Download - The brain stem i bds-ii
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THE BRAIN STEMMEDULLA OBLONGATA
LECTUREBY DR. ANSARI
Chairperson & Prof. Anatomy(FOR BDS SEMESTER-II)
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OBJECTIVES
Gross features of medulla oblongata. Blood supply of medulla. Cranial nerves attachments to medulla Nuclei situated in medulla White fibers/tracts passing through
medulla
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Functions of medulla
The medulla contains the cardiac, respiratory,
vomiting and vasomotor centers and deals
with
autonomic functions, such as breathing, heart
rate and blood pressure.
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Medulla oblongata is an oval mass
Cylindrical mass of brain tissue that connects the brain with spinal cord.
It has anterior and posterior surfaces, anterior surface having anterior median line interrupted by decussation of white fibers, the motor decussation.
On ventral surface , pyramids are two elevations followed by anteriolateral oval swellings, the olives.
The hypoglossal nerve rootlets are arising from the sulcus between olive and pyramids.
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The lower part of the medulla, immediately lateral to the fasciculus cuneatus, is marked by another
longitudinal elevation known as the tuberculum cinereum (15)
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The posterior surface of medulla
Posterior to the olive, the sulcus is having the emergence of glossopharyngeal nerve,vagus and accessory nerve rootlets.
On the posterior surface there are two tracts running parallel to the posteromedian sulcus,
The fasciculus gracilis and fasciculus cuneatus. These two fasciculi superiorly ends up in the
corresponding tuberculum, tubercle of gracile and tubercle of cuneatus.
Rostrally there is an open part of medulla that form the floor of VI ventricle.
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The medulla oblongata and spinal cord is connected
To cerebellum by means of inferior cerebellar peduncles.
The medulla passes out of foramen magnum and becomes continuous with the spinal cord.
The two vertebral arteries enter the foramen magnum and fuse with each other at the lower border of pons to form the basilar artery.
The vertebral artery give rise to PICA branch(posterior inferior cerebellar artery) which also supplies lateral aspect of medulla.
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Tuberculum gracilis (12) and Tuberculum cuneatus (11)
Posterior surface of medulla/floor of IV ventricle
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PICA is a branch from vertebral artery- (11)
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The lateral medullary 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.
Wallenberg syndrome
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The white fibers at this level are
1. fasciculus gracilis2. fasciculus cuneatus3. spinal nucleus & tract of trigeminal4. spinocerebellar tract5. Motor decussation6. lateral spinothalamic tract7. Pyramids
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DYSFUNCTION EFFECT
Vestibular nuclei Vertigo, nystagmus,vomiting &diplopia
Inferior cerebellar peduncles Ipsilateral cerebellar signs, ataxia
Nucleus ambiguous(IX,X,XI) Dysphagia,hoarseness, diminished gag reflex
Spinal trigeminal nucleus Ipsilateral loss of touch,pain &temperature sensation from face
Lateral spinothalamic tract Contralateral deficits in pain and temperature from body
Sympathetic fibers Ipsilateral Horner's syndrome
Features of lateral medullary syndrome/ Wallenberg syndrome
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Lateral medullary syndrome can affect structures in upper left: #9,
#10, #12, #13, and #14
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Horner’s syndrome - due to compression of sympathetic fibers
1. Miosis2. Anhidrosis3. Loss of pain &
temperature on opposite half of face
4. & Ptosis
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Medial medullary syndrome
The infarction leads to death of the ipsilateral medullary pyramid, the ipsilateral medial lemniscus, and hypoglossal nerve fibers that pass through the medulla.
It is also called as "Dejerine syndrome.
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Dejerine syndrome/Medial medullary syndrome
Description Source of damage
A deviation of the tongue to the Ipsilateral side of the infarct on attempted protrusion, caused by muscle weakness on the Ipsilateral side
Hypoglossal nerve fibers
Limb weakness (or hemiplegia, depending on severity), on the contralateral side of the infarct
Medullary pyramid and hence to the Corticospinal fibers of the pyramidal tract
A loss of discriminative touch, conscious proprioception, and vibration sense on the contralateral side of the infarct
Medial leminiscus
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Medulla OblongataMotor decussation
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Medulla section at pyramidal decussation level/ higher than
previous section
Nuclei gracilis and cuneatus appearing
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Open part of medulla
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Internal structure of medulla
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Medulla at sensory decussation
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The various nuclei at the level of medulla are
1. Gracile nucleus2. Cuneate nucleus3. Nucleus of the spinal tract of trigeminal4. Hypoglossal nucleus5. Dorsal vagal nucleus6. Nucleus Ambiguues7. Nucleus of the Tractus Solitarius8. Inferior olivary nuclei complex9. Arcuate nucleus
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In the medulla the following cranial nerve nuclei are found
CN VIII, Vestibulocochlear
CN IX, Glossopharyngeal
CN X, Vagus
CN XI, Accessory
CN XII, Hypoglossal
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1. Inferior cerebellar peduncle
2. Floor of fourth ventricle
3. Hypoglossal nucleus 4. Medial longitudinal
fasciculus 5. Reticular formation 6. Medial lemniscus 7. Arcuate nuclei 8. Inferior olivary
nucleus 9. Pyramids
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Nuclei seen at medulla
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The white fibers are
Longitudinally running fibers
1. Corticospinal2. Corticonuclear3. Corticobulbar4. Spinocerebellar5. Spinothalamic6. Medial lemniscus7. Spinal lemniscus
8. Olivocerebellar
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Floor of IV ventricle caudal (medulla}:
Vagal trigone ·(7)
Hypoglossal trigone (6)
Area postrema (9) Obex
Medial eminence ·
Sulcus limitans
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The medial lemniscus
It is formed by internal arcuate fibers that arise from the nuclei gracilis and cuneatus and ascend upwards in the brain stem to terminate in the thalamus.
They carry fine touch, vibration and conscious proprioception.
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The spinal lemniscus
This tract is involved in the perception of touch, temperature, and sharp pain.
It is composed of three separate tracts,
The spinothalamic tract,
The spinoreticular tract, and
The spinotectal tract.
The pyramidal tract A motor tract descending
from cerebral cortex and pass through the brain stem, at medulla level 90% of the fibers migrate to the opposite side as motor decussation and runs in contralateral side as lateral corticospinal tract.
This carry upper motor neuron fibes from motor cortex.
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Applied anatomy
Bulbar paralysis is Glosso-Labio-Laryngeal Paralysis due to atrophy of the grey nuclei at medulla.
XII nerve paralysis A lower motor neurone (LMN) lesion produces
wasting of the ipsilateral side of the tongue, with fasciculation; and on attempted protrusion the tongue deviates towards the affected side, but the tongue deviates away from the side of a central lesion.
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A 68-year-old woman has the sudden onset of weakness in her right arm and leg
She can speak, but her words are not enunciated clearly. Neurologic examination 6 weeks later shows an extensor plantar reflex on the right. When she is asked to protrude her tongue, it deviates to the left, and the muscle in the left side of the tongue shows considerable atrophy. Which of the following labeled areas in the transverse sections of the brain stem is most likely damaged?A.B.C.D.E