1 extra pyramidal system 2 motor neuron lesions
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1- EXTRA PYRAMIDAL SYSTEM 2- MOTOR NEURON LESIONS. Lecture 7 DR ZAHOOR ALI SHAIKH. EXTRA PYRAMIDAL SYSTEM. DEFINATION Tracts other than corticospinal tracts are known as EXTRA PYRAMIDAL TRACTS. COMPONENTS OF EXTRAPYRAMIDAL SYSTEM. BASAL GANGLIA BRAINSTEM Giving rise to following tracts:

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1- EXTRA PYRAMIDAL SYSTEM 2- MOTOR NEURON LESIONS

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1 extra pyramidal system 2 motor neuron lesions

1- EXTRA PYRAMIDAL SYSTEM2- MOTOR NEURON LESIONS

Lecture 7

DR ZAHOOR ALI SHAIKH


Extra pyramidal system

EXTRA PYRAMIDAL SYSTEM

DEFINATION

  • Tracts other than corticospinal tracts are known as EXTRA PYRAMIDAL TRACTS.


Components of extrapyramidal system

COMPONENTS OF EXTRAPYRAMIDAL SYSTEM

  • BASAL GANGLIA

  • BRAINSTEM Giving rise to following tracts:

    • Rubrospinal tract

    • Vestibulospinal tract

    • Reticulospinal tract

    • Tectospinal tract


Rubrospinal tract

RUBROSPINAL TRACT

  • Origin – Red nucleus mid brain

  • Input - Red nucleus gets input from both cerebellum and cerebral cortical motor areas

  • Output - Via Rubrospinal tract is directed to contralateral spinal motor neurons ( crosses to opposite side at the level of nucleus and axons are located in lateral spinal white matter anterior to corticospinal tract.

  • Functions - Involved in movements of distal limbs (hand & feet) also regulates tone and posture.

  • It is excitatory to flexors and inhibitory to extensor muscles.


Vestibulospinal tract

VESTIBULOSPINAL TRACT

  • Location - Vestibular nuclei are located in Pons and Medulla

  • Input - They receive input from Vestibular apparatus in the inner ear and Cerebellum

  • Output – Mainly From Lateral vestibular nuclei to spinal cord in Vestibulospinal tract. It remains ipsilatterall

  • Function - Excitatory to ipsilateral extensor. Inhibitory to flexors muscles

  • Regulates muscle tone for maintaining balance in response to head movement


Reticulospinal tract

RETICULOSPINAL TRACT

  • Location - Reticular formation in the central grey matter of brain stem

  • Input - Afferent input to reticular formation comes from spinal cord, vestibular nuclei, cerebellum, Sensory motor cortex, globus pallidus & Lat. Hypothalamus

  • Output - Descending tract arise from nuclei in pons and medulla

    1] Pons – Pontine Reticulospinal tract runs ipsilaterally;

    Function - Excitatory to Axial extensor muscles

    2] Medulla – Medullary reticulospinal tract runs ipsilaterally (some cross also)

    Function - Inhibitory to axial extensor Muscle


Tectospinal tract

TECTOSPINAL TRACT

  • Loacation – originates in superior colliculus in midbrain

  • Input – from visual stimuli

  • Output - Conveys nerve impulses from superior colliculus (midbrain) to contralateral skeletal muscles that move the head and eyes in response to visual stimuli

  • Function – Involved in control of neck muscle in response to visual stimuli


Descending extra pyramidal motor tract to spinal interneuron and motor neuron

DESCENDING EXTRA PYRAMIDAL MOTOR TRACT TO SPINAL INTERNEURON AND MOTOR NEURON

&

uncrossed

These tracts terminate on anterior horn interneurons. Occasionally they terminate directly on anterior horn motor neurons


Summary of pyramidal and extrapyramidal pathways

SUMMARY OF PYRAMIDAL AND EXTRAPYRAMIDAL PATHWAYS


Transverse section spinal cord

TRANSVERSE SECTION SPINAL CORD


Extra pyramidal system or multineuronal system

EXTRA PYRAMIDAL SYSTEM OR MULTINEURONAL SYSTEM

  • It has multiple synapses that involve many regions of brain

  • Final link in extra pyramidal pathway is brain stem, which is influenced by motor cortex, cerebellum, basal nuclei [therefore these brain regions regulate motor activity indirectly]

    Note – Direct influence on anterior home cell is by primary motor cortex


Functions of extra pyramidal system or multineuronal system

FUNCTIONS OF EXTRA PYRAMIDAL SYSTEMORMULTINEURONAL SYSTEM

  • REGULATION OF BODY POSTURE, INVOLVING INVOLUNTARY MOVEMENTS OF LARGE MUSCLE GROUPS OF TRUNK AND LIMBS

  • REGULATION OF VOLUNTARY MOVEMENT

  • REGULATION OF TONE


Important

IMPORTANT

  • Complex and overlapping function exist between Pyramidal and extra pyramidal systems for example while doing fine work like needle work (Pyramidal system) one has to subconsciously assume a particular posture of arms( extra pyramidal system) that enables to do your work


Applied

APPLIED

  • Extra pyramidal tracts

    some are excitatory and other are inhibitory to muscle tone

    overall effect – strong inhibitory effect over Gamma Motor Neuron in anterior horn cell

    What will be the effect of extra pyramidal lesions ?

