Features of Lower Motor Neuron (LMN) and Upper Motor Neuron (UMN) Weakness
| LMN | UMN | |
|---|---|---|
| Tone | Normal/decreased | Spastic |
| Deep tendon reflexes | Supressed/lost | Exaggerated |
| Plantar response | Flexor/mute | Extensor |
| Fasciculations | May be present | Absent |
| Atrophy | Pronounced (if axonal process) | Slight (reflecting disuse) |
| Distribution of weakness | Individual muscles may be affected, bilaterally innervated muscles can be involved | Groups of muscles affected, ‘pyramidal’ pattern;* bilaterally innervated muscles spared |