Pyramidal 2012 PDF

8/17/2019 Pyramidal 2012 PDF

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OB J ECTIVES :

1. Enumerate the tracts that constitute thepyramidal system.

2. Trace the pathway of the pyramidal tracts.

3. Locate the position of the lateral and anteriorcorticospinal tracts in a section of thespinal cord.

4. Differentiate an upper motor vs. a lowermotor neuron lesion.

5. Describe briefly the other descending tracts.


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MOTOR SYSTEM

1.PYRAMIDAL SYSTEM= the primary control of voluntary movement thru:a. corticospinalb. corticobulbar pathways

2. EXTRAPYRAMIDAL SYSTEMa. Basal Ganglia (nuclei)b. Cerebellum

supporting role in the production of well-coordinated movements

= influence lower motor neurons indirectlythrough modulation of the cerebral cortex &brainstem


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Cerebral cortexAssociation areas Premotor areas Motor area

(Desire to move) (program) (commands)

BASAL GANGLIAInitiation & Postural Adjustment

Posterior LobeCEREBELLUM

(Coordination) Ant. Lobe FNL BRAINSTEM CENTERS (Supraspinal Reflex Activity)

Vestibular Receptors (Equilibrium)

Intrafusal Stretch Receptors Extrafusal Contractile Fibers

VOLUNTARY MUSCLES

LOWER MOTOR NEURONS (Commands)


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TRACT


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PYRA MIDA L TRA CT

• longest & largestdescending fiber tract(hu m an CNS)

• concerned with voluntary,discrete, skilledmovements; control ofmuscles involved inspeech & vocalization


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• passthrough themedullarypyramids

PYRA MIDA L TRA CT


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PYRA MIDA L TRA CT

• CORTICOSPINAL TRACT Lateral CST

Anterior or Ventral CST

• CORTICOBULBAR TRACT


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PYRA MIDA L TRA CT

Fibers arise from the following areas:

1/3 of axons – precentral gyrus(BA 4) Primary Motor Cortex

* 10% or 3% of CST- Pyramidal Cells of Betz


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ANTERIORHORN CELLS

of BETZ


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PYRA MIDA L TRA CT

Fibers arise from the following areas:

1/3 of axons – precentral gyrus(BA 4) Primary Motor Cortex

1/3 of axons – postcentral gyrus (BA 3,1,2) Primary Sensory Cortex

1/3 of axons – Premotor/ SecondaryMotor Cortex (BA 6 )& some from frontaleye fields (BA 8)


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SENSORIMOTOR CORTEX


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MOTOR HOMUNCUL US

the body has asomatotopicrepresentation

on the PRIMARYMOTOR andPREMOTORCORTEX


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SUPPL EMENTARY MOTOR A REA


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Desc end ing Pathw ays :A natom ical Organizat ion

SERIES OF NEURONS:• 1ST ORDER NEURON

- cel l body in cerebral cor tex

• 2ND ORDER NEURON- in ternunc ial neuron in an te r io r g ray co lumn of SC- shor t axon

• 3RD ORDER NEURON (LMN or

FINAL COMMON PATHWAY)- an ter io r g ray c o lum n o f SC- axon inn ervates skeleta l m us cles throug h anter ior

roo t o f sp ina l nerve


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Desc end ing Pathw ays :A natom ical Organizat ion

SERIES OF NEURONS:• 1ST ORDER NEURON

- ce l l bod y in cerebral cor tex • 2ND ORDER NEURON

- in ternunc ial neuron in an ter io r g ray co lum n of SC- shor t axon

• 3RD ORDER NEURON (LMN or FINAL COMMONPATHWAY)

- an ter io r g ray c o lum n of SC- axon inn ervates skeleta l m us cles throu gh anter ior

root of s pinal nerve

* Some axons of 1 st order neurons terminate directly on 3 rd

order neurons (as in reflex arcs)


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PYRA MIDA L TRA CT

• CORTICOSPINAL TRACT Lateral

Anterior or Ventral CST

• CORTICOBULBAR TRACT


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•

CEREBRAL CORTEX (or ig in)- 1 s t o rde r neuron

• CORONA RADIATA

• INTERNAL CAPSULE

(po s ter ior l imb )

• CEREBRAL PEDUNCLES(mid d le 3/5)

• PONS (break up in to fasc ic les)

• PYRAMIDS (up per m edul la)

• PYRAMIDAL DECUSSATION(caudal m edul la)

CORTICOSPINALTRACT


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• CEREBRAL CORTEX (or ig in)- 1 s t o rde r neuron

