RADIOLOGIC
ANATOMY OF THE
BRAIN
Assistant professor
Dr. Haider Najim Aubaid
F.B.M.S., D.M.R.D
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MRI
Vs
CT
Brain CT…
 You have to recognize the following:
1. Cerebral hemispheres
2. Basal ganglia and thalamus
3. Meningies
4. Brainstem
5. cerebellum
6. Ventricular system
7. Basal cisterns (subarachnoid space)
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-The Sylvain cistern and fissure separating the
frontal and temporal lobes are easily identified
on axial CT or MR slices
-The central sulcus
•between the frontal and parietal lobes.
•less well seen, lies just posterior to the anterior limit of
the lateral ventricles.
•on upper images the central sulcus is quite posterior in
position.
The parieto-occipital sulcus on the medial surface of the hemisphere can be
seen on CT at the level of the lateral ventricles and on midline sagittal MR
images
The parieto-occipital junction on the lateral surface has no anatomical landmark
but lies at approximately the same level as the sulcus.
Midline sagittal images also show the cingulate gyrus and callosal and cingulate
sulci.
Insula
•This is the cortex buried in the floor of the lateral sulcus.
•The parts of the frontal, parietal and temporal lobes that
overlie the insula are called the operculum
Corona radiata
& Centrum semiovale
Axial cross-sections of the brain, above the corpus callosum,
show a mass of WM on each hemisphere referred to as
"centrum semiovale".
Below it, projection fibers arising from the cortex and directed
towards the internal capsule, together with fibers ascending from
below towards the cortex, form the "corona radiata“ within
space on each side of the bodies of the lateral ventricles
Basal ganglia
oThe corpus striatum –
othe caudate and
olentiform nuclei
oThe amygdaloid body; and
oThe claustrum.
Caudate nucleus
•head, body and tail.
•It is curved and lies within the concavity of the lateral
ventricle.
Thus :
•head projects into the floor of the anterior (frontal horn)
•body lies along the body of the lateral ventricle.
•tail lies in the roof of the inferior (temporal) horn.
Note:
•The head of the caudate nucleus is usually more
radiodense than the lentiform nucleus or the thalamus
Lentiform nucleus
•biconcave lens.
•Larger lateral putamen
•smaller medial globus pallidus.
•Medially, it is separated from the
•head of the caudate nucleus anteriorly,
•thalamus posteriorly by the internal capsule
Claustrum
•thin sheet of grey matter lies between the putamen and
the insula.
•separated medially from the putamen by the external
capsule and
•bounded laterally by (the extreme capsule) just deep to
the insula
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The corpus callosum
•large midline mass of commissural fibers, which connects
corresponding areas of both hemispheres.
•It is approximately 10 cm long and becomes progressively thicker
towards its posterior end.
NOTE:
•The corpus callosum cannot be well seen on axial CT slices.
•The rostrum, genu, body and splenium can be seen on
sagittal MRI
•Named parts include the:
• Rostrum - this is the first part,
• Genu - most anterior part;
• Trunk (body) -. lies below the
lower free edge of the falx cerebri.
• Splenium - thickened posterior
end.
Meningies
Pineal gland
The pineal gland lies between the posterior ends of the thalami ,
below splenium above and the superior colliculi. within 3 mm of
the midline.
Calcification…normal?...abnormal?
-measuring
• 5–6 mm in length,
• 3–6 mm in width and
• 3–5 mm in height
It does not have a blood–brain barrier
and therefore normally enhances after
IV contrast.
Hypothalamus
forms the floor of the 3rd vent.
Best be appreciated on midline
sagittal MRI
It includes the following, starting
anteriorly:
Optic chiasm;
Tuber cinereum - a sheet of grey matter
Infundibular stalk - leading down to the
posterior lobe of the pituitary gland;
Mamillary bodies - small round masses
Posterior perforated substance.
LEFT: Normal infundibular recess of the third ventricle
(blue arrow) , mamillary bodies (red arrow)
RIGHT: Tuber cinereum hamartoma (curved arrow
PITUITARY GLAND
Relations :
• Above: the diaphragma sella (dura mater) and above
this the suprasellar cistern with the optic chiasm anteriorly
and the circle of Willis;
• Below: the body of sphenoid and the sphenoid sinus; and
• Laterally: the dura and the cavernous sinus and its
contents, (ICA and abducent n.) with oculomotor, ophthalmic and trochlear
nerves in its walls.
Intercavernous sinuses, surround the pituitary gland
anteriorly, posteriorly and inferiorly.
Notes
-Pituitary has high signal intensity on unenhanced
T1 W images.
-The dura above the sella should be horizontal,
not convex?
Exceptions?.
-The diameter of the infundibulum ..??
THE BRAINSTEM
Midbrain
Cisterns:
1-Interpeduncular cistern (5) lies anteriorly
between cerebral peduncles.
2-Qaderigeminal cistern: (4) lies posterior to
quadrigeminal plate
Posterior surface of the midbrain presents four
rounded prominences - the superior and
inferior colliculi (qadri-)
Part of the midbrain posterior to the aqueduct
is called the tectum or quadrigeminal plate.
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4
Midbrain
Nerves:
The third (III oculomotor) N. emerges from between the cerebral peduncles
anteriorly
The fourth (IV trochlear) N. emerges from the dorsal surface
It is not always possible to identify the cerebral aqueduct.
Pons
the widest part of the brainstem.
Basilar artery may be seen anterior to the
pons, position to the right or left of the
midline is not abnormal.
Pons
Cranial nerves:
Fifth (V facial) N. emerges from the anterolateral surface
The sixth (VI abducent) N.: junction with the medulla, close to the
midline anteriorly.
