BRAINSTEM-Lec by Emma

8/14/2019 BRAINSTEM-Lec by Emma

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BRAINSTEM

Lecturer: Emmaruth B. Bautista, PTRP


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MEDULLA OBLONGATA

Upper half- cavity of 4

th

ventricleLower half- central canal of SC

ANTERIOR SURFACE OF MEDULLA:AMF- anterior median fissure of SC

PYRAMIDS- one ach side of AMF of SC

Swelling Tapers inferiorly: bundles of nerve fibers,

corticospinal tracts

DECUSSATION OF PYRAMIDS


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1. Anteriormedian fissure

2. Olive

3. Pyramids 4.Cerebellum


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MEDULLA OBLONGATA

OLIVES- posterolateral to pyramidsGroove between PYRAMIDS & OLIVE:

Rootlets ofHYPOGLOSSAL N.

INFERIOR CEREBELLAR PEDUNCLES-Posterior to olives

Connects MO-cerebellum

Groove between OLIVES & INFERIORCEREBELLAR PEDUNCLES:

Rootlets ofGLOSSOPHARYNGEAL, VAGUS &

CRANIAL ROOTS OF ACCESSORY N.


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1.Glossopharyngeal

nerve

2.Vagus nerve 3.Hypoglossal nerve

4.Accessory nerve

5.First cervical spinal

nerve

6.Spinal root of accessory

nerve


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MEDULLA OBLONGATA

POSTERIOR SURFACE OF Medulla Oblongata:Superior half- forms lower part of floor of 4th

ventricle

Inferior half- continuous with SC & possesses

posterior median sulcusGRACILE TUBERCLE- on each side of posterior

median sulcus

Elongated swellingProduced by GRACILE NUCLEUS


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MEDULLA OBLONGATA

CUNEATE TUBERCLE- lateral to gracile nucleusProduced by underlying: CUNEATE

Internal Structure:Considered at 4 levels:

1. pyramids

2. lemnisci

3. olives

4. just inferior to pons


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LEVEL OF DECUSSATION OF

PYRAMIDS

Great motor decussationSuperior part of MO: corticospinal fibers occupy &

form the pyramid

Inferiorly: about of fibers cross median plane &continue down the SC in the lateral white column as

LATERAL CORTICOSPINAL TRACT ( crosses

midline )


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FASCICULUS GRACILLIS &

CUNEATUSContinue to ascend superiorly posterior to central

gray matter

Appears as posterior extensions of central gray

matter

Substantia gelatinosa in posterior gray column

becomes continuous with inferior end ofNUCLEUS

OF SPINAL TRACT OF TRIGEMINAL N.


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LEMNISCI

Great sensory decussationTakes place anterior to central gray matter &

posterior to pyramids

Have bee formed from: INTERNAL ARCUATE

FIBERS

Which has emerged from the anterior aspect of

the NUCLEUS GRACILIS & NUCLEUS

CUNEATUS


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LEMNISCI

NUCLEUS OF SPINAL TRACT OF TRIGEMINALN.-

lies lateral to internal arcuate fibers

SPINAL TRACT OF TRIGEMINAL N.- Lies lateral to nucleus

LATERAL & ANTERIOR SPINOTHALAMIC

TRACTS & TECTAL TRACTS

Lateral to decussation of lemnisci

Collectively known as: SPINAL LEMNISCUS


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LEMNISCI

SPINOCEREBELLAR, VESTIBULOSPINAL &RUBROSPINAL TRACTS-

Situated anterolateral region of Medulla Oblongata


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LEVEL OF OLIVESTransverse section passes across inferior part of 4th

ventricle

Amount of gray matter has increased at this level

OLIVARY NUCLEAR COMPLEX:

INFERIOR OLIVARY NUCLEUS Largest nucleus of this complex

Gray matter shaped-bag, mouth directed mediallyResponsible for elevation on surface of medulla called

OLIVES


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OLIVARY NUCLEAR COMPLEX

Smaller dorsal & medial accessory olivary nuclei

are also present

Send fibers medially across midline to enter

cerebellumSPINO-OLIVARY TRACTS

Function is associated with voluntary movement


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VESTIBULOCOCHLEAR NUCLEIVESTIBULAR COMPLEX:

1. medial vestibular nucleus

2. inferior vestibular nucleus

3. lateral vestibular nucleus

4. superior vestibular nucleus

2 COCHLEAR NUCLEI:

1. anterior cochlear ( anterolat of ICP )

2. posterior cochlear ( post of ICP )


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NUCLEUS AMBIGUUS

Large motor neurons

Situated deep w/in reticular formation

Joins CN IX, X, XI ( cranial part ) distributed to

voluntary muscles

CENTRAL GRAY MATTER

Lies beneath floor of 4th ventricle ( M-L )

