Brain anatomy (part 2)

‫الرحيم‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬,
‫هلل‬ ‫والحمد‬‫العالمين‬ ‫رب‬,
‫أشرف‬ ‫علي‬ ‫والسالم‬ ‫والصالة‬
‫و‬ ‫محمد‬ ‫سيدنا‬ ‫المرسلين‬
‫أجمعين‬ ‫صحبه‬ ‫و‬ ‫اله‬ ‫علي‬

Brain
anatomy
Protective
coverings
Scal
p Bone Meninges
Brain
parenchyma
Cerebrum
Cerebellu
m Brain stem
Cranial
Nerves.
Limbic
system
Vascular
anatomy
Arterial Venous
CSF
spaces
Ventricular system Cisterns

Embryological parts of the brain

3-Brain stem
■ The brainstem is the most caudal part of the brain. It consists of the:
– midbrain (mesencephalon)
– pons (part of the metencephalon)
– Medulla oblongata (myelencephalon)

3-Brain stem
■ The brainstem is the most caudal part of
the brain. It consists of the:
– midbrain (mesencephalon)
– pons (part of the metencephalon)
– Medulla
oblongata (myelencephalon)

A-Midbrain (mesencephalon)
■ When viewed in cross-section, the
midbrain can be divided into three
portions:
■ Tectum= quadrigeminal
plate (posterior) contain 4
colliculi, 2 superior and 2
inferior.
■ Tegmentum (Middle)
■ cerebral
peduncles (anterior)

B-Pons
■ The pons is the middle of the three parts of the brainstem, sitting above the
medulla and below the midbrain. It acts as a relay between the cerebellum and
cerebral hemispheres.

C-Medulla Oblongata
■ The medulla oblongata (or simply medulla) is the most caudal part of
the brainstem and sits between the pons inferiorly and spinal cord superiorly.
■ Pyramids are paired structures located at the medial aspect of ventral medulla.
■ Olives are paired structures located at lateral aspect of ventral medulla, lateral to the
pyramids.
■ The dorsal aspect of the medulla contains the posterior median sulcus (most dorsal
medial sulcus) and more lateral posterolateral sulcus. Between these sulci are the
gracil tract and nucleus at the midline and cuneate tract and nucleus more laterally

4-Cranial nerves
■ The cranial nerves are the 12 paired sets of nerves that arise from
the brain or brainstem and leave the central nervous system through cranial foramina.
■ All have BBB so their enhancement is considered pathologic except the trigeminal
ganglion and labyrinthine segment of the facial nerve.
■ The brainstem nuclei are located within the tegmentum; the posterior section of the
brainstem.
■ The first and second cranial nerves derive from
the telencephalon and diencephalon respectively and are considered extensions of the
central nervous system:
■ olfactory nerve (CN I)
■ optic nerve (CN II)

4-Cranial nerves
■ The third and fourth cranial nerves originate from
the midbrain:
■ Oculomotor nerve (CN III)
■ Trochlear nerve (CN IV)
■ The middle four cranial nerves originate from
the pons:
■ Trigeminal nerve (CN V)
■ Abducens nerve (CN VI)
■ Facial nerve (CN VII)
■ Vestibulocochlear nerve (CN VIII)

4-Cranial nerves
■ The final four cranial nerves originate from
the medulla oblongata:
■ Glossopharyngeal nerve (CN IX)
■ Vagus nerve (CN X)
■ Accessory nerve (CN XI)
■ Hypoglossal nerve (CN XII)

4-Cranial nerves
■ The best imaging modality for CN neuropathy is:
– MSCT
– MRI
– PET
– US

4-Cranial nerves
■ However for each role there is an exception, so that’s
true for all CN neuropathy except distal vagal
neuropathy which need MSCT of the neck and chest
down to aortopulmonary window.

4-Cranial nerves
■ The best sequence for depiction of the cranial nerves
and its pathology is SSFP (scientific name) and has
trade names of constructive interference steady state
b-FFE (Philips), fast imaging employing steady-state
acquisition FIESTA (GE) and Fast Imaging with
steady State Precession FISP (Siemens).