The seventh and eighth (VII and VIII) cranial nerves : junction
with the medulla laterally, that is, (at the CPA)
Medulla oblongata
Cranial nerves:
Ninth and tenth (IX and X glossopharyngeal & vagus) s: posterior
to the olive.
Eleventh (XI) accessory N. has medullary rootlets that arise inferior
to those of X.
(note: cervical rootlets arise from the upper spinal cord and enter the
foramen magnum to unite with the medullary roots).
Twelfth (XII hypoglossal) cranial nerve :anterior to the olive
.
CEREBELLUM
-two hemispheres with the midline vermis between
-has a cortex of grey matter and deeper white matter.
-The surface of the cerebellum has sulci & folia.
Coronal
Axial
-There are deep nuclei within the
hemispheres, the largest of is the dentate
nucleus.
-Tonsils are the most anterior inferior part of
and lie close to the midline.
the hemispheres
-Three cerebellar peduncles:
1-superior  midbrain
2-middle  Pons
3- inferior  Medulla oblongata
The superior surface of the cerebellum slopes upwards from posterior to
anterior
CT slice of upper cerebellum, contains cerebellum anteriorly and
occipital lobes posterolaterally..
Vermis is the narrow midline portion of the cerebellum.
Lingula, is the most anterior part of the superior vermis (lying on the
superior medullary velum).
Nodule, the most inferior part of the vermis
Superior vermis can be
seen between the occipital
lobes on sections through
the thalamus
VENTRICLES, CISTERNS
The ventricles are lined with ependyma, which is
invaginated by plexuses of blood vessels called the choroid
plexus.
These vessels produce the CSF.
The ventricular system is continuous with the central
canal of the cord & also with the subarachnoid space
around the brain via foramina in the fourth ventricle
CSF circulation
The lateral ventricles
Each is C-shaped, with the limbs of the C facing anteriorly and a
posterior extension from its midpoint.
Each one has a
frontal (anterior) horn,
a body (atrium),
a temporal (inferior) horn
occipital (posterior) horn.
Interventricular foramen (of Monro) at the junction of the anterior
horn and the body connects each lateral ventricle with the third
ventricle
Frontal:
Its roof and anterior extremity are formed by the corpus
callosum,
The head of the caudate nucleus makes a prominent
impression
There is no choroid plexus in the anterior horn into the
frontal lobe.
SEPTUM
PELLUCIDUM
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Body
This is within the parietal lobe.
Thalamus lies in the floor medially, with the body of the
caudate nucleus laterally and the thalamostriate groove and
vein between
Temporal (inferior) horn
Caudate nucleus tail lies in the roof of the inferior horn.
Hippocampus forms the floor of the inferior horn.
are small or not visible unless they are dilated
Occipital horn
arises from the posterior convexity of the body which is
called the trigone.
The occipital horn may be absent or poorly developed, or
may extend the full depth of the lobe.
Often asymmetrical .
If the posterior horn is present on one side only it is
usually the left.
There is no choroid plexus in the occipital horn
Third ventricle
slit-like space between the thalami.
Its width is between 2 and 10 mm
and increases with age.
lateral walls  the thalami.
floor  structures of hypothalamus.
The thalami are connected across the ventricle in 60% of
subjects by a non-neural connection, the massa intermedia
or interthalamic adhesion.
Cerebral aqueduct
Narrow channel connecting the
posterior end of the 3rd vent. with the
superior end of the 4th vent..
Measures1. 5 cm in length and 1-2
mm in diameter,
Passes through the brainstem with
the tectum (the quadrigeminal plate)
posterior to it and the tegmentum
and cerebral peduncles anteriorly
Fourth ventricle
floor is diamond-shaped (the rhomboid fossa) and is formed by
the posterior surface of the pons and of the upper part of the
medulla.
roof is formed:
superiorly by the superior cerebellar peduncles, with the
superior medullary velum between,
and inferiorly by the inferior cerebellar peduncles and the
inferior medullary velum.
Over these lies the cerebellum .
Fourth ventricle
Three openings are present in the lower part of the roof :
Single Median aperture (of Magendie) which communicates
with the cisterna magna.
Two Lateral apertures (of Luschka) at the apex of lateral
recesses (lateral prolongation of cavity of the 4th vent. on each side )
and open anteriorly into the pontine cistern
NOTE:
4th & 3rd ventricles and the aqueduct tend to be
symmetrical in its anatomy and minor asymmetry
may be a sign of pathology
Interesting!!
The Rt. and Lt. sided dominance is anatomically expressed by a mild
hemispheric hypertrophy that is at its most in the occipital region:
In such cases, the left occipital lobe, extends slightly farther back than the
right one, sometimes scalloping the occipital bone, sometimes bulging on
the midline.
The left occipital horn is usually longer than the contralateral, and the left
transverse venous sinus is lower and smaller than the right one in about
50% of individuals
The coronal T2WI and FLAIR images show right-sided mesial temporal sclerosis.
Notice the volume loss, which indicates atrophy and causes secondary enlargement
of the temporal horn of the lateral ventricle.
The high signal in the hippocamous reflects gliosis.
vertebral artery
and its PI cerebellar branch.
2-Pontine (pre-pontine
4-Quadrigeminal (cistern of the great vein)
Ambient cisterns (yellow arrow)
1-suprasellar cisterns
confluence of the internal cerebral veins and
the basal veins to form the vein of Galen
Posterior cerebral artery and the basal vein
optic nerves, anterior part of the circle of Willis
Major venous sinuses