The brain stem i bds-ii

Tuesday, April 11, 2023 1

THE BRAIN STEMMEDULLA OBLONGATA

LECTUREBY DR. ANSARI

Chairperson & Prof. Anatomy(FOR BDS SEMESTER-II)


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


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.

http://www.thefullwiki.org/Respiratory_center

http://www.thefullwiki.org/Area_postrema

http://www.thefullwiki.org/Autonomic_nervous_system


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.


The lower part of the medulla, immediately lateral to the fasciculus cuneatus, is marked by another

longitudinal elevation known as the tuberculum cinereum (15)

http://www.thefullwiki.org/Tuberculum_cinereum



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.



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.


Tuberculum gracilis (12) and Tuberculum cuneatus (11)

Posterior surface of medulla/floor of IV ventricle


PICA is a branch from vertebral artery- (11)


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

http://www.thefullwiki.org/Posterior_inferior_cerebellar_artery

http://www.thefullwiki.org/Vertebral_artery

http://www.thefullwiki.org/Medulla_oblongata


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


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


Lateral medullary syndrome can affect structures in upper left: #9,

#10, #12, #13, and #14



Horner’s syndrome - due to compression of sympathetic fibers

1. Miosis2. Anhidrosis3. Loss of pain &

temperature on opposite half of face

4. & Ptosis

http://upload.wikimedia.org/wikipedia/commons/3/37/Miosis.jpg


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.


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

http://en.wikipedia.org/wiki/Ipsilateral

http://en.wikipedia.org/wiki/Hypoglossal_nerve

http://en.wikipedia.org/wiki/Hypoglossal_nerve

http://en.wikipedia.org/wiki/Hemiplegia

http://en.wikipedia.org/wiki/Contralateral

http://en.wikipedia.org/wiki/Medullary_pyramid

http://en.wikipedia.org/wiki/Medullary_pyramid

http://en.wikipedia.org/wiki/Pyramidal_tract

http://en.wikipedia.org/wiki/Pyramidal_tract

http://en.wikipedia.org/wiki/Proprioception

http://en.wikipedia.org/wiki/Contralateral

http://en.wikipedia.org/wiki/Medial_leminiscus

http://en.wikipedia.org/wiki/Medial_leminiscus


Medulla OblongataMotor decussation


Medulla section at pyramidal decussation level/ higher than

previous section

Nuclei gracilis and cuneatus appearing


Open part of medulla


Internal structure of medulla



Medulla at sensory decussation



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


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

http://james.pirruccello.us/index.php?title=CN_VIII&action=edit

http://james.pirruccello.us/index.php?title=CN_IX&action=edit

http://james.pirruccello.us/index.php?title=CN_X&action=edit

http://james.pirruccello.us/index.php?title=CN_XI&action=edit

http://james.pirruccello.us/index.php?title=CN_XII&action=edit


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


Nuclei seen at medulla


The white fibers are

Longitudinally running fibers

1. Corticospinal2. Corticonuclear3. Corticobulbar4. Spinocerebellar5. Spinothalamic6. Medial lemniscus7. Spinal lemniscus

8. Olivocerebellar



Floor of IV ventricle caudal (medulla}:

Vagal trigone ·(7)

Hypoglossal trigone (6)

Area postrema (9) Obex

Medial eminence ·

Sulcus limitans

http://www.thefullwiki.org/Medulla_oblongata

http://www.thefullwiki.org/Vagal_trigone

http://www.thefullwiki.org/Hypoglossal_trigone

http://www.thefullwiki.org/Area_postrema

http://www.thefullwiki.org/Obex

http://www.thefullwiki.org/Medial_eminence_of_floor_of_fourth_ventricle

http://www.thefullwiki.org/Sulcus_limitans


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.


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.


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.


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

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The brain stem i bds-ii