4-Cranial nerves
CN I-Olfactory Nerve.
■ The olfactory nerve consists of
a collection of sensory nerve
fibers (the olfactory filiae).
■ The olfactory filiae enter the
anterior cranial fossa via the
cribriform plate of the ethmoid
bone
■ Terminate in the olfactory
bulbs, which lie in bony
grooves formed by the
cribriform plate.
1, olfactory bulb.

4-Cranial nerves
■ The olfactory bulbs’ axons
leave it in the olfactory tract,
which runs inferior to the
olfactory sulcus.
2, olfactory tract; 3, olfactory sulcus; 4, medial
orbitofrontal gyrus; 5, gyrus rectus.

4-Cranial nerves
■ The olfactory bulbs’ axons
leave it in the olfactory tract,
which runs inferior to the
olfactory sulcus.

4-Cranial nerves
CN II-Optic Nerve.
■ The optic nerve emerges from the
posterior pole of the eye globe,
■ leaves the orbit via the optic canal
to reach the anterior cranial fossa.
■ Both optic nerves join to form the
optic chiasm within the suprasellar
cistern.
■ At the chiasm the nasal fibers of
each optic nerve cross the midline
(decussate) to join with the
uncrossed temporal fibers of the
opposite optic nerve, forming the
optic tracts.
1, optic nerve; 2, optic chiasm; 3, optic tract; 4,
lateral geniculate body.

4-Cranial nerves
CN II-Optic Nerve.
■ From the optic chiasm, the paired
optic tracts curve posteriorly
around the cerebral peduncles to
terminate in the lateral geniculate
bodies
■ From the lateral geniculate bodies
the optic radiations curve toward
the primary visual cortices at the
medial aspect of the occipital
lobes, along the calcarine sulcus. 1, superior colliculus; 2, red nucleus; 3, substantia nigra; 4,
cerebral peduncle; 5, mammillary body; 6, fornix; 7, optic
chiasm; 8, optic nerve; 9, Oculomotor nerve; 10,
interpeduncular fossa; 11, posterior cerebral artery; 12,
cerebral aqueduct.

4-Cranial nerves
CN III-Oculomotor Nerve.
■ The nucleus of the third nerve is
located in the midbrain at the
level of the superior colliculi.
■ The fascicles of CN III curve
ventrally through the midbrain and
exit the brain stem along the
ventromedial aspect of the
cerebral peduncle within the
interpeduncular fossa

4-Cranial nerves
■ then courses through the
interpeduncular and passing
between the P1 segment of the
posterior cerebral artery (PCA)
above and the superior cerebellar
artery (SCA) below.

4-Cranial nerves
■ Then enters the lateral dural wall
of the cavernous sinus and
courses superiorly and laterally
within it.
■ Then enter the orbital cavity via
the superior orbital fissure within
annulus of Zinn.
1, oculomotor nerve; 2, trochlear nerve; 3, Abducent nerve; 4,
ophthalmic nerve; 5, maxillary nerve; 6, optic nerve; 7, internal
cerebral artery, cavernous segment; 8, optic chiasm; 9, pituitary
gland.

4-Cranial nerves
CN IV Trochlear nerve.
■ The nucleus of CN IV is located in the
midbrain at the level of the inferior
colliculus
■ The nerve fascicles pass posteriorly
within the periaqueductal gray matter
and then decussate within the superior
medullary velum before emerging at
the dorsal surface of the midbrain just
inferior to the contralateral inferior
colliculus
■ CN IV is the sole cranial nerve to exit
the brain stem dorsally and on the
side opposite its nucleus.

4-Cranial nerves
■ CN IV then courses ventrally and
laterally through the
quadrigeminal and ambient
cisterns.
■ The trochlear nerve enters the
cavernous sinus and passes
anteriorly in the lateral dural wall
of the cavernous sinus, inferior to
the third nerve and superior to the
ophthalmic division of the fifth
cranial nerve.
1, Oculomotor nerve; 2, trochlear nerve; 3, Abducent nerve;
4, ophthalmic nerve; 5, maxillary nerve; 6, optic nerve; 7,
internal cerebral artery, cavernous segment; 8, optic chiasm;
9, pituitary gland.

