CLOSED MEDULLA (MOTOR
DECUSSATION)
The medulla is traversed 
by the central canal.
It retains some of the 
features of the spinal cord.
HORNS
The ventral horn becomes 
much attenuated.
The dorsal horn is replaced 
by
The caudal part of the 
Trigeminal Sensory Nucleus
(Nucleus of the Spinal Tract
of the Trigeminal Nerve).
It is a large nucleus that lies 
medial to the spinal tract of
the trigeminal nerve.
The TRIGEMINAL SENSORY
NUCLEUS
It is the brain stem 
continuation of the Substantia
Gelatinosa of the dorsal horn
of the spinal cord.
It extends through the whole 
length of the brain stem.
It receives pain and 
temperature from the face,
forehead and the mucous
membrane of the mouth and
nose.
SPINAL TRACT OF THE
TRIGEMINAL NERVE
It lies superficial to its 
nucleus between the
cuneate nucleus and the
spino-cerebellar tracts.
It is formed of descending 
fibers that terminate in
the trigeminal nucleus
caudal to the level of the
pons (where the
trigeminal nerve is
attached).
PYRAMIDAL DECUSSATION
(MOTOR DECUSSATION)
It is the distinguishing 
feature of this level.
75-90% of the 
pyramidal fibers ( cortico
spinal) cross to the
opposite side and
descend in the lateral
white column of the
spinal cord as the Lateral
Corticospinal tract.
LATERAL & ANTERIOR WHITE
COLUMNS
Spinocerebellar 
and Spino thalamic
tracts can be
identified.
GRACILE & CUNEATE NUCLEI
A small part of these 
nuclei lie deeper to
their corresponding
Gracile and Cuneate
tracts.
MID MEDULLA (SENSORY
DECUSSATION)
It is still traversed 
by the central
canal.
THE GRACILE & CUNEATE
NUCLEI
They are Large in size 
and located deeper to
their corresponding
tracts.
Their axons will form 
the internal arcuate
fibers.
They cross the median 
plane forming with the
opposite side the
Sensory Decussation.
MEDIAL LEMINISCUS
It is a distinct tract which is 
formed from the crossed
sensory fibers.
It ascends through the rostral 
medulla, pons and midbrain.
It lies adjacent to the middle 
line and ventral to the central
canal.
It terminates in the thalamus. 
PYRAMIDS
Are prominent above their
decussation.
They are present in the
antero medial part of the
section.
ARCUATE NUCLEI
They lie antero lateral to 
the pyramids.
Their axons form the 
External Arcuate Fibers.
The nuclei can be 
considered as the inferior
extension of the pontine
nuclei.
Their fibers reach the 
cerebellum through the
inferior cerebellar
peduncle.
RETICULAR FORMATION
It is in the form of a 
diffuse mixture of
nerve fibers and small
groups of nerve cells
which are located
posterolateral to the
pyramids and ventral
to the spinal tract and
nucleus of the
trigeminal nerve.
ACESSORY CUNATE NUCLEUS
It is lateral to the cuneate 
nucleus.
It receives unconscious 
fibers from the cervical
region. The cell axons
reach the cerebellum
through the inferior
cerebellar peduncle.
THE OPEN (ROSTRAL)
MEDULLA
The posterior surface of 
the medulla here forms
the lower part of the floor
of the 4th ventricle.
MEDIAL LEMINISCUS
It is dorsal to the 
medial aspect of the
pyramids on each side
of the midline.
INFERIOR OLIVARY NUCLEUS
It is a convoluted mass of 
gray matter with its hilum
directed medially.
It lies postero lateral to the 
pyramid and lateral to the
medial leminiscus.
It receives fibers from (motor 
and sensory cortices of the
cerebral cortex, red nucleus
of the mid brain and the
corpus striatum).
It is concerned with the 
control of movement.
INFERIOR CEREBELLAR
PEDUNCLE (RESTIFORM
BODY)
It lies in the dorso lateral part 
of the medulla.
It forms the connection 
between the medulla and
cerebellum.
Among the fibers it carries are 
the olivocerebellar,
vestibulocerebellar and dorsal
spinocerebellar from the
limbs.
COCHLEAR NUCLEI
Dorsal and Ventral 
Nuclei:
They lie dorsal and 
lateral to the inferior
cerebellar peduncle.
They receive afferents 
from the cochlear
nerve.
NUCLEI BENEATH THE FLOOR
OF THE 4TH VENTRICLE
Hypoglossal nucleus : 
It forms a longtudinal 
column just lateral to
the midline and
immediately beneath
the floor of the fourth
ventricle.