• CORONA RADIATA

• INTERNAL CAPSULE (po s ter ior l imb )

• CEREBRAL PEDUNCLES(mid d le 3/5)

• PONS (break up in to fasc ic les)

• PYRAMIDS (up per m edul la)

• PYRAMIDAL DECUSSATION(caudal m edul la)

CORTICOSPINALTRACT


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PYRA MIDA L TRA CT


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• 75 - 90%crossed LATERAL CST

– term inate: ant . grayco lum n of a ll sp ina lcord segments

• 10 - 15%uncrossed ANTERIOR CST

– eventu al ly crossbefore term inat ingon an ter io r horncel ls in cervical &upper thorac icreg ions


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Term inat ion ofPYRA MIDA L TRA CT FIB ERS

Cervical spinal cord level 55%Thoracic level 20%Lumbar / Sacral level 25%


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The cortisospinal tracts are NOT thesole pathway for serving voluntarymovement rather they form thepathway that confers SPEED and

AGILITY to voluntary movements. Theyare believed to control the prime movermuscles while the other descending

tracts are important in controllingsimple basic movements.


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UPPER MOTOR NEURON VS.

L OWER MOTOR NEURON PA RA L YSIS


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UMN


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LMN


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POINTS TO REMEMB ER:

• The pyramidal tract is used commonly byphysicians and refer SPECIFICALLY to theCORTICOSPINAL TRACT.

• The pyramidal tracts normally tend to INCREASE

muscle tone while the extrapyramidal tractsINHIBIT muscle tone.

• In clinical practice, it is rare to have an organiclesion that is restricted only to the pyramidal oronly to the extrapyramidal tracts. Usually BOTHsets of tracts are affected to a variable extentproducing both groups of clinical signs.


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UPPER MOTORNEURON

Paresis

NO muscle atrophy

Spasticity

Hyperreflexia

Clonus

Babinski

loss of certain superficialreflexes:

a. Superficial abdominalb. Cremasteric reflex

LOWER MOTORNEURON

Complete paralysis

WITH muscle atrophy

Flaccidity

Arreflexia

NO clonus

NO Babinski


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UPPER MOTORNEURON

Paresis

NO muscle atrophy

Spasticity

Hyperreflexia

Clonus

Babinski (Extensor Plantar Reflex)

loss of certain superficialreflexes:

a. Superficial abdominalb. Cremasteric reflex

LOWER MOTORNEURON

Complete paralysis

WITH muscle atrophy

Flaccidity

Arreflexia

NO clonus

NO Babinski


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CORTICOB ULB A R TRA CT

Arise from FACE region of primarymotor cortex (BA 4), BA 6 andBA 3,1 & 2

Project : motor nuclei of CNs

III,IV,V,VI,VII,IX,X,XI & XII: parts of reticular formation

(co r t icoret icular f ibers)in pons & medulla

: sensory relay nuclei (gracil is ,cun eatus , senso ry t r igeminalnuc le i, & n ucleus o f sol i taryfasciculus)

Projections are BILATERAL – innervationsfrom BOTH contra & ipsilateral cortex


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CORTICOB ULB A R TRA CT

Project : motor nuclei of CNsIII,IV,V,VI,VII,IX,X,XI & XII

: parts of reticular formation(co r t icoret icular f ibers)in pons & medulla

: sensory relay nuclei (gracil is ,cu neatus , senso ry t r igeminalnuc le i, & n ucleus o f sol i taryfasciculus)

Projections are BILATERAL :

innervations from BOTHcontra & ipsilateral cortex


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The shaded areas of the face show the distribution of facial musclesparalyzed after a supranuclear lesion of the corticobulbar tract &

after a lower motor neuron lesion of the facial nerve

FACIALMOTOR

NUCLEUS


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PERIPHERAL FACIALPARALYSIS (BELL’S PALSY)

* LMN LESION

FACIALMOTOR

NUCLEUS

BELL’S PALSY


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BELL’S PALSY (Perip h eral Facial Paralys is)


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PRA CTICE # 1 :

• CASE SCENARIO: A post-stroke patientwith inability to move the left half of theface but can still wrinkle botheyebrows.

• TYPE OF LESION?• WHERE IS THE LESION?


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PRA CTICE # 2 :

• CASE SCENARIO: A patient uponwaking up in the morning is unable tomove the entire RIGHT half of his face.

• PHHx: had chicken pox 2 weeks prior• TYPE OF LESION?• DIAGNOSIS?• WHERE IS THE LESION?• PROGNOSIS?