4-Cranial nerves
■ After passing the cavernous
sinus, it enters the orbital apex via
the superior orbital fissure
external to the annulus of Zinn to
innervate the contralateral
superior oblique muscle.
1, inferior colliculus; 2, cerebral aqueduct; 3, cerebral peduncle; 4,
posterior cerebral artery; 5, posterior communicating artery; 6,
quadrigeminal cistern; 7, superior medullary velum; 8, ambient
cistern.

4-Cranial nerves
CN V Trigeminal nerve.
■ The largest cranial nerve.
■ There are 4 nuclei which span from
the midbrain through
the pons and medulla and into the
upper cervical cord.
■ The trigeminal nerve exits at the
mid pons,
■ courses through the prepontine
cistern to enter Meckel's cave
where its fibers form the trigeminal
= Gasserian = semilunar ganglion.
It then divides into three main
branches

4-Cranial nerves
Ophthalmic division (V1)
■ Courses anteriorly in the lateral wall
of the cavernous sinus inferior
to trochlear nerve.
■ Entering the orbit through superior
orbital fissure.

4-Cranial nerves
Maxillary division (V2)
■ Courses anteriorly low in the lateral wall of the
cavernous sinus inferior to trochlear nerve.
■ Exiting the skull through the foramen
rotunda in the greater wing of the sphenoid
bone to enter the pterygopalatine fossa.

4-Cranial nerves
Mandibular division (V3)
■ Courses inferiorly through the foramen
ovale to exit the skull. It hence does not
course through the cavernous sinus.

4-Cranial nerves
CN VI Abducent nerve.
■ Its nucleus located in the dorsal pons beneath
the colliculus of the facial nerve in the
Rhomboid fossa (floor of the 4th ventricle).
■ Emerging from anterior aspect of the Pons at
pontomedullary junction nearly at the same
level of CN VII & VIII.

4-Cranial nerves
■ Run horizontally in the prepontine cistern in
posterior to anterior direction.
■ The ascends vertically on the back of clivus in
fibrous canal called Dorello canal.

4-Cranial nerves
■ Continues over the petrous apex and through
the medial cavernous sinus, entering the orbit
through the superior orbital fissure to
innervate the lateral rectus muscle.

4-Cranial nerves
CN VII Facial nerve.
■ Facial nerve nucleus occurs in the pons and its
fibers loop posteriorly over the abducens
nerve nucleus to form the facial colliculus in the
floor of fourth ventricle.
1-Intracranial (cisternal) segment
– The nerve emerges from lateral aspect of the
Pons medial to the vestibulocochlear nerve.
Together the two travel laterally through
the cerebellopontine angle to the internal
acoustic meatus.
– The cisternal segment has no branches.

4-Cranial nerves
2-Meatal (canalicular) segment
– Located in the anterior superior quadrant
of the internal auditory canal, above
the falciform crest and anterior to Bill's
bar.
– The meatal segment has no branches.

4-Cranial nerves
3-Labyrinthine segment
– The facial nerve enters the Fallopian canal, passing anterolaterally between and
the cochlea (anterior) and vestibule (posterior),
– and then bends posteriorly at the geniculate ganglion
– It has three branches.

4-Cranial nerves
4-Mastoid segment
■ Extends from the posterior genu to the stylomastoid foramen,
■ It gives off three branches

4-Cranial nerves
5-Extra-temporal segment
As the nerve exits the stylomastoid foramen, it
enters the parotid gland lying between the deep
and superficial lobes of the gland and emerging
from the anterior border of the gland

4-Cranial nerves
■ CN VIII Vestibulocochlear nerve.
– It emerges between the pons and the medulla, lateral to the facial nerve
– Passing laterally through the cerebellopontine angle to the internal acoustic
meatus (IAM) with the aforementioned nerve.
– In the IAM the nerve splits into 3 bundles: cochlear nerve, superior and
inferior division of the vestibular nerve.

