UMN and LMN Lesion

What is an upper motor neuron

A neruon that originates in the brain and travels down to synapse with lower motor neurons in the spinal cord or brainstem.

What is a lower motor neuron

A neruon that travels from the spinal cord or brainstem directly to the muscle.

Where does an UMN lesion occur

Above the ant horn cell in the spinal cord, or above cranial nerve motor nuceli

Where does a LMN lesion occur

At the ant horn cell, nerve root, peripheral nerve, or neruomuscular junction.

Is atrophy seen in LMN lesion

Yes

Is atrophy seen in UMN lesion

Normal muscle bulk

What type of weakness is seen in UMN lesion

Reduced power w/ pyrimidal pattern. Extensors weaker than flexors, in arms and vice versa in legs.

What type of weakness in seen in LMN lesion

Decreased tone, flaccidity

What type of tone is seen in UMN lesion

Increased - spasticity and rigidity

What happens to DTR in UMN lesion

Hyperreflexia

What happens to DTR in LMN lesion

Reduced or absent

Are fasiculations seen with LMN lesion

Yes

Are fasiculations seen with UMN lesion

No

Is babinski/hoffmans sign present in UMN lesion

Yes

Is babinski/hoffmans sign present in LMN lesion

No

What is clonus and when is it seen

Series of involuntary, rythemic muscle contractions caused by a sudden sustained stretching of a muscle. Seen with UMN lesions.