  • Hypertonia

    Why ?

    - Because strong inhibitory effect over Gamma motor neuron is lost.


Difference between pyramidal and extra pyramidal tracts

Difference between pyramidal and extra pyramidal tracts

  • EXTRA PYRAMIDAL TRACTS

  • -Rubrospinal

  • -Vestibulospinal

  • -Reticulospinal

  • -Tectospinal

  • They originate in Midbrain and brainstem nuclei and have influence of cerbral cortex, basal ganglia and cerebellum which can stimulate or inhibit these nuclei

  • No direct control of motor cortex or basal ganglia on spinal cord but via nuclei in midbrain and brainstem

PYRAMIDAL TRACTS

  • -Lateral corticospinal

    -Ant. or ventral corticospinal

    - Corticobulbar

  • Cell bodies that contribute to pyramidal tracts are located in precentral gyrus ( Primary, Premotor and supplimentary motor cortex) and somatosensory area.

  • Pyramidal tract descend directly without synaptic interruption from cerebral motor cortex to spinal cord ( on interneuron and ant. Horn cells)


Difference between pyramidal and extra pyramidal tracts contd

Difference between pyramidal and extra pyramidal tracts Contd . . .

  • EXTRA PYRAMIDAL TRACTS

  • Major extra pyramidal tracts, some cross and others are uncrossed (see table given before)

  • Function:

  • Control of body posture involving involuntary movements of axial and Proximal limb muscle

PYRAMIDAL TRACTS

  • 80 % of Corticospinal tracts (lateral) cross in medulla

    20 % of corticospinal tract (ventral) cross in spinal cord

    Because of crossing cerebral cortex controls opposite side of the body

  • Function:

    - Lat. Corticospinal tract – fine movement of fingers eg. Writing, needle work

    - Ventral corticospinal tract – Axial or Postural Movement


Common words used in neurophysiology and clinical neurology

COMMON WORDS USED IN NEUROPHYSIOLOGY AND CLINICAL NEUROLOGY

  • PYRAMIDAL TRACTS

  • EXTRAPYRAMIDAL TRACTS

  • PYRAMIDAL LESION – HYPOTONIA

    Pure pyramidal lesions usually don’t occur in humans

  • EXTRAPYRAMIDAL LESIONS – HYPERTONIA (Rigidity)

  • UMN (Upper motor neuron) – Motor tracts coming from Brain to Ant. Horn cells [Pyramidal and extra pyramidal tracts]


1 extra pyramidal system 2 motor neuron lesions

Motor System

It is two neuron system

1- Upper motor neuron – From motor cortex to anterior horn cell of spinal cord

2- Lower motor neuron – Starts from anterior horn cell and ends on muscle e.g. all peripheral nerves


2 motor neuron lesions

2- MOTOR NEURON LESIONS


1 extra pyramidal system 2 motor neuron lesions

  • UMN lesion causes

    • Increased tone (Spasticity)

    • Increased reflexes

    • Clonus: Repetitive contraction and relaxation of muscle in oscillating fashion every second or so

    • Babinski sign: stimulation of the sole of the foot along outer border causes extension of big toe upward and fanning of other toes

      (Normally in adults this stimulation causes plantar reflex that is downward flexion of big and small toes.)

      Note: below one year of age Babinski reflex is normally present. Why ?


1 extra pyramidal system 2 motor neuron lesions

Babinski’s sign is hard sign for upper motor neuron lesion, signifies damage to lateral corticospinal tract


1 extra pyramidal system 2 motor neuron lesions

LMN

  • LMN (Lowe motor neuron) – Motor neuron from anterior horn cells to the skeletal muscle( peripheral nerves).

  • Lower motor neuron also from nuclei of cranial nerves to the skeletal muscles of face and head.


Lmn lesion

LMN Lesion

  • LMN lesion (As final pathway to the muscle is damaged)

    • Decreased tone (Hypotonia / Flaccidity).

    • Decreased power of the muscles.

    • Decreased reflexes.

    • Wasting of muscles.


Difference between upper lower motor neuron lesion

UMN LESION

Paralysis affect movement rather than muscles

Muscle wasting is only from disuse, therefore slight. Occasionally marked in chronic severe lesions.

