Spasticity (upper motor neuron signs)

What it is

Spasticity is increased muscle tone and stiffness, often with exaggerated reflexes, resulting from damage to the upper motor neuron pathways in the spinal cord. A syrinx can cause spasticity, which often affects the legs.

Understanding Spasticity (upper motor neuron signs)

The spinal cord carries descending pathways (upper motor neurons) that control movement and regulate muscle tone. When a syrinx damages these pathways, the result can be spasticity — muscles that are stiff and resistant to movement, with brisk reflexes and sometimes other "upper motor neuron signs." Because these pathways travel through the cord to supply the legs, spasticity from a cervical syrinx often affects the legs (in addition to the hand weakness and wasting from damage to the local motor cells). Spasticity can affect walking and movement. As with other deficits, treatment of the syrinx may halt progression, though established effects can persist. Understanding spasticity clarifies a motor effect of cord involvement and its typical distribution in syringomyelia.

Why it matters

Understanding spasticity helps families see how a syrinx damaging spinal cord pathways can cause stiffness and increased tone, often in the legs, affecting movement and walking.