Upper versus Lower Motor Neuron Lesion

Question 1

Paralysis - Upper Motor Neuron Lesion

Answer 1

present (spastic)

Question 2

Paralysis - Lower Motor Neuron Lesion

Answer 2

present (flaccid)

Question 3

Tone - Upper Motor Neuron Lesion

Answer 3

increased*

Question 4

Tone - Lower Motor Neuron Lesion

Answer 4

decreased

Question 5

Reflexes - Upper Motor Neuron Lesion

Answer 5

increased with clonus

Question 6

Reflexes - Lower Motor Neuron Lesion

Answer 6

decreased

Question 7

Atrophy - Upper Motor Neuron Lesion

Answer 7

absent

Question 8

Atrophy - Lower Motor Neuron Lesion

Answer 8

present

Question 9

Fasciculation - Upper Motor Neuron Lesion

Answer 9

absent

Question 10

Fasciculation - Lower Neuron Lesion

Answer 10

present

Question 11

Babinski / Hoffman - Upper Motor Neuron Lesion

Answer 11

present

Question 12

Babinski / Hoffman - Lower Motor Neuron Lesion

Answer 12

absent

Question 13

Note

Answer 13

the increase tone and spasticity seen in a patient with an upper motor neuron lesion is a result of loss of the cortical inhibition of the spinal cord reflexes carried by the lateral corticospinal tract. This inhibition is thought to be mediated through the Renshaw cell which is an interneuron that has an inhibitory effect on the lower motor neuron located in the anterior horn in the spinal cord. Removal of this inhibition will result in increase in muscle tone.