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PONS and MEDULLA
PONS and MEDULLA
Pons
cerebellum
cerebral peduncle of midbrain
medulla
middle cerebellar peduncle
basilar groove
motor root of trigeminal
sensory root of trigeminal 6
7 8
transverse fibers
median sulcus
middle cerebellar peduncle
inferior cerebellar peduncle
superior cerebellar peduncle
sulcus limitans
medial eminence
facial colliculus
vestibular area
substantia ferruginea
midbrain
pons
medulla
Internal structures of the pons
1. Transverse section through the cranial part passing
through the trigeminal nuclei 2. Transverse section through the caudal part passing
through the facial colliculus
Transverse section through the pons at the level of the trigeminal nuclei
medial lemniscus
cavity of fourth ventricle
motor nucleus of trigeminal nerve
main sensory nucleus of trigeminal nerve
reticular formation
trapezoid body
spinal lemniscus
Bundles of corticospinal and corticonuclear fibers
pontine nuclei
transverse fibers
Transverse section of the pons at the level of the facial colliculus
medial lemniscus
nucleus of facial nerve
nucleus of abducent
facial colliculus
trapezoid body
inferior cerebellar peduncle
pontine nuclei
Bundles of corticospinal and corticonuclear fibers
medial longitudinal fasciculus
transverse pontine fibers
middle cerebellar peduncle
medial vestibular n.
Blood supply to the pons
The pons is supplied by the basilar artery through its branches: 1. pontine arteries 2. anterior inferior cerebellar artery 3. superior cerebellar artery
medulla
Medulla
Gross appearance of the medulla oblongata
anterior median fissure
pyramid
olives
hypoglossal nerve
pons
decussation of the pyramids
(10)
(11)
(9)
Posterior view of the medulla
central canal
inferior cerebellar peduncle
floor of the fourth ventricle
central canal
fourth ventricle
Posterior view of the medulla
posterior median sulcus
gracile tubercle
cuneate tubercle
Internal structures of the medulla
1. Level of Decussation of pyramid
2. Level of Decussation of Lemnisci
3. Level of the olives
4. Level just inferior to the pons
Transverse section of the medulla
level of decussation of the pyramid
anterior median fissure
posterior median sulcus
posterior spinocerebellar tract
anterior spinocerebellartract
lateral spinothalamic tract
corticospinal tract
decussation of the pyramids
level of decussation of the pyramid
anterior median fissure
posterior median sulcus fasciculus gracilis
nucleus gracilis
fasciculus cuneatus
nucleus cuneatus
spinal nucleus of trigeminal nerve
central canal
Transverse section at the level of Decussation of Lemnisci
pyramid
nucleus gracilis
nucleus cuneatus
internal arcuate fibers
spinal nucleus of trigeminal nerve
posterior spinocerebellar tract
anterior spinocerebellar tract
lateral spinothalamic tract decussation of medial lemnisci
Transverse section at the level of Decussation of Lemnisci
pyramid
nucleus gracilis
nucleus cuneatus
spinal nucleus of trigeminal nerve
decussation of medial lemnisci
hypoglossal nucleus
spinal root of accessory nerve
pyramids medial lemniscus
Transverse section at the level of the olives
reticular formation
tectospinal tract
medial longitudinal fasciculus
olives
hypoglossal nerve
anterior median fissure
inferior cerebellar peduncle
dorsal accesory olivary nucleus
inferior olivary nucleus
medial accesory olivary nucleus
inferior vestibular nucleus
medial vestibular nuclei
posterior cochlear nucleus
Transverse section at the level of the olives
anterior cochlear nucleus nucleus ambiguus
dorsal vagal nucleus
arcuate nuclei
nucleus of tractus solitarius
