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Hypertonia, clonus , & spasticity
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What exactly is the difference between hypertonia, clonus , and/ or spasticity? Are the above terms all related and or to spasticity ?
Tone is the resistance of muscles to passive stretch or elongation, basically the amount of tension a muscle has at rest. Normal tone is high enough to resist the effects of gravity in both posture and movement yet low enough to allow freedom of movement
Hypertonia is resistance to passive movement, it is not dependent on velocity, can be with or without spasticity.
Clonus is a reflex that is a spasmodic alternation of muscular contraction and relaxation., usually seen in the calf muscle reaction when the foot is sharply bent upwards towards the thigh and held in mid position
Spasticity is an increase in resistance to sudden , passive movement and IS velocity dependent. The faster the passive movement the stronger the resistance.
As you can see from the definitions, the terms can be related, but are not interchangeable and not dependented on one another. Hypertonicity can be related to spasticity, but hypertonicity can be present without spasticity. The presence of clonus can be a sign of neurologic problems but alone is not enough for diagnostic purposes. Perisistant clonus can interfere with putting shoes on and can be stopped generally by putting the calf muscle on a end range stretch. Spasticity is directly related to the speed of the stretch placed on the muscle.
I hope this helps you understand these terms better.
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