Clinical sign | UMN syndrome | LMN syndrome |
Weakness | ‘Pyramidal’ distribution, that is, hip flexor and foot dorsiflexor predominant | Focal or multifocal, often in peripheral nerve or root distribution |
Loss of distal dexterity | Present | Absent if no sensory loss |
Slowness and simplification of movement | Present | Absent |
Poor balance responses | Present | Absent |
Fatigue | Present | Present |
Muscular atrophy | Slight or absent | Prominent in weak muscles |
Muscular tone | Increased with spasticity | Reduced in weak muscles |
Deep tendon and superficial reflexes | Tendon reflexes increased or superficial reflexes diminished | Tendon reflexes reduced or absent superficial reflexes normal or reduced |
Babinski response (and related responses) | Present | Absent |
Fasciculation | Absent | Present |
Note that these traditional criteria do not include any higher-order functional tests in the case of UMN disorders, which could distinguish frontotemporal cerebral dysfunction from limited lesions in the corticospinal tracts in the brainstem or spinal cord. Internal capsular lesions frequently involve non-corticospinal descending pathways, in addition to the corticospinal pathways themselves.
LMN, lower motor neuron; UMN, lower motor neuron.