1. The olivary nuclear complex: a. inferior olivary nucleus b. medial accessory olivary nucleus c. dorsal accessory olivary nucleus. . 2. Vestibular nuclear complex: a. medial vestibular b. inferior vestibular c. lateral vestibular d. superior vestibular 3. Cochlear nuclei: the anterior and posterior 4. Nucleus ambiguus 5. Nucleus of tractus solitarius 6. Dorsal nucleus of the vagus 7. Hypoglossal nuclei 8. Arcuate nuclei
pyramid
inferior cerebellar pedunclereticular formation
medial lemniscus
Transverse section just inferior to the pons
lateral vestibular nucleus
posterior cochlearnucleus
anterior cochlear nucleus
Blood supply to the medulla
The medulla oblongata is supplied by the *Vertebral artery through its branches: 1. Anterior spinal 2. Posterior spinal 3. Posterior inferior cerebellar 4. Medullary arteries *Basilar artery through its branch: 1. Anterior inferior cerebellar artery
1. There are 4 structures in the ‘midline‘ beginning with M 2. There are 4 structures to the ‘side‘ (lateral) beginning with S 3. There are 4 cranial nerves in the medulla, 4 in the pons and 4 above the pons(2 in the midbrain) 4. The 4 motor nuclei that are in the midline are multiples of
12: ( 3, 4, 6 and 12)
Rule of four
(5, 7, 9 and 11 are in the lateral brainstem)
The 4 structures in the midline: 1. Motor pathway (or corticospinal tract): 2. Medial Lemniscus: 3. Medial longitudinal fasciculus: 4. Motor nucleus and nerve (3,4,6,12)
The 4 ‘side’ (lateral) structures: 1. Spinocerebellar pathway: 2. Spinothalamic pathway: 3. Sensory nucleus of the 5th cranial nerve: 4. Sympathetic pathway:
The 4 cranial nerves in the medulla are CN9-12: 1. Glossopharyngeal (CN9): 2. Vagus (CN10) 3. Spinal accessory (CN11): 4. Hypoglossal (CN12):
The 4 cranial nerves in the pons are CN5-8: 1. Trigeminal (CN5 2. Abducent (CN6) 3. Facial (CN7) 4. Vestibulocochlear (CN8)
The 4 cranial nerves above the pons are CN1-4: 1. Olfactory (CN1): 2. Optic (CN2): 3. Oculomotor (CN3): 4. Trochlear (CN4):
Clinical conditions involving the medulla
1. Lateral medullary syndromes of Wallenberg The lateral part of the medulla is supplied by the posterior inferior
cerebellar artery which is a branch of the vertebral artery.
Affected Structures 1. Nucleus ambiguus 2. Spinal nucleus of trigeminal 3. Vestibular nuclei 4. Inferior cerebellar peduncle 5. Spinal lemniscus/spinothalamic tract
Affected Structures 1. Nucleus ambiguus (dysphagia and dysarthria) 2. Spinal nucleus of trigeminal (analgesia and
thermoanesthesia on the ipsilateral side of the face) 3. Vestibular nuclei (vertigo, nausea, vomiting, nystagmus) 4. Inferior cerebellar peduncle ipsilateral cerebellar signs -
gait and limb ataxia 5. Spinal lemniscus/spinothalamic tract (contralateral loss of
sensation of pain and temperature) 6. Descending sympathetic fibers - ipsilateral Horner Syndrome
2. Medial medullary syndrome The medial part of the medulla is supplied by the vertebral artery. Thrombosis of the medullary branch produces signs due to structures affected by the lesion:
Affected structures:
1. Pyramid : contralateral
hemiparesis
2. Medial lemniscus:
contralateral impaired
sensations of position and
movement and tactile
discrimination
3. Hypoglossal nerve:
ipsilateral paralysis of
tongue muscles
Clinical condition involving the pons
Astrocytoma of the pons occuring in childhood is the most common tumor of the brainstem.
Affected structures: 1. facial nerve nucleus weakness of facial muscles 2. abducent nerve nucleus weakness of the lateral rectus muscle 3. vestibular nucleus nystagmus 4. trigeminal nerve weakness of the jaw muscles 5. cochlear nucleus impairment of hearing 6. corticospinal fibers contralateral hemiparesis 7. medial and spinal lemniscus contralateral sensory defects of the trunk and limbs
