from the cavity of the neural tube.
These are two irregular cavities situated one in
each cerebral hemisphere
Each lateral ventricle consists of:
a central part
Three horns, anterior, posterior and inferior
THE CENTRAL PART
This part of lateral ventricle extends from the
interventricular foramen in front to the splenium of
the corpus callosum behind.
ROOF : formed by undersurface of corpus callosum
FLOOR : formed (from lateral to medial side) by:
a. Body of caudate nucleus
b. Stria terminalis
c. Thalamostriate vein
d. Lateral portion of upper surface of thalamus
MEDIAL WALL : Formed by- septum pellucidum
and body of fornix
Choroid fissure is a space between fornix and
upper surface of the thalamus
A fold of pia mater, the tela choroidea,
invaginates through the fissure & covers part of
The tela choroidea is common to the two lateral
ventricles, and to third ventricle
Within each lateral edge of the tela choroidea
there are plexuses of blood vessels that constitute
choroid plexus .
The tela choroidea & other structures forming
the walls of the ventricle are lined by ependyma.
A line along which choroid plexus invaginates into
It’s a c- shaped slit in medial wall of cerebral
Starts at interventricular foramen (above and in
front) & passes around the thalamus
Thus it is present only in relation to the central
part and inferior horn of the lateral ventricle
Its convex margin is bounded by fornix (body and
crus),and concave margin is bounded by the
thalamus (superior and posterior surfaces), the tail
of the caudate nucleus and the stria terminalis.
THE ANTERIOR HORN
This part lies in front of interventricular foramen
and extends into frontal lobe. It is directed
forwards, laterally and downwards
ANTERIOR : Posterior surface of genu and
rostrum of corpus callosum
ROOF : Anterior part of trunk of corpus callosum
a. Head of the caudate nucleus
b. Upper surface of the rostrum of the corpus
• MEDIAL :
a. Septum pellucidum
b. Column of fornix
THE POSTERIOR HORN
This part lies behind the splenium of corpus
callosum and extends into occipital lobe. It is
directed backwards and medially
FLOOR & MEDIAL WALL : shows 2 elevations
a) Upper,Bulb of posterior horn raised by
b) lower,Calcar avis raised by anterior part of
ROOF & LATERAL WALL : Tapetum
THE INFERIOR HORN
Largest horn of lateral ventricle. It begins at the
junction of the central part with the posterior
horn of lateral ventricle; and extends into the
ROOF ( & LATERAL WALL) :
a) Chiefly the tapetum
b) Tail of caudate nucleus
c) Stria terminalis
Collateral eminence raised by collateral sulcus
In the inferior horn, the line of ependymal
invagination by the choroid plexus ( i.e. the
choroid fissure ) lies b/w the stria terminalis
and the fimbria.
THIRD VENTRICLE is a median cleft b/w the two
Developmentally, it represents the cavity of
The cavity is lined by ependyma
Anterosuperiorly, on each side, it communicates
interventricular foramen (or foramen of monro)
This foramen is bounded anteriorly by the column
of fornix, and posteriorly by the tubercle of the
Posteroinferiorly, in the median plane, it
communicates with the fourth ventricle through
the cerebral aqueduct.
Recesses are extensions of the cavity. These are:
ANTERIOR WALL :
1) Lamina terminalis
2) Anterior commissure
3) Anterior columns of fornix
POSTERIOR WALL :
1) Pineal body
2) Posterior commissure (in the lower lamina
of pineal stalk)
3) Cerebral aqueduct
It is formed by the ependyma lining the under
surface of the tela choroidea of the third ventricle
The choroid plexus of the third ventricle projects
downwards from the roof
FLOOR : formed by hypothalamic structures
Infundibulum (pitiutary stalk)
Posterior perforated substance
Tegmentum of the midbrain
LATERAL WALL :
1) Medial surface of thalamus (in its posterosuperior
2) Hypothalamus (in its anteroinferior part)
3) The hypothalamus sulcus which separates the
thalamus from the hypothalamus. The sulcus
extends from the interventricular foramen to the
TELA CHOROIDEA OF THE THIRD
AND LATERAL VENTRICLES
Its a double layered fold of piamater that occupies
the interval b/w splenium of corpus callosum and
fornix, above, & the two thalami below.
