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What are upper and lower motor neurons?
- Upper and lower motor neurons control the voluntary movements.
- Upper motor neurons are located mainly in the primary motor and premotor areas of cerebrum.
- Lower motor neurons are located in the motor nuclei of the cranial nerves in the brainstem and anterior horn of spinal cord.
What are the differences between the upper and lower motor neuron lesions?
Following are the differences between the upper and lower motor neuron lesions:
| Features | Upper motor neuron paralysis (UMN ) | Lower motor neuron paralysis (LMN) |
|---|---|---|
| Paralysis type | Spastic | Flaccid |
| Muscle tone | Increased | Decreased |
| Muscle atrophy | Absent | Present |
| Tendon reflexes | Exaggerated | Diminished |
| Babinski’s sign | Present | Absent |
| Affected side | Usually Contralateral | Ipsilateral |
What is Babinski’s Sign?
Babinski’s sign: In case of upper motor neuron lesion,on scratching the lateral aspect of plantar surface of foot, the great toe is dorsiflexed and other toes are fanned out. This is called +ve Babinski’s sign.
In normal individuals all toes are planterflexed on scratching the lateral aspect of sole of foot.