Spasticity of clasp-knife’ type. Muscles hypertonic.

LMN LESION

Individual muscle or group of muscles are affected.

Wasting pronounced.

Flaccidity. Muscles hypotonic.

DIFFERENCE BETWEEN UPPER & LOWER MOTOR NEURON LESION


1 extra pyramidal system 2 motor neuron lesions

UMN LESION

Tendon reflexes increased. Clonus often present.

Superficial reflexes diminished or modified.

Abdominal reflex absent.

Babinski’s sign +ve,

--Increased jaw jerk.

LMN LESION

Tendon reflexes diminished or absent.

Superficial reflexes often unaltered.


Common words used in neurophysiology and clinical neurology1

COMMON WORDS USED IN NEUROPHYSIOLOGY AND CLINICAL NEUROLOGY

  • HEMIPLEGIA – Paralysis (loss of power) of half side of the body

  • HEMIPARESIS – Partial loss of power of half side of the body

  • PARAPLEGIA – Paralysis in both legs

  • PARAPARESIS – Partial loss of power in both legs

  • QUADRIPEGIA – Paralysis in all four limbs

  • MONOPLEGIA – Paralysis in one limb


1 extra pyramidal system 2 motor neuron lesions

We will see some lesions of sensory and motor system


1 extra pyramidal system 2 motor neuron lesions

R

L

Lesion of the right dorsal column at L1 produces what impairment?

Click for answer

Damage to the right dorsal column at L1 causes the absence of light touch, vibration, and position sensation in the right leg. Only fasciculus gracilis exists below T6.

Click for explanation


1 extra pyramidal system 2 motor neuron lesions

Ipsilateral loss of light touch, vibration, and position sense

generalized below the lesion level

Below T6 only the fasciculus gracilis is present.

Right Dorsal Column Lesion

Click to animate

DRG

R

L

L1

Dorsal column lesion

Common causes include MS, penetrating injuries, and compression from tumors.


1 extra pyramidal system 2 motor neuron lesions

R

L

Lesion of the right lateral spinothalamic tract at L1 produces what impairment?

Click for answer

Damage to the right lateral spinothalamic tract at L1 causes the absence of pain and temperature sensation in the left leg.

Click for explanation


1 extra pyramidal system 2 motor neuron lesions

Contralateral loss of pain and temperature sense

Right Lateral Spinothalamic Tract Lesion

Click to animate

DRG

R

L

L1

Lateral spinothalamic tract lesion

Common causes include MS, penetrating injuries, and compression from tumors.


1 extra pyramidal system 2 motor neuron lesions

R

L

Lesion of the right lateral corticospinal tract at L1 produces what impairment?

Click for answer

Damage to the right lateral corticospinal tract at L1 causes upper motor neurons signs (weakness or paralysis, hyperreflexia, and hypertonia) in the right leg.

Click for explanation


1 extra pyramidal system 2 motor neuron lesions

Ipsilateral upper motor neurons signs

generalized below the lesion level

UMN signs

Weakness (Spastic paralysis)

Hyperreflexia (+ Babinski, clonus)

Hypertonia

Right Lateral Corticospinal Tract Lesion

UMN

Click to animate

R

L

L1

Lateral corticospinal tract lesion

Common causes include penetrating injuries, lateral compression from tumors, and MS.


1 extra pyramidal system 2 motor neuron lesions

Complete transection of the right half the spinal cord (Hemicord or Brown-Sequard syndrome) at L1 produces what impairments?

R

L

Click for answer

Damage to the right dorsal columns at L1 causes the absence of light touch, vibration, and position sense in the right leg. Damage to the lateral corticospinal tract causes upper motor neuron signs in the right leg (Monoplegia), and damage to the lateral spinothalamic tract causes the absence of pain and temperature sensation in the left leg.

Click for explanation


1 extra pyramidal system 2 motor neuron lesions

R

L

Dorsal column lesion

Ipsilateral loss of light touch, vibration, and position sense

Lateral corticospinal tract lesion

Ipsilateral upper motor neurons signs

Lateral spinothalamic tract lesion

Contralateral loss of pain and temperature sense

Hemicord lesion

Hemicord Lesion (Brown-Sequard Syndrome)

Click to animate

L1

Common causes include penetrating injuries, lateral compression from tumors, and MS.

Build the lesion


1 extra pyramidal system 2 motor neuron lesions

Ipsilateral loss of light touch, vibration, and position sense

Ipsilateral upper motor neurons signs

Contralateral loss of pain and temperature sense

Hemicord lesion

Hemicord Lesion (Brown-Sequard Syndrome)

UMN

Click to animate

DRG

R

L

DRG

L1

Dorsal column lesion

Lateral corticospinal tract lesion

Lateral spinothalamic tract lesion


Thank you

Thank you


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