4-Cranial nerves
■ CN IX Glossopharyngeal.
– It exits the medulla oblongata from
the postolivary sulcus, the
glossopharyngeal nerve passes
laterally anterior to the flocculus at
the lateral cerebellomedullary
cistern, above the vagus nerve.
– and leaves the skull through
the pars nervosa of the jugular
foramen

4-Cranial nerves
■ CN X Vagus.
– The vagus nerve comprises two
roots that emerge from the side of
the medulla at postolivary sulcus.
– Then enter the cerebellomedullary
cistern in a position inferior to the
glossopharyngeal nerve and run
parallel to it through the cistern.
– Because of their parallel course, it
may be difficult to distinguish
between the glossopharyngeal and
vagus nerves on axial FIESTA
images; coronal or oblique coronal
views along the course of the
nerves are best for that purpose.

4-Cranial nerves
■ CN X Vagus.
– After obliquely traversing the
lateral cerebellomedullary
cistern, the vagus nerve
enters the jugular fossa and
exits the skull through the
jugular foramen, between
the glossopharyngeal and
accessory nerves.

4-Cranial nerves
■ CN XI accessory.
– The accessory nerve is composed of
multiple cranial and spinal rootlets.
– The cranial rootlets emerge into the
lateral cerebellomedullary cistern
below the vagus nerve.
– The spinal rootlets emerge from upper
cervical segments of the spinal cord.

4-Cranial nerves
■ CN XI accessory.
– After leaving the spinal cord, the spinal rootlets pass superiorly
through the foramen magnum into the cisterna magna and join the
cranial rootlets in the lateral cerebellomedullary cistern.
– The conjoined nerve fibers then leave the skull through the jugular
foramen, posterior to the glossopharyngeal and vagus nerves.

4-Cranial nerves
■ CN XII Hypoglossal.
o The hypoglossal nerve emerges as a
series of rootlets extending from the
pre olivary sulcus of the medulla into
the lateral cerebellomedullary cistern .
o The combined rootlets then cross the
lateral cerebellomedullary cistern,
where the nerve is surrounded
anteriorly by the vertebral artery and
posteriorly by the posterior inferior
cerebellar artery.
o The hypoglossal nerve then exits the skull
via the hypoglossal canal, which runs
obliquely in the axial plane.

Limbic system is made of two
portions:-
1-Limbic lobe made of:-
– Hippocampus.
– Para hippocampal gyrus.
– Cingulate Gyrus.
– Subcallosal gyrus
2-Subcortical nuclei made
of:-
– Amygdala.
– Septal nuclei.
– Hypothalamic nuclei.
– Some thalamic nuclei.

Hippocampus
■ Curved structure on the medial aspect of
temporal lobe that bulges into floor of
temporal horn.
■ Consists of three structures forming two
interlocking U shaped structure:
– Hippocampus proper( Ammon’s
horn)
Superolateral.
– Dentate gyrus
Inferomedial U
– Subiculum

Hippocampus proper (Ammon’s horn)
Head ( Pes hippocampus )
■ Most anterior part, oriented transversely,
landmarked by basilar
artery to interpeduncular cistern.
■ 3 – 4 digitations on superior surface.
Body
■ Swiss roll shape, adjacent to brain stem.
■ The white matter tracts of the alveus and
fimbria are superior to it.
Tail
■ Most posterior, narrows then curves
around splenium to form indusium griseum
above cc.

Hippocampus proper (Ammon’s horn)
Surrounded with the following CSF
spaces:-
1. Temporal horn of lateral ventricle
laterally with its medial extension
choroidal fissure and uncal recess.
2. Ambient cistern medially separating
its from brain stem.
3. Hippocampal sulcus.
4. Collateral sulcus.

Amygdala
■ Amygdala lies anterior &superior
to hippocampus, at medial aspect
of temporal lobe.
■ Tail of caudate nucleus ends in
amygdala.
Hippocampal head lies just
posterior to amygdala.

‫إله‬ ‫ال‬ ‫أن‬ ‫أشهد‬ ‫بحمدك‬ ‫و‬ ‫اللهم‬ ‫سيحانك‬
‫أليك‬ ‫أتوب‬ ‫و‬ ‫أستغفرك‬ ‫أنت‬ ‫إال‬

Brain anatomy (part 2)

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