It is triangular in shape
Its posterior end is broad & lies in the gap b/w the
splenium (above) & posterior part of the roof of the
third ventricle (below)
The anterior end (representing the apex of
triangle) lies near the left & right interventricular
The median part of the tela choroidea lies on the
roof of third ventricle
Its right & left lateral edges project into the
central parts of the corresponding lateral ventricles.
Highly vascular structures that are responsible for
formation of CSF
Surface of each plexus is lined by a membrane
formed by fusion of ventricular ependyma with pia
mater of tela choroidea.
Deep to this membrane there is plexus of blood
Microscopically, surface of choroid plexus has
numerous villous processes.
The blood supply of tela chroidea and choroid
plexuses of lateral & third ventricle is derived from
choroidal branches of internal carotid and basilar
The venous blood drains in to the internal cerebral
veins,which unite to form the great cerebral vein.
4 choroid plexuses are seen in relation to the
tela choroidea of third and lateral ventricles.
Two of these (one right & one left) lie along the
corresponding lateral margins; & project into
central part of corresponding lateral ventricle.
Two other plexuses run parallel to each other,
one on either side of midline.
These are choroid plexuses of third ventricle.
At each posterolateral angle of tela choroidea
the choroid plexus of lateral ventricle continues
into inferior horn.
The cerebral aqueduct( aqueduct of sylvius), a
narrow channel about ¾ of an inch long, connects
the third ventricle with forth ventricle.
It is lined with ependyma and is sorrounded by a
layer of gray matter called the central grey.
There is no choroid plexus in the cerebral
• The fourth ventricle is a tent shaped cavity filled
with cerebrospinal fluid. It is situated anterior to the
cerebellum and posterior to the pons and medulla
• It is lined with ependyma and is continuous above
with cerebral aqueduct of midbrain & below with
central canal of medulla oblongta and spinal cord.
• The fourth ventricle posssess lateral boundaries , a
roof , and a rhomboid shaped floor.
The caudal part of each lateral boundary is formed
by the inferior cerebellar peduncle.
The cranial part of each lateral boundary is formed
by superior cerebellar peduncle.
Roof / Posterior wall
The tent shaped roof projects in to the cerebellum.
The superior part of the roof is formed by superior
medullary velum and inferior part by inferior
This part of the roof is peirced in the midline by a
large aperture(median aperture of foramen of
Lateral recesses extend laterally around the sides
of the medulla and open anteriorly as the lateral
openings of the fourth ventricle or foramen of
Floor / Rhomboid fossa
• The diamond shaped floor is formed by the
posterior surface of the pons & medulla oblongta.
The floor is divided in to symetrical halves by the
• On each side of sulcus, there is an elevation , the
medial eminence which is bounded laterally by
another sulcus, the sulcus limitans.
• Lateral to this sulcus limitans, there is a vestibular
area & vestibular nuclei lies behind it.
• The facial colliculus is a slight swelling at the
inferior end of the medial eminence that is
produced by the fibres from the motor nucleus of
the facial nerve.
• Strand of nerve fibres, the stria medullaris ,
emerge from the median sulcus & pass laterally
over the median eminence and the vestibular area
& enter the inferior cerebellar peduncle to reach
• Inferior to the stria medullaris, the most medial
structure is the hypoglossal triangle & hypoglossal
nucleus lies underneath it.
• Lateral to this is vagal triangle , beneath which
motor nucleus of vagus nerve lies.
Choroid Plexus of Fourth Ventricle
The choroid plexus has a T shape; the vertical part
of the T is double. It is suspended from the
inferior half of the roof of the ventricle & is
formed from the highly vascular tela choridea.
The blood supply to the plexus is from the
posterior inferior cerebellar arteries.
Central canal of the spinal cord &
The central canal opens superiorly in to the fourth
ventricle, inferiorly it extends to the medulla
oblongta & spinal cord.
In the conus medullaris of spinal cord , it expands
to form terminal ventricle .
The central canal is sorrounded by gray matter &
there is no choroid plexus in the central canal.
