Transcript extra pyramidal system - Mcst

1- EXTRA PYRAMIDAL
SYSTEM
2- MOTOR NEURON
LESIONS
Lecture 7
DR ZAHOOR ALI SHAIKH
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EXTRA PYRAMIDAL SYSTEM
DEFINATION
• Tracts other than corticospinal tracts are known
as EXTRA PYRAMIDAL TRACTS.
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COMPONENTS OF
EXTRAPYRAMIDAL SYSTEM
• BASAL GANGLIA
• BRAINSTEM Giving rise to following tracts:
o Rubrospinal tract
o Vestibulospinal tract
o Reticulospinal tract
o Tectospinal tract
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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.
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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
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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
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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
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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
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SUMMARY OF PYRAMIDAL AND
EXTRAPYRAMIDAL PATHWAYS
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TRANSVERSE SECTION SPINAL CORD
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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
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FUNCTIONS OF EXTRA PYRAMIDAL SYSTEM
OR
MULTINEURONAL SYSTEM
• REGULATION OF BODY POSTURE,
INVOLVING INVOLUNTARY MOVEMENTS
OF LARGE MUSCLE GROUPS OF TRUNK AND
LIMBS
• REGULATION OF VOLUNTARY MOVEMENT
• REGULATION OF TONE
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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
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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.
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Difference between pyramidal and extra pyramidal tracts
1.
2.
3.
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)
EXTRA PYRAMIDAL TRACTS
1. -Rubrospinal
-Vestibulospinal
-Reticulospinal
-Tectospinal
2. They originate in Midbrain and
brainstem nuclei and have
influence of cerbral cortex,
basal ganglia and cerebellum
which can stimulate or inhibit
these nuclei
3. No direct control of motor
cortex or basal ganglia on spinal
cord but via nuclei in midbrain
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and brainstem
Difference between pyramidal and extra pyramidal tracts
Contd . . .
4.
5.
PYRAMIDAL TRACTS
EXTRA PYRAMIDAL TRACTS
80 % of Corticospinal tracts
4. Major extra pyramidal tracts,
(lateral) cross in medulla
some cross and others are
uncrossed (see table given
20 % of corticospinal tract
before)
(ventral) cross in spinal cord
Because of crossing cerebral
cortex controls opposite side
of the body
Function:
5. Function:
- Lat. Corticospinal tract – fine
Control of body posture
movement of fingers eg.
involving involuntary
Writing, needle work
movements of axial and
- Ventral corticospinal tract –
Proximal limb muscle
Axial or Postural Movement
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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]
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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
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2- MOTOR NEURON LESIONS
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• UMN lesion causes
o Increased tone (Spasticity)
o Increased reflexes
o Clonus: Repetitive contraction and relaxation of
muscle in oscillating fashion every second or so
o 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 ?
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Babinski’s sign is hard sign for upper motor neuron lesion, signifies
damage to lateral corticospinal tract
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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.
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LMN Lesion
• LMN lesion (As final pathway to the muscle is damaged)
o Decreased tone (Hypotonia / Flaccidity).
o Decreased power of the muscles.
o Decreased reflexes.
o Wasting of muscles.
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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.
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UMN LESION
• Tendon reflexes
increased. Clonus often
present.
• Superficial reflexes
diminished or modified.
Abdominal reflex absent.
Babinski’s sign +ve,
LMN LESION
• Tendon reflexes
diminished or absent.
• Superficial reflexes often
unaltered.
--Increased jaw jerk.
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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
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• We will see some lesions of sensory
and motor system
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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
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Right Dorsal Column Lesion
Click to animate
DRG
R
L
L1
Dorsal column lesion
Common
causes
include MS,
penetrating
injuries, and
compression
from tumors.
Ipsilateral loss of light touch,
vibration, and position sense
generalized below the lesion level
Below T6 only the fasciculus gracilis
is present.
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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
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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.
Contralateral loss of pain
and temperature sense
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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
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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.
Ipsilateral upper motor neurons signs
generalized below the lesion level
UMN signs
Weakness (Spastic paralysis)
Hyperreflexia (+ Babinski, clonus)
Hypertonia
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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
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Hemicord Lesion (Brown-Sequard Syndrome)
Click to animate
R
L
L1
Common causes
include
penetrating
injuries, lateral
compression from
tumors, and MS.
Build the lesion
Hemicord lesion
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
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Hemicord Lesion (Brown-Sequard Syndrome)
UMN
Click to animate
DRG
R
L
DRG
L1
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
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Thank you
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