NUCLEI BENEATH THE FLOOR
OF THE 4TH VENTRICLE
Dorsal motor nucleus 
of the vagus:
It is lateral to the 
hypoglossal nucleus .
It contains the 
preganglionic
parasympathetic fibers
that pass through the
vagus nerve as far as
the distal one third of
the transverse colon.
NUCLEI BENEATH THE FLOOR
OF THE 4TH VENTRICLE
Vestibular nuclei (Complex): 
They lie in the lateral part of 
the floor of the 4th ventricle
and receive afferents from
the vestibular nerve.
They consist of medial, 
lateral, inferior and superior
nuclei.
The inferior vestibular 
nucleus is lateral to the
inferior fovea.
NUCLEUS AMBIGUUS
It lies dorsal to the 
inferior olivary nucleus.
It sends motor fibers to 
the constrictor muscles of
the pharynx and intrinsic
muscles of the larynx
through the
glossopharyngeal, vagus
and cranial part of
acessory nerve.
MEDIAL LONGTUDINAL
BUNDLE
It lies ventromedial to the 
hypoglossal nucleus,
dorsal to the medial
lemniscus and close to the
midline.
It can be identified in the 
pons, midbrain and upper
levels of the spinal cord.
It receives afferents from 
the vestibular nerve.
MEDIAL LONGTUDINAL
BUNDLE
It consists of short 
ascending and descending
fibers that connect the
vestibular and cochlear
nuclei with the cranial
nuclei (111, 1v and v1)
which supplies the extra
ocular muscles. It serves
the coordination of head
and eye movements in
response to vestibulocochlear stimuli.
SPINAL LEMINISCUS
It includes the 
Spinothalamic (lateral
&anterior) and the
Trigeminothalamic tracts
which are very close to
one another.
It is deeply placed lateral 
to the medial leminiscus
and dorsal to the inferior
olivary nucleus.
AREA POSTREMA
It is the most caudal 
point of the floor of the
4th ventricle.
It is the site of action of 
the centrally acting
emetics.
Because at this site, the 
blood brain barrier is
lost for certain
chemicals.
NUCLEUS SOLITARIS
It is formed of medial part 
(well formed in the medulla)
and lateral part (well formed
in the pons) .
The solitary tract lies in 
between.
The lateral nucleus receives 
taste fibers from the back of
the tongue.
The medial nucleus receives 
(GVA) fibers.
RETICULAR FORMATION
It consists of a diffuse 
mixture of nerve
fibers and small
groups of nerve
cells.it is deeply
placed posterior to
the olivary nucleus.
At this level of the 
medulla, it represents
a small part of this
system.
DESCENDINGTRACTS
The Pyramids at the 
anterior part.
Tectospinal tract dorsal to 
the medial lemniscus.

ASCENDING TRACTS
Medial leminiscus. 
Spinal leminiscus.
Trigemino thalamic
tract.
Ventral 
spinocerebellar tract.
MEDULLARY SYNDROMES
Medial Medullary Syndrome
It is due to thrombosis 
of branches of the
anterior spinal artery.
It is manifested by : 
(1) Contralateral 
hemiplegia of the flaccid
type (due to involvement
of the pyramidal fibers
only).
Medial Medullary Syndrome
(2) Contralateral loss 
of proprioceptive
sensation and fine
touch (affection of
medial lemniscus).
(3) Ipsilateral lower 
motor lesion of the
hypoglossal nerve
(affection of
hypoglossal nucleus).
Lateral Medullary
(Wallenberg) Syndrome
It is due to 
thrombosis of the
inferior cerebellar
artery.
It is Manifested by 
(1) Ipsilateral 
cerebellar ataxia (
affection of
cerebellum and
spinocerebellar
tracts).
Lateral Medullary
(Wallenberg) Syndrome
2) loss of pain and 
temperature of the
ipsilateral half of the
face ( spinal tract and
nucleus of V nerve).
(3) loss of pain and 
temperature from the
contralateral half of
the body (spinal
lemniscus).
Lateral Medullary
(Wallenberg) Syndrome
(4) Ipsilateral

paralysis of the
muscles of the palate,
pharynx and larynx
(nucleus ambiguus ).
(5) Ipsilateral loss of 
taste from the
posterior third of the
tongue (nucleus
solitaris).
Lateral Medullary
(Wallenberg) Syndrome
(6) Ipsilateral 
Horner’s syndrome
(ptosis, myosis,
anhydrosis and
enophthalmos ) due
to affection of
descending
autonomic fibers.