BRAIN STEM ANATOMY &
CLINICAL PRESENTATIONS
PROF DR. ÇİĞDEM ÖZKARA
• In vertebrate anatomy the brainstem (or brain
stem) is the posterior part of the brain, adjoining
and structurally continuous with the spinal cord.
• The brain stem provides the main motor and
sensory innervation to the face and neck via the
cranial nerves.
• Though small, this is an extremely important part
of the brain as the nerve connections of the
motor and sensory systems from the main part of
the brain to the rest of the body pass through the
brain stem.
• This includes the corticospinal tract (motor), the
posterior column-medial lemniscus pathway (fine
touch, vibration sensation and proprioception)
and the spinothalamic tract (pain, temperature,
itch and crude touch).
• The brain stem also plays an important role in the
regulation of cardiac and respiratory function. It
also regulates the central nervous system, and is
pivotal in maintaining consciousness and
regulating the sleep cycle.
BRAIN STEM
Includes:
medulla oblongata (myelencephalon),
pons (part of metencephalon),
midbrain (mesencephalon).
Less frequently, parts of the diencephalon are
included.
1.Cerebrum
2.Thalamus
3.Mesencephalon - Midbrain
4.Pons
5.Medulla oblongata
6.Medulla spinalis - Spinal cord
Midbrain (mesencephalon)
The midbrain is divided into three parts.
The first is the tectum, which is "roof" in Latin.
The tectum includes the superior and inferior
colliculi and is the dorsal covering of the
cerebral aqueduct. The inferior colliculus,
involved in the sense of hearing sends its
inferior brachium to the medial geniculate
body of the diencephalon.
Superior to the inferior colliculus, the superior
colliculus marks the rostral midbrain. It is
involved in the special sense of vision and
sends its superior brachium to the lateral
geniculate body of the diencephalon.
The second part is the tegmentum and is
ventral to the cerebral aqueduct.
Several nuclei, tracts and the reticular formation
are contained here.
Last, the ventral side is composed of paired
cerebral peduncles. These transmit axons of
upper motor neurons.
Midbrain
Periaqueductal gray: The area around the cerebral
aqueduct, which contains various neurons involved in
the pain desensitization pathway. Neurons synapse here
and, when stimulated, cause activation of neurons in the
nucleus raphe magnus, which then project down into
the dorsal horn of the spinal cord and prevent pain
sensation transmission.
Occulomotor nerve nucleus: This is the nucleus of CN III.
Trochlear nerve nucleus: This is the nucleus of CN IV.
Red Nucleus: This is a motor nucleus that sends a
descending tract to the lower motor neurons.
Substantia nigra: This is a concentration of neurons in
the ventral portion of the midbrain that uses dopamine
as its neurotransmitter and is involved in both motor
function and emotion. Its dysfunction is implicated in
Parkinson's Disease.
Reticular formation: This is a large area in the midbrain
that is involved in various important functions of the
midbrain. It contains lower motor neurons, is involved in
the pain desensitization pathway, is involved in the
arousal and consciousness systems, and contains the
locus ceruleus, which is involved in intensive alertness
modulation and in autonomic reflexes.
Central tegmental tract: Directly anterior to the floor of
the 4th ventricle, this is a pathway by which many tracts
project up to the cortex and down to the spinal cord.
BEYİN SAPI
• Mezensefalon beyinsapının en üst bölümünü oluşturur. Üçüncü
(N. Oculomotorius) ve IV. (N. Trochlearis) kranyal sinirlerin
nukleusları buradadır
Fibria
Corticospinalis
Substania
Nigra
N.Oculomotorius III
N.oculomotorius(CN3): has 2 nuclei:
 Nüc nervi oculomotorii motor nucleus. At
collikulus superior : All extraoculer mucles
except for M.obliquus superior & m.rectus
lateralis & m.levator palpebra superioris i
were innervated . Upward and internal gaze
 nüc visseralis (edinger westphal):
Parasympathetic nucleus. Innervates M.
sphincter pupillae & M. ciliaris.
Lesion: ptosis , mydriazis, eye down and out
deviation, vertical diplopi , light reflex &
accomodation loss.
N. trochlearis(CN4)
• Only somatomotor .