1. hypoglossal nucleus 2. dorsal nucleus of vagus

3. nucleus of tractus solitarius

4. medial & inferior vestibular nuclei


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ARCUATE NUCLEI

Inferior displaced pontine nuclei

Efferent fibers to cerebellum- EXTERNALARCUATE FIBERS

PYRAMIDS CORTICOSPINAL & CORTICONUCLEAR FIBERS

MEDIAL LEMNISCUS Flattened tracts on each side of midline posterior to pyramid

Emerge from decussation of lemnisci

Convey sensory information to thalamus


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MEDIAL LONGITUDINAL FASCICULUS

Forms small tract of fibers situated on each side of

midline posterior to medial lemniscus & anterior tohypoglossal nucleus

INFERIOR CEREBELLAR PEDUNCLES In posterolateral corner on lateral side of 4th ventricle

SPINAL TRACT OF CN V & ITS NUCLEUS On antermedial aspect of ICP

ANTERTIOR SPINOCEREBELLAR TRACT

Between inferior olivary & nucleusof spinal tract of CN VRETICULAR FORMATION

Deep posterior to olivary nucleus


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1.Nuclei of oculomotor

nerve

2.Trochlear nucleus

3.Pons 4.Fourth ventricle

5.Abducent nucleus

6.Vestibular nucleus

7.Medial longitudinal

fasciculus


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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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IX, X & Cranial part of Accessory N.

can be seen running forward & lateral through

reticular formation

HYPOGLOSSAL N.

Run anterior & lateral through reticular

LEVEL JUST INFERIOR TO PONSNo major changes

Lateral vestibular nucleus has replaced

inferior vestibular nucleus

Cochlear nucleus now are visible on anterior

& posterior surface of ICP


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PONSGROSS APPEARANCE:

Convex anterior surface

Transverse fibers converge to form MCP

BASILAR GROOVE

lodges basilar artery

On anterolat side: emerges CN V on each side

Motor root: smaller, medial part

Sensory root: larger, lateral part

Groove between PONS & MO ( M-L )

CN VI, VII, VIII

1 Cerebral peduncle


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1.Cerebral peduncle

2.Basilar groove

3.Olive

4.Pyramid 5.Trigeminal nerve

6.Abducent nerve


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POSTERIOR SURFACE:

Limited laterally by SCP

MEDIAN SULCUS- divides pons symmetrically MEDIAL EMINENCE-

Bounded by sulcus limitans

Lateral to sulcus

FACIAL COLLICULUS Slight expansion on inferior end of medial eminence

SUBSTANTIA FERRUGINEA

Bluish gray in superior part of sulcus limitans

AREA VESTIBULI

Lateral to sulcus limitans

Underlying vestibular nuclei


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1.Substantia ferruginea

2.Facial colliculus

3.Striae medullares

4.Vestibular area 5.Hypoglossal triangle

6.Vagal triangle

7.Calamus scriptorius


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INTERNAL STRUCTURE OF PONS:Divided into:

TEGMENTUM- posterior part BASAL PART- anterior part TRAPEZOID BODY- divides tegmentum & basal part

TRANSVERSE SECTION THROUGH CAUDAL

PART:Medial LemniscusFacial NucleusNucleus of abducent nerve

Facial colliculusMedial longitudinal fasciculusMedial vestibular nucleusPosterior & anterior cochlear nuclei

Spinal nucleus of CN V


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TRAPEZOID BODY Fibers derived from cochlear nuclei & nuclei of trapezoid

body

BASILAR PART OF PONS:

Contains small masses of nerve cells: PONTINE

NUCLEICORTICOPONTINE FIBERS of crus cerebri

terminate in pontine nuclei

TRANSVERSE FIBERS enter middle cerebellar

peduncle


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TRANSVERSE SECTION THROUGH

CRANIAL PART

Motor nucleus of trigeminal nerve

Principal sensory nucleus of trigeminal nerve

Superior cerebellar peduncleAnterior cerebellar tract

Trapezoid body


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MIDBRAIN

CEREBRAL AQUEDUCTNarrow channel traversing midbrain

Filled with CSF

POSTERIOR SURFACE OF MIDBRAIN:COLLICULI ( Corpora Quadrigemina )

Rounded eminences divided into superior &

inferior pairs by a vertical & transverse groove.

