EXTRAPYRAMIDAL TRACTS & MOTOR NEURON LESIONS

1. EXTRAPYRAMIDAL TRACTS&MOTOR NEURON LESIONS Dr. SHAIKH MUJEEB AHMED Assistant professor AL MAAREFA COLLEGE

2. 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

4. Overview of Motor System

5. CNS influence the activity of skeletal muscle through two sets of neuron • Upper motor neuron • Lower motor neuron

6. PYRAMIDAL TRACTS • corticospinal tract • EXTRAPYRAMIDAL TRACTS- • Reticulospinal Olivospinal • Vestibulospinal • Tectospinal • Rubrospinal tract • Corticobulbar tract • Corticorubral tract

7. 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

8. Cerebral Cortex SC RN Mid Brain RFP Corticospinal Tract VN Pons Tectospinal Tract RFM Rubrospinal Tract Medulla Vestibulospinal Tract Reticulospinal Tract Sp. cord

10. Position of tracts in the spinal cord

11. Function of Extrapyramidal tract • Cortinuclearfibre 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.

12. ROLE OF EXTRAPYRAMIDAL SYSTEM ATONIC ExtraPyramidal system Pyramidal system

13. Nerve pathways

14. Descending Pathways

15. Extrapyramidal disorders • Lesions in the extrapyramidal tract cause various types of diskinesias or disorders of involuntary movement • Parkinsonism • Chorea • Hemiballism • Athetosis • DystoniaTardivedyskinesia

16. 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 • 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.

18. UPPER AND LOWER MOTOR NEURON

20. 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

21. 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.

23. 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

24. 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.

25. 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

26. 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.

27. 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

28. 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.

29. 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

30. 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

31. 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