FACIAL


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CENTRAL FACIALPARALYSIS

* UMN LESION

PERIPHERAL FACIALPARALYSIS

(BELL’S PALSY) * LMN LESION

FACIALMOTOR

NUCLEUS

HYPOGLOSSAL


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HYPOGLOSSALNUCLEUS

Corticobulbarprojectionsare largelyCONTRALATERAL

LEFT RIGHT


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PRA CTICE # 3 :

• CASE SCENARIO: The resident notedthat the tongue of a post-stroke patientis atrophied and deviated to the LEFT.



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PRA CTICE # 4 :

• CASE SCENARIO: The resident notedthat the tongue of a post-stroke patientis NOT atrophied and deviated to theLEFT.



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OTHER DESCENDING TRA CTSI. MIDBRAINA. Tectospinal and TectobulbarB. Rubrospinal tractC. Interstitiospinal tract

II. PONS/MEDULLAA. Vestibulospinal tracts

1. LATERAL VESTIBULOSPINAL2. MEDIAL VESTIBULOSPINAL

B. Reticulospinal tracts1. PONTINE RETICULOSPINAL TRACT2. MEDULLARY RETICULOSPINAL TRACT


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OTHER DESCENDING TRA CTS

I. MIDBRAINA. Tectospinal and

Tectobulbar

ORIGIN : superior colliculus

FIBERS : cross in dorsal tegmentaldecussation (midbrain)

- incorporated > MLF(m edullary level)

OTHER DESCENDING TRA CTS:


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Tecto sp inal and Tecto bu lbar

TERMINATE: anterior gray column (Rexed lam in ae VI,VII & VIII)in upper cervical segmentsof the spinal cord

FUNCTION: mediate reflex posturalmovements in responseto visual & auditory stimuli(head turning and eye

movements)


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OTHER DESCENDING


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O SC GTRACTS: MIDB RA IN

B. Rubrospinal tractORIGIN : red nucleus (level of

sup erio r co l l i cu lus )

FIBERS : cross immediately inthe ventral tegmentaldecussation > descenddown (bra ins tem) > enterlateral funiculus of SC

TERMINATE: internuncialneurons (anterior graycolumn)

FUNCTION: influence tonecontrol in flexor musclegroups


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OTHER DESCENDING TRA CTS: MIDB RA IN

C. Interstitiospinal tract- or ig in : interstitialnucleus of CAJAL- uncrossed

- forms part of MLF- terminate: anteriorhorn of upper cervicallevels of the SC inlaminae VII and VIII- function: modulatesreflex postural movementsin response to visual &vestibular stimuli

OTHERDESCENDINGTRA CTS


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II. PONS/MEDULLAA. Vestibulospinal tract

1.LATERAL VESTIBULOSPINALORIGIN: lateral vestibular nucleus

> descends in anterolateral funiculusand terminates in Rexed laminae VII& VIII on alpha and gamma motorneurons from cervical & lumbosacrallevels

AFFERENTS: vestibular nerve andcerebellum

FUNCTION: for maintenance of uprightposture and balance (excitesextensor motor neurons innervatingneck, back, forelimb and hindlimbmuscles)

*UNCROSSED



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2. MEDIAL VESTIBULOSOPINAL

ORIGIN : medial vestibular nucleus >

descends in MLF > anterior funiculusof SC (as far as m idtho racic level )

terminates in same laminae as lateral

vestibulospinal tract (Rexed laminaeVII & VIII)

AFFERENTS : primary vestibular& cerebellar

FUNCTION : maintains upright posture(exc i t es neck & backmo tor neurons )

* BOTH CROSSED A ND UNCROSSED


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B. Reticulospinal tracts

1. PONTINE (MEDIAL)RETICULOSPINAL TRACT

- almost entirely IPSILATERAL- descends chiefly in anterior

funiculus of SC (all cord levels,laminae VII & VIII)

- facilitatory to extensormotor neurons

2. MEDULLARY (LATERAL)RETICULOSPINAL TRACT

- fibers project BILATERALLY

to spinal levels- descend both IPSI/CONTRAin lateral funiculus of SC (allcord levels, laminae VII & IX)

- inhibitory to extensormotor neurons


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Medullary ReticulospinalTract :

- provide a pathway bywhich the hypothalamuscan control thesympathetic outflow &sacral parasympatheticoutflow


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Thank you


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REFERENCES :

1. Gilman and Newman. Manter andGatz’s Essentials of ClinicalNeuroanatomy and Neurophysiology,10 th ed., 2003

2. Snell. Clinical Neuroanatomy forMedical Students, 7 th ed., 2010

3. Lansang et al., Modules inNeuroanatomy

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Pyramidal 2012 PDF