This document discusses upper and lower motor neurons and their roles in voluntary movement. It describes: - Upper motor neurons originate in the brain and spinal cord, control lower motor neurons, and are involved in voluntary movement, reflexes, muscle tone, and facial expressions. - Lower motor neurons originate in the brainstem and spinal cord, directly innervate skeletal muscles, and are the final pathway between the central nervous system and muscles. - Damage to upper motor neurons causes spasticity, hyperreflexia, pseudobulbar palsy, and weakness without atrophy. Damage to lower motor neurons causes flaccid paralysis, muscle atrophy, and hypotonia. - Brown-Sequ

1. UMN
LMN
Brown Sequard
Syndrome
Dr. Anupam Mittal
MBBS, MD
King George's Medical University, Lucknow

2. Neuroanatomy of Motor
Neurons
• The Upper Motor Neuron (UMN)-
• The cell body, lies within the motor cortex of the cerebrum, and
• The axon, forms the corticospinal tracts and corticobulbar tracts
• 1/3rd primary motor cortex + 1/3rd from the somatic sensory cortex (area
1,2,3)
• The Lower Motor Neuron (LMN)-
• Lying in the brainstem motor nuclei and the anterior horns of the spinal
cord,
• Directly innervate skeletal muscles
• The UMNs are rostral to the LMNs and exert direct or indirect supranuclear
control over the LMNs

4. Upper motor neuron control lower motor
neuron through two different pathways
Voluntary movement
of the contralateral
side
Regulate the action of motor neurons
• Involuntary movement, reflexes,
visual and auditory reflexes)
• Muscle tone
• Musculature Responsible for facial
expressions

7. Lower Motor Neuron
• All voluntary movement depend upon excitation of
lower motor neuron by upper motor neuron
• These are the only neurons that innervate the
skeletal muscle fibers,
• Function as the final common pathway, the final
link between the CNS and skeletal muscles

8. Classification of LMN
Based on the type of muscle fiber they innervate:
• Alpha motor neurons (α-MNs)
• innervate extrafusal muscle fibers,
• the most numerous type of muscle fiber and the one involved in muscle
contraction
• Gamma motor neurons (γ-MNs)
• innervate intrafusal muscle fibers,
• which together with sensory afferents compose muscle spindles
• These are part of the system for sensing body position (proprioception)

9. UPPER MOTOR NEURON LESION
• Loss Voluntary skillful movements (corticospinal)
• Babinski sign (corticospinal)
• Loss of superficial reflex (corticospinal)
• Weakness with no muscle atrophy
• Spasticity is hallmark of the UMN disease
• Spasticity is a state of sustained increase in muscle
tension in response to muscle lengthening, in
particular, with passive movements
• Hyperreflexia deep tendon reflex
• Pseudobulbar palsy is hallmark of the UMN
disorder

10. PSEUDOBULBAR PALSY
• Results from an upper motor neuron lesion to the
corticobulbar pathways in the pyramidal tract.
• It results from bilateral lesion of UMN’s of the muscles
of the tongue (XII), face (VII), speech and swallowing
(IX,X)
• Individuals with pseudobulbar palsy also demonstrate
inappropriate emotional outbursts.

11. Lower Motor Neuron Lesion
• Flaccid paralysis
• Muscle atrophy and Hypo-reflexia
• Muscle hypotonicity
• Fasciculations

12. BULBAR PALSY
• Similar disorder as psedobulbar palsy, but is caused
by lower motor neuron lesions
• It consists of LMN signs in regions innervated by
• the facial (VII),
• glossopharyngeal (IX),
• Vagus (X) and
• hypoglossal (XII

14. Brown Sequard Syndrome
Causes
How it occurs
What are the
main causes
Symptoms
What’s
happening
during it

15. • Also known as
• Transverse hemisection syndrome or
• Hemiplegia syndrome
• It's a disease when one half of the
spinal cord is injured or damaged
• that's why it's Classified as an
incomplete cord syndrome