extrapyramidal tracts & motor neuron lesions
DESCRIPTION
EXTRAPYRAMIDAL TRACTS & MOTOR NEURON LESIONS. Dr. SHAIKH MUJEEB AHMED Assistant professor AL MAAREFA COLLEGE. Learning Objectives. At the end of this lecture you should be able to: List the extrapyramidal tracts. Summarize the functions of extrapyramidal tracts. - PowerPoint PPT PresentationTRANSCRIPT
EXTRAPYRAMIDAL TRACTS&
MOTOR NEURON LESIONS
Dr. SHAIKH MUJEEB AHMEDAssistant professor
AL MAAREFA COLLEGE
Learning Objectives
At the end of this lecture you should be able to:• List the extrapyramidal tracts.• Summarize the functions of extrapyramidal tracts.• describe the signs and symptoms caused by a lesion of the
spinal cord (fasciculus gracilis and fasciculus cuneatus, lateral corticospinal tract, and lateral spinothalamic tract).
3
Overview of Motor System
Corticospinal tracts
Corticobulbar tracts
Bulbospinal tracts
Overview of Motor System
CNS influence the activity of skeletal muscle through two sets of neuron
• Upper motor neuron
• Lower motor neuron
PYRAMIDAL TRACTS •corticospinal tract
EXTRAPYRAMIDAL TRACTS-•Reticulospinal Olivospinal
•Vestibulospinal
•Tectospinal
•Rubrospinal tract
•Corticobulbar tract
•Corticorubral tract
Extrapyramidal tracts
• Definition: Extrapyramidal tracts are those motor pathways which may act as the alternative route for volitional impulses and which form the platform on which pyramidal system works skillfully Integrated at various level from cerebral cortex to spinal cord
• Cortical region controlling these tracts are area 8 and 6
Sp. c
ord
Med
ulla
Pons
Mid
Bra
inCerebral Cortex
Corti
cosp
inal
Tra
ct
Tect
ospi
nal T
ract
Rubr
ospi
nal T
ract
Vesti
bulo
spin
al T
ract
Retic
ulos
pina
l Tra
ct
SC RN
VN
RFM
RFP
Position of tracts in the spinal cord
Function of Extrapyramidal tract
• Cortinuclear fibre control movement of eyeball.• Other tract responsible for tone, posture(R.S. TRACT),
visiospinal reflex(T.S TRACT), equilibrium(V.S. TRACT) Control complex movement( co-ordinated movement)
• Exerts tonic inhibitory control over lower centers• Carry volitional impulse when pyramidal tract damage • The extrapyramidal system is responsible for
sustained postures, resting tone and patterned movements.
ATONIC ExtraPyramidal system
Pyramidal system
ROLE OF EXTRAPYRAMIDAL SYSTEM
Descending TractsTract Signal function
Corticospinal (pyramidal) Fine voluntary motor control of the limbs. The pathway also controls voluntary body posture
adjustments.
Rubrospinal Involved in involuntary adjustment of arm position in response to balance information; support of the body.
Reticulospinal (1) Pontine Regulates various involuntary motor activities and assists in balance (leg extensors). Some pattern
movements e.g. stepping
(2) Medullary Inhibits firing of spinal and cranial motor neurons, control of antigravity muscles.
Vestibulospinal (1) Medial It is responsible for adjusting posture to maintain balance (neck muscles).
(2) Lateral It is responsible for adjusting posture to maintain balance (body/lower limb).
Tectospinal Controls head and eye movements, Involved in involuntary adjustment of head position in response to
visual information.
Nerve pathways
Descending Pathways
Pathway Upper limb Lower limb
Cortico/-pyramidalThis Tract functions to modulate the activity of Alpha or Gamma Motor Neurons as directed by the Motor Cortex.
Rubro-spinal Stimulates flexors
Reticulo-spinalMedullary inhibits extensors and excites flexorsPontine excites extensors and inhibits flexors (Generally upper limb)
Vestibulo-spinalDoesn’t affect upper limbs but helps position head and neck in response to body tilting (medial)
Stimulates extensors (lateral)
Tecto-spinal Control of head, neck and eye movements.
Extrapyramidal disorders
• Lesions in the extrapyramidal tract cause various types of diskinesias or disorders of involuntary movement
• Parkinsonism • Chorea • Hemiballism • Athetosis • Dystonia Tardive dyskinesia
Parkinsonism
• Degeneration of extrapyramidal tract Characterized by
• Rigidity • Bradykinesia.• Tremors and • Postural deficits
17
Components of motor neurons
• Upper motor neuron (corticospinal & corticobulbar).
Starts from motor cortex and ends in 1. Cranial nerve nucleus (corticobulbar).2. Anterior horn of spinal cord in opposite
side(corticospinal tracts).• Lower Motor NeuronStarts from anterior horn of spinal cord and ends in
appropriate muscle of the same side.eg. All peripheral motor nerves.
UPPER AND LOWER MOTOR NEURON
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.
• Tendon reflexes increased. Clonus often present.
• Superficial reflexes diminished or modified. Abdominal reflex absent. Babinski’s sign +ve, Increased jaw jerk.
• Tendon reflexes diminished or absent.
• Superficial reflexes often unaltered.
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
R L
Right Dorsal Column Lesion
Dorsal column lesionIpsilateral loss of light touch, vibration, and position sensegeneralized below the lesion level
Below T6 only the fasciculus gracilis is present.
R LDRG
L1
Common causes include MS, penetrating injuries, and compression from tumors.
Click to animate
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
Lesion of the right lateral spinothalamic tract at L1 produces what impairment?
R L
R LDRG
Lateral spinothalamic tract lesionContralateral loss of pain and temperature sense
Right Lateral Spinothalamic Tract Lesion
L1
Common causes include MS, penetrating injuries, and compression from tumors.
Click to animate
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
R L
R L
UMN
Lateral corticospinal tract lesionIpsilateral upper motor neurons signsgeneralized below the lesion level
UMN signsWeakness (Spastic paralysis)Hyperreflexia (+ Babinski, clonus)Hypertonia
Right Lateral Corticospinal Tract Lesion
L1
Common causes include penetrating injuries, lateral compression from tumors, and MS.
Click to animate
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
Complete transection of the right half the spinal cord (Hemicord or Brown-Sequard syndrome) at L1 produces what impairments?
R L
R L
Hemicord Lesion (Brown-Sequard Syndrome)
Dorsal column lesionIpsilateral loss of light touch, vibration, and position sense
Lateral corticospinal tract lesionIpsilateral upper motor neurons signs
Lateral spinothalamic tract lesionContralateral loss of pain and temperature sense
Hemicord lesion
Build the lesion
L1
Common causes include penetrating injuries, lateral compression from tumors, and MS.
Click to animate
Hemicord Lesion (Brown-Sequard Syndrome)
Dorsal column lesionIpsilateral loss of light touch, vibration, and position sense
Lateral corticospinal tract lesionIpsilateral upper motor neurons signs
Lateral spinothalamic tract lesionContralateral loss of pain and temperature sense
UMN
Hemicord lesion
R L DRGDRG
L1
Click to animate