Upper vs Lower Motor Neurone Lesions

Question 1

What is meant by an upper motor neurone lesion?

Answer 1

Brain or spinal cord lesion

Question 2

What is meant by a lower motor neurone lesion?

Answer 2

Nerve roots, peripheral nerves, neuromuscular junction or muscle

Question 3

On inspection what differentiates UMN to LMN?

Answer 3

LMN:
>Wasting and fasciculation of muscles

UMN:
>No fasciculation or signification wasting

Question 4

What is different when comparing tone in a UMN to LMN lesion?

Answer 4

UMN lesion:
>Increased tone (spasticity or rigidity)
>+/- ankle clonus

LMN lesion:
>Decreased tone (hypotonia) or normal

Question 5

What is different when comparing power in a UMN to LMN lesion?

Answer 5

UMN lesion:
>Pyramidal pattern of weakness: extensors weaker than flexors in arm and vice versa in legs

LMN lesions:
>Different patterns of weakness depending on cause (e.g. proximal weakness in muscle disease or distal weakness in peripheral neuropathy)

Question 6

What is different when comparing reflexes in an UMN to LMN lesion?

Answer 6

UMN lesion:
>Exaggerated or brisk (hyperreflexia)

LMN lesion:
>Reduced or absent (hyporeflexia or areflexia)

Question 7

What is different when comparing plantar reflexes in UMN to LMN lesion?

Answer 7

UMN reflex:
>Upgoing/extensor (Babinski positive)

LMN reflex:
>Normal (downgoing flexor) or no movement