SUPERIOR COLLICULI- centers for visual

reflexes

INFERIOR COLLICULI- lower auditory centers


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TROCHLEAR- emerges in the midline below

inferior colliculi

LATERAL ASPECT OF MIDBRAIN:SUPERIOR BRACHIUM

Passes from superior colliculus to lateralgeniculate body & optic tract

INFERIOR BRACHIUM

Connects inferior colliculus to:MEDIAL GENICULATE BODY


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ANTERIOR ASPECT OF MIDBRAIN:

INTERPENDICULAR FOSSA

Deep depression in the midline, bound on eachside by:

CRUS CEREBRI

POSTERIOR PERFORATED SUBSTANCEMany small blood vessels that perforate the floor

of the interpendicular fossa

OCCULOMOTOR NERVEemerges from agroove on medial side of crus cerebri & passes

forward in lateral wall of cavernous sinus


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INTERNAL STRUCTURE OF MIDBRAIN:Midbrain comprises 2 lateral halves:

CEREBRAL PEDUNCLES, each divided into:CRUS CEREBRI- anterior part &TEGMENTUM- posterior part by:SUBSTANTIA NIGRA- pigmented band of gray

matterCEREBRAL AQUEDUCT- narrow cavity w/c

connects 3rd & 4th ventricle

TECTUM- part of midbrain posterior to cerebralaqueduct & has 4 swellings: 2 SUPERIOR COLLICULI 2 INFERIOR COLLICULI


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TRANSVERSE SECTION OF MB AT

LEVEL OF INFERIOR COLLICULI

INFERIOR COLLICULUSTROCHLEAR NUCLEUS

Situated in gray matter close to median plane just

posterior to the: MEDIAL LONGITUDINALFASCICULUS

MESENCEPHALIC NUCLEI OF CN V are lateralto cerebral aqueduct

DECUSSATION OF SUPERIOR CEREBELLARPEDUNCLES

Occupies central part of tegmentum anterior to

cerebral aqueduct

RETICULAR FORMATION


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RETICULAR FORMATIONMEDIAL LEMNISCUS

Ascends posterior to substantia nigra

SPINAL & TRIGEMINAL LEMNISCI Situated lateral to medial lemniscus

LATERAL LEMNISCUS Posterior to trigeminal lemniscus

SUBSTANTIA NIGRA Large motor nucleus situated between tegmentum & crus

cerebri Concerned w/ mm tone, connected to Cerebral cortex, SC,

hypothalamus & basal nucleiCRUS CEREBRI

Coticospinal & corticonuclear occupy middle 2/3of crus Frontopontine fibers on lateral part


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TRANSVERSE SECTION OF MB AT

LEVEL OF SUPERIOR COLLICULI

SUPERIOR COLLICULUS

LIGHT REFLEX- PRETECTAL NUCLEUS

OCCULOMOTOR NUCLEUS situated in centralgray matter close to median plane, just posteriortoMEDIAL LONGITUDINAL FASCICULUS

MEDIAL, SPINAL & TRIGEMINAL LEMNISCI

Form a curved band posterior to substantia nigra butLATERAL LEMNISCUS does not extend superiorly to

this level

1 Pi l l d


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1.Pineal gland

2.superior colliculus

3.Inferior colliculus

4.Trochlear nerve 5.Fourth ventricle

6.Pulvinar of thalamus

7.Superior cerebellar

peduncle


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RED NUCLEUS

Rounded mass of gray matter situated between

cerebral aqueduct & substantia nigraRedish hue is due to its vascularity & presence

of iron containing pigment in cytoplasm ot its

neurons.

RETICULAR FORMATION

Situated in tegmentum lateral & posterior to red

nucleus

CRUS CEREBRI Contains identical, important descending tracts:

CORTICOSPINAL, CORTICONUCLEAR,

CORTICOPONTINE fibers


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BRAINSTEM STROKE

SYNDROMESTWO GENERAL MANIFESTATIONS

EXPECTED OF A BRAINSTEM STROKE: 1. Contralateral hemiplegia

2. Ipsilateral Cranial Nerve Palsy

Also known as ALTERNATING/ CROSSED

HEMIPLEGIA


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WEBERS SYNDROME

MEDIAL BASAL MIDBRAIN

Contralateral Hemiplegia

Ipsilateral CN 3 Palsy( Ipsilateral Ptosis )


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BENEDIKTS SYNDROME

TEGMENTUM OF MIDBRAINCONTRALATERAL:

Pain & temperature loss

Joint position loss Ataxia

Chorea

IPSILATERAL:CN 3 palsy


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LOCKED IN SYNDROME

BILATERAL PONS

Bilateral Hemiplegia

Bilateral CN Palsy


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WALLENBERGS or LATERAL

MEDULLARY SYNDROME

LATERAL MEDULLA

IPSILATERAL:Loss of FACIAL SENSATION

Hemiataxia

Horners syndrome

Nystagmus

dysphagia

CONTRALATERALLoss of pain & temperature


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LEFT VS. RIGHT CVALEFT BRAIN FUNCTIONS

Language/Communications

Higher skill

logic

RIGHT BRAIN FUNCTIONS Perception

Imagination

Memory

The arts & music


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LEFT VS. RIGHT CVA

LEFT CVA a.k.a : Left hemispheric lesion

Dominant hemispheric lesion or CVA

Right hemiplegic

RIGHT CVA a.k.a :Right hemispheric lesion

Non-dominant Hemispheric lesion or CVA

Left hemiplegic


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