• M.obliquus superioru
innervation.
• Unique CN leaves brain
stem from posterior
• Lesion: cannot look
down and out , vertikal
diplopi Complains when
coming down the stairs.
• If nucleus n. troclearisin
is damaged: contrlateral
m.obliquus superior is
effected (exception for
other CN)
• Weber sendromu: (superior alternating hemiplegia) is a form of stroke
characterized by the presence of an oculomotor nerve palsy and
contralateral hemiparesis or hemiplegia. It is caused by midbrain infarction
as a result of occlusion of the paramedian branches of the posterior
cerebral artery or of basilar bifurcation perforating arteries.[1]
1. Substantia nigra, akinesia
(parkinsonism)
2. Corticospinal fibers,
contralateral spastic hemiplegia
3. Corticonuclear fibers,
contralateral lower facial and
hypoglossal paralysis,
supranuclear
4. Corticopontine tract,
contralateral dystaxia
5. Root fibers of oculomotor
nerve, ipsilateral oculomotor
paralysis with wide fixed pupil
BENEDIKT SYNDROME: Caused by a lesion ( infarction, hemorrhage, tumor, or
tuberculosis) in the tegmentum of the midbrain and cerebellum. It can result from
occlusion of the posterior cerebral artery
Characterized by the presence of an CN III oculomotor nerve palsy and contralateral
hemiparesis (weakness) and cerebellar ataxia including tremor.
Neuroanatomical structures affected include CNIII nucleus, Red nucleus, corticospinal
tracts, brachium conjunctivum, and cerebellum.
1. Medial lemniscus,
contralateral decrease in
sensations of touch,
position, and vibration
2. Red nucleus,
contralateral hyperkinesia
(chorea, athetosis)
3. Substantia nigra,
contralateral akinesia
(parkinsonism)
4. Root fibers of
oculomotor nerve,
ipsilateral oculomotor
paralysis, wide fixed pupil
Parinaud's Syndrome : results from injury, either direct or
compressive, to the dorsal midbrain. Specifically,
compression or ischemic damage of the mesencephalic
tectum, including the superior colliculus adjacent
oculomotor (origin of cranial nerve III) and Edinger-Westphal
nuclei, causing dysfunction to the motor function of the eye.
A. Pinealoma compressing superior
colliculi and aqueduct.
B. Nuclei of III (IV) and medial longitudinal
tracts are within range of deformation.
1. Cerebral aqueduct, stenosis with occlusive
hydrocephalus
2. Superior colliculi, conjugated upwards gaze
paralysis
3. Oculomotor nucleus, eventual oculomotor
paralysis and ptosis (trochlear paralysis)
4. Medial longitudinal fasciculus, nystagmus
PONS
Named after the Latin word for "bridge" or the
16th-century], It is superior to (up from) the
medulla oblongata, inferior to (down from) the
midbrain, and ventral to (in front of) the
cerebellum.
In humans and other bipeds this means it is above
the medulla, below the midbrain, and anterior
to the cerebellum. This white matter includes
tracts that conduct signals from the cerebrum
down to the cerebellum and medulla, and
tracts that carry the sensory signals up into the
thalamus.
Posteriorly, it consists mainly of two pairs of thick
stalks called cerebellar peduncles. They
connect the cerebellum to the pons and
midbrain.
The pons contains nuclei that relay signals from the
forebrain to the cerebellum, along with nuclei
that deal primarily with sleep, respiration,
swallowing, bladder control, hearing,
equilibrium, taste, eye movement, facial
expressions, facial sensation, and posture.[3]
Within the pons is the pneumotaxic center, a
nucleus in the pons that regulates the change
from inspiration to expiration.[
• Cranial nerves are the abducens nerve VI, facial nerve VII
and the vestibulocochlear nerve VIII, respectively.
• At the level of the midpons, trigeminal nerve V, emerges.
• N. trigeminus(CN5): has 3 sensoriel, 1 motor
nucleus
– nuc. spinalis nervi trigemini: related to cornea
reflex
– Nuc. spinalis nervi trigemini: face and head pain
and temperature sensations 2nd neuron.
