Neuro - UMN and LMN lesions

Question 1

Identifying neurological disorders based on presentation and examination findings:

a) Upper Motor Neuron Lesion

Answer 1

Interruption in neural pathway occurring “at a level above the anterior horn cell”

Signs:
No or slight muscle wasting
Tone - Increased (Hypertonia)
Power – weakness in all muscles but more pronounced in the upper limb abductors and extensors; lower limb abductors and flexors.
Reflexes – Increased (Hyperreflexia)

Question 2

Identifying neurological disorders based on presentation and examination findings:

a) Lower Motor Neuron Lesion

Answer 2

Interruption of the spinal reflex arc i.e. spinal motor neuron, motor root or peripheral nerve lesion.
Signs:
Muscle wasting – present
Fasciculations – may be present
Tone – usually reduced (not easily detectable)
Power – weakness in all muscles affected
Reflexes – absent or reduced