CNS- planters decrease or down meaning
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CNS planters mnemonic upper lower motor neuron signs decrease
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Now I have enough to give a complete answer. The question is about the plantar reflex in the CNS context, specifically what "down" or "decreased/downgoing" means.
Plantar Reflex (CNS) - "Down" Meaning
In neurology, the plantar reflex is one of the key signs used to distinguish Upper Motor Neuron (UMN) from Lower Motor Neuron (LMN) lesions.
What "Plantar DOWN" (Flexor Response) Means
Down = Normal = Flexor plantar response
- When the lateral sole of the foot is stroked, all toes curl/flex downward
- This is the normal response in healthy adults
- It means the corticospinal (pyramidal) tract is intact
- Indicates no UMN lesion
What "Plantar UP" (Extensor Response = Babinski Sign) Means
Up = Abnormal = Extensor plantar response (Babinski sign)
- The big toe dorsiflexes (goes UP) and the other toes fan outward
- This is pathological in adults
- Indicates an UMN lesion - damage to the corticospinal tract in the brain or spinal cord
- Seen in: stroke, brain tumor, MS, spinal cord injury, etc.
Quick UMN vs LMN Comparison Table
| Feature | UMN Lesion (CNS) | LMN Lesion |
|---|---|---|
| Plantar reflex | UP (Babinski +) | DOWN (normal/absent) |
| Tone | Increased (spastic) | Decreased (flaccid) |
| Deep tendon reflexes | Increased (hyperreflexia) | Decreased/absent |
| Muscle wasting | Minimal | Prominent |
| Fasciculations | Absent | Present |
| Weakness | Pyramidal pattern | Diffuse/focal |
Summary
"Plantars down" = toes flex downward = normal finding = intact corticospinal tract "Plantars up" = big toe goes up (Babinski) = abnormal = UMN/CNS lesion
So "plantar down" is actually the good/normal sign. When someone says "plantars are down" on CNS exam, it means the pyramidal tract is functioning normally and there is no UMN lesion at that level.
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