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. 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).

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

EXTRAPYRAMIDAL 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

Vestibulospinal Tract Sp. cord Medulla Pons Mid Brain Cerebral Cortex Corticospinal Tract Tectospinal Tract Rubrospinal Tract Vestibulospinal Tract Reticulospinal Tract 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.

ROLE OF EXTRAPYRAMIDAL SYSTEM ATONIC ExtraPyramidal system Pyramidal system

Nerve pathways Descending Tracts Tract 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.

Descending Pathways Pathway Upper limb Lower limb Cortico/-pyramidal This Tract functions to modulate the activity of Alpha or Gamma Motor Neurons as directed by the Motor Cortex. Rubro-spinal Stimulates flexors Reticulo-spinal Medullary inhibits extensors and excites flexors Pontine excites extensors and inhibits flexors (Generally upper limb) Vestibulo-spinal Doesn’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

Components of motor neurons Upper motor neuron (corticospinal & corticobulbar). Starts from motor cortex and ends in Cranial nerve nucleus (corticobulbar). Anterior horn of spinal cord in opposite side(corticospinal tracts). Lower Motor Neuron Starts 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

Right Dorsal Column Lesion Click to animate DRG R L L1 Dorsal column lesion Ipsilateral loss of light touch, vibration, and position sense generalized below the lesion level Below T6 only the fasciculus gracilis is present. Common causes include MS, penetrating injuries, and compression from tumors.

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

Right Lateral Spinothalamic Tract Lesion Click to animate DRG R L L1 Lateral spinothalamic tract lesion Contralateral loss of pain and temperature sense Common causes include MS, penetrating injuries, and compression from tumors.

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

Right Lateral Corticospinal Tract Lesion UMN Click to animate R L L1 Lateral corticospinal tract lesion Ipsilateral upper motor neurons signs generalized below the lesion level UMN signs Weakness (Spastic paralysis) Hyperreflexia (+ Babinski, clonus) Hypertonia Common causes include penetrating injuries, lateral compression from tumors, and MS.

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

Hemicord Lesion (Brown-Sequard Syndrome) Click to animate R L L1 Hemicord lesion Common causes include penetrating injuries, lateral compression from tumors, and MS. 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 Build the lesion

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