– Nuc. mesensefalikus nervi trigemini
– Nuc. motorius nervi trigemini
– Ganglion trigeminale (gasser ganglionu semilunar
ganglion): sensation ganglion
N. Trigeminus branches
• N.ophtalmikus (V1): only sensitive fibres.
Bulbus oculi innervates, tip of nose, upper part
of eyes .
• N.maksillaris(V2): only sensitive fibres , lower part
of eyes, upper lip innervation.
• N.mandibularis(V3) Motor & sensitive fibres.
Masticatory muscles, lower lip and lower part
of mouth , 2/3 anteror part of tongue ,
external ear and temporal region innervation.
• N.abducens(CN6): Only motor fibres.
M.rektus lateralisi innervation. Lesion:
effected eye pulled medially, horizontal
diplopia. Lies in sinus kavernosus lateral to A.
carotis interna
N.facialis(CN7)
• Involves motor, sensory and parasympatic fibres:
nüc.nervi facialis: Motor nuc.Innervates mimic muscles
:m.stapedius,m.stylohyoideus,m.digastrikus venter
posteriorun
Nüc.lacrimalis ve nüc.salivatorius: Parasympathic nuclei
Nüc traktus soliterius:2.neurons of taste
Central facial paralysis: Supranuclear lesions, mouth
commissure deviates to healthy side (lesion), can
close eyes cornea reflex is normal.
Peripheric facial paralysis (Bell’s palsy): Intranuclear
or infranuclear mouth commissure deviates to
healthy side , cornea reflex disappears, cannot close
eye
Millard-Gubler syndrome
It is a syndrome of unilateral
softening of the brain tissue
arising from obstruction of the
blood vessels of the pons.
VI and VII cranial nerves
fibers of the corticospinal tract,
Clinical presentation:
Paralysis of the abducens (including
diplopia, internal strabismus, and loss of
power to rotate the affected eye outward)
facial nerves ( peripheric
ipsilateral)
Contralateral Hemiplegia of the
extremities. It is also known as
"crossed hemiplegia".
1. Medial lemniscus, contralateral
decrease of touch, position and
vibration sensations in the lower
extremities
2. Lateral lemniscus, hypacusia
3. Nucleus of facial nerve, peripheral
ipsilateral paralysis of facial muscles
4. Anterior spinothalamic tract,
contralateral analgesia and
thermanesthesia of body
5. Pyramidal tract, contralateral
spastic hemiplegia
6. Abducent nerve, ipsilateral
peripheral paralysis of lateral rectus
muscle
Peripheral facial paralysis
Central facial paralysis
Kranyal Sinirler (devam)
• N.vestibulocohlearis: N.vestibularis: carries the
informaion related to position and movements of
of head , N.cohlearis: primery audituar fibres.
Medulla oblongata
(bulbus)
is the lower half of the
brainstem.
The medulla contains the
cardiac, respiratory,
vomiting and vasomotor
centers and deals with
autonomic functions, such
as breathing, heart rate
and blood pressure.
Functions
• The medulla oblongata controls autonomic functions,
and relays nerve signals between the brain and spinal
cord.
• It is also responsible for controlling several major
points and autonomic functions of the body:
• respiration– chemoreceptors
• cardiac center – sympathetic, parasympathetic system
• vasomotor center – baroreceptors
• reflex centers of vomiting, coughing, sneezing, and
swallowing
• balancing the human body.
Nuclei of Medulla oblongata
Last five cranial nerve nuclei:
• Nuc. Grasilis ve nuc. kuneatus: second neurons of
conscious proprioceptive, vibration, two point
discrimination sensations
• Nuc. Traktus solitarius: Related to VII,IX,X. cranial nerves.
Upper part is called nuc. Gustatorius and involves neurons
of taste
• Nuc. Spinalis nervi trigemini: Pain and temparature
sensation of face
• Nuc. Ambiguus: motor nuclei of IX,X,XI cranial nerves
• Nuc. Salivatorius inferior: Parasempatik nuclei of XI. CN .
The fibres from this nuclei goes to glandula parotidea
N. Glossofaryngeus(CN9
3 nuclei, 2 ganglions,
Motor: nüc.ambiguus…. İnnervates
m.stylofaringeus
Nüc salivatorius inferior parasempatik
nucleus, innervates glandula parotidea
Nuc traktus solitarius 1/3 posterior of taste
sensation of tongue , tonsilla palatina and
middle ear sense.
