Upper and Lower motor neuron lesions

Upper and Lower Motor Neuron Lesions

1. Upper & Lower Motor Neuron lesions Prepared by: Anish Dhakal MBBS 3 rd Year [email protected]

2. Objectives To define Upper motor neurons and Lower motor neurons To describe and differentiate between Upper and Lower motor neuron lesions

3. Lower Motor Neurons: Ventral horn of spinal cord and in cranial nerve nuclei in brain stem Integral motor component of the spinal reflexes Upper Motor Neurons: Cerebral cortex and brain stem Direct the activity of lower motor neurons A least two neuron pathway needed for skeletal muscle contraction

4. Lesions of the corticospinal (Pyramidal) tracts Babinski sign: Present in Newborns: ( Incomplete myelination) Inability to suppress usual withdrawal reflex

5. UMN lesions(pyramidal) Muscle weakness Loss of superficial abdominal reflex Loss of cremasteric reflex Absence of voluntary fine skilled movements

6. Clinical significance of level of decussation Variable ipsilateral or contralateral motor weakness based on the level of corticospinal tract lesion

7. Lesions of the extrapyramidal tracts Severe paralysis Spasticity Exaggerated deep muscle reflex

8. Upper motoneurons provide descending control over the reflexes Results in hyperactive muscle stretch reflexes (tendon jerks & Clonus) (Upper motor neurons have Net inhibitory effect on muscle stretch reflexes)

9. Clasp knife reflex Oversensitive Golgi tendon organs (loss of inhibitory commands from UMN)

10. Lower motor neuron lesions Flaccid paralysis Loss of reflexes Muscular contracture Reaction of degeneration

11. Lower motor neuron lesions Muscular fasciculation & fibrillations (denervation super sensitivity) Atrophy secondary to denervation of LMN (Neither stretch reflex nor voluntary contraction) In UMN lesions, can still be contracted by stretch reflexes Disuse atrophy may be evident

12. Possible Motor lesion sites (clinical significance)

13. UMN & LMN Lesions Differences

14. THANK YOU