CSF is found in the ventricles of the brain and
in the subarachnoid space around the brain &
It is a clear, colourless fluid
It possesses, in solution, inorganic salts similar
to those in the blood plasma
The glucose content is about half of blood, &
there is only a trace of protein
The pressure of CSF may be raised by
straining, coughing, or compressing the internal
jugular veins in the neck.
Physical characteristics & composition
of the CSF
Clear and colourless
Rate of production
Pressure(spinal tap with patient in
lateral recumbant position)
60-150mm of water
No. of cells
0-3 lymphocytes/cu mm
FUNCTIONS OF THE CSF
Cushions & protects the CNS from trauma
Provides mechanical buoyancy & support
for the brain
Serves as a reservoir & assists in the
regulation of the contents of the skull
Nourishes the CNS
Removes metabolites from the CNS
Serves as a pathway for the pineal
secretions to reach the pitiutary gland
The CSF also acts
as a “water jacket”
for the brain and
The 1300 g adult
approximately 45 g
when suspended in
CLINICAL NOTES OF VENTRICLES
The third ventricle is a narrow space wnich is
easily obstructed by local brain tumours or by
developmental defects. The obstruction leads to
raised ICP in adults & hydrocephalus in children
Tumours in the lower part of the third ventricle
give rise to hypothalamic symptoms, like
diabetes insipidus, obesity etc.
The site of obstruction can be found out by
In these scans the third ventricle is seen,
normally as a narrow, vertical midline shadow.
Dilatation of third ventricle would indicate
obstruction at a lower level, e.g. the cerebral
If the obstruction is in the third ventricle,
both the lateral ventricles are dilated
Obstruction at the interventricular foramen
causes unilateral dilatation of the lateral
ventricle of that side.
Vital centres are situated in the vicinity of
vagal triangle. An injury to this area is
Infratentorial brain tumours
medulloblastomas block the median & lateral
foramina situated in the roof of the ventricle.
This results in marked & early rise of ICP
In arnold chiari deformity the medulla &
the tonsils of the cerebellum come to lie
in the vertebral canal.
Apertures in the roof of fourth
obstruction to flow of CSF & internal
Cranial nerves arising from the medulla
this is a congenital deformity
It is an abnormal increase in the volume of
the CSF within the skull.
It occurs due to various reasons:
1. An abnormal increase in the formation of
2. A blockage of circulation of the fluid
3. A diminished absorption of fluid
Communicating vs. Non-communicating
• This is an old
• The terms refer to the
presence or absence of
a communication of the
lateral ventricles with
the spinal subarachnoid
• There is obstruction of CSF flow only within
the ventricular system.There
communication between the ventricular
system and the subarachnoid space. The
commonest cause of this category is
aqueduct blockage or stenosis.
• There is obstruction of CSF flow outwith
the ventricular system. In communicating or
non-obstructive hydrocephalus there is
communication between the ventricular
system and the subarachnoid space. The
commonest cause of this group is postinfectious and post-hemorrhagic
Dandy Walker Syndrome
• A common cause of
hydrocephalus is Dandy
where there is
blockage of foramina of
the 4th ventricle. This
is a congenital condition
agenesis of the
Blockage of CSF resorption
• Poor resorption of CSF
into the venous sinuses
caused by scarring of
the arachnoid villi and
is commonly seen after
Hydrocephalus Ex Vacuo
• Hydrocephalus ex-vacuo
involves the presence of
too much CSF, although the
CSF pressure itself is
• This condition occurs when
there is damage to the
brain caused by stroke or
other form of injury or
and there may be an actual
shrinkage of brain
Normal pressure hydrocephalus
• Normal pressure
hydrocephalus (NPH) is
usually due to a gradual
blockage of the CSF
drainage pathways in the
NPH is an unusual cause of
dementia, which can occur
as a complication of brain
infection or bleeding
Treatment of hydrocephalus
• The two most commonly
used shunt systems are the
ventriculoatrial (VA) and
• The VP shunt is most
commonly used as it is
simpler to place, extra
tubing may be placed in the
peritoneum and the
consequences of infection