Upper motor neuron lesions occur in the cerebral cortex or brainstem and cause symptoms such as spasticity, hyperreflexia, pathological reflexes like Babinski's sign, and minimal muscle wasting. Lower motor neuron lesions occur in the spinal cord, nerve roots, or peripheral nerves and result in flaccidity, hyporeflexia, absent reflexes, fasciculations, muscle wasting, and peripheral sensory loss. The main differences between upper and lower motor neuron lesions are in the site of the lesion and the resulting muscle tone, reflexes, and patterns of weakness and sensory involvement.

1. DIFFERENCEBETWEEN
UPPERANDLOWERMOTORNEURONLESION

2.  The term Upper Motor Neuron was first introduced by
William Gowers.
 Upper Motor Neurons are found in the cerebral cortex
and the brainstem, which carry information down to
activate inter neurons and lower motor neurons which
in turn directly signal muscles to contract or relax..

3.  The Lower Motor Neurons begin in the Spinal Cord
and end in the skeletal muscles. If lower motor neurons
are lost, it leads to weakness, muscle twitching, and
muscle atrophy.

4. S.
No
CONTENTS UMN LESION LMN LESION
1. Site of the Lesion Cerebral hemisphere,
Cerebellum, brainstem,
Spinal cord
Anterior horn
cell, nerve roots,
peripheral nerves,
NMJ muscles
2. Muscle tone Spasticity-Clasp knife type
Hyper tonicity
Flaccidity-
Hypo tonicity
3 Clonus Present Absent
4. Deep Tendon
reflexes
Pathological reflexes
Hyper reflexia
Babinski’s sign Present
Hypo reflexia
Absent
5. Muscle weakness Quadriplegia, Hemiplegia,
Diplegia, Paraplegia
Proximal
weakness-
Myopathy
Distal weakness-
Neuropathy

5. S.No CONTENTS UMN LESION LMN LESION
6. Abdominal reflexes Absent Present
7 Fasciculations Absent Present
8. Sensory Loss Cortical Sensations Peripheral
sensation
9. EMG Normal nerve
conduction
Decreased
interference pattern
and firing rate
Abnormal nerve
conduction
Large motor units
Fasciculations and
fibrillations
10. Muscle wasting Minimal Present
11. Eyebrow
involvement
Sparing Involved