Lesion: uvula deviates to healthy side .
The integrity of the glossopharyngeal nerve
may be evaluated by testing the patient's
general sensation and that of taste on the
posterior third of the tongue. The gag
reflex can also be used to evaluate the
glossphyaryngeal nerve
N.vagus(CNX)
3 nuclei, 2 ganglion
Motor nuc: nuc.ambiguus,
Parasympatic nuc: nuc posterior nervi vagi,
Taste : nuc. ractus solitarius
The vagus nerve supplies motor
parasympathetic fibers to all the organs
except the suprarenal (adrenal) glands, from
the neck down to the second segment of
the transverse colon. The vagus also
controls a few skeletal muscles, namely:
• Cricothyroid muscle
• Levator veli palatini muscle
• Salpingopharyngeus muscle
• Palatoglossus muscle
• Palatopharyngeus muscle
• Superior, middle and inferior pharyngeal
constrictors
• Muscles of the larynx (speech).
• This means that the vagus nerve is responsible for such
varied tasks as heart rate, gastrointestinal peristalsis,
sweating, and quite a few muscle movements in the
mouth, including speech (via the recurrent laryngeal
nerve) and keeping the larynx open for breathing (via
action of the posterior cricoarytenoid muscle, the only
abductor of the vocal folds). It also has some afferent
fibers that innervate the inner (canal) portion of the
outer ear, via the Auricular branch (also known as
Alderman's nerve) and part of the meninges. This
explains why a person may cough when tickled on their
ear (such as when trying to remove ear wax with a
cotton swab)
N.accessorius(CNXI)
• Pure motor.
• Some fibres from bulbus some
from servikal m. Spinalis sup.
Segment ant horn cells.
• Leaves cranial cavity from
foramen jugulare very close to
IX. & X. CNs
• The nerve functions to control
the sternocleidomastoid and
trapezius muscles.
N. Hypoglossus (CNXII)
Motor nerve of tongue.
Nucleus in bulbus.
Lesion: tongue deviates
to the paralysed side,
atrophy at that side
Unilateral involment:
No tongue movements
IŞIK REFLEXİ
WALLENBERG’S SYNDROME (lateral medulla syndrome)
It is the clinical manifestation resulting from occlusion of the posterior inferior
cerebellar artery (PICA) or one of its branches or of the vertebral artery, in which the
lateral part of the medulla oblongata infarcts, resulting in a typical pattern.
1. Inferior vestibular nucleus, nystagmus and ipsilateral
inclination to fall
2. Dorsal nucleus of vagus nerve, tachycardia and dyspnea
3. Inferior cerebellar peduncle, ataxia and ipsilateral
asynergia
4. Nucleus of solitary tract, ageusia ipsilateral
5. Ambiguus nucleus, ipsilateral paralysis of palate, larynx,
and pharynx
6. Nucleus of cochlear nerve, hypacusia
7. Nucleus of trigeminal spinal tract, ipsilateral analgesia
and thermanesthesia of face
8. Central sympathetic pathway, Horner's syndrome.
Hypohidrosis, ipsilateral vasodilation in face
9. Anterior spinocerebellar tract, ataxia, ipsilateral
hypotonia
10. Lateral spinothalamic tract, analgesia and
thermanesthesia contralateral over body
Horner sendromu
• Medial medüller syndrome(Dejerine’in anterior medüller sendrom:
Obstruction of a. spinalis anterior veya a. vertebralis
1. Medial longitudinal fasciculus,
nystagmus
2. Medial lemniscus, contralateral
decrease of touch, vibration, and
position sensations
3. Olive, ipsilateral myorhythmia in
velum and pharynx
4. Hypoglossal nerve, ipsilateral flaccid
paralysis of hypoglossal muscle with
atrophy
5. Pyramidal tract, contralateral,
spastic hemiplegia with positive
Babinski reflex
Spinothalamic tract:
pain, tempartature,
itch, crude touch
Posterior column
fine touch, vibration,
conscious
proprioceptive
Cortico spinal tract:
motor
Cranial nerve reflexes
Kranyal Sinirler (devam)