Which term describes a ratchety resistance to passive movement seen with rigidity?

Which term describes a ratchety resistance to passive movement seen with rigidity?

• A. Spasm
• B. Tremor
• C. Clonus
• D. Cogwheel or lead pipe

Answer: (D)

Ratchety resistance during passive movement is described as cogwheel rigidity, a characteristic way rigidity can feel in Parkinsonian syndromes. As you move the limb, the resistance comes in a series of small, jerky releases—like a cog turning—giving that ratchety sensation. A related rigidity pattern is lead-pipe rigidity, where the resistance is smooth and constant throughout the motion. The term that reflects the ratchety quality—and is often noted together with lead-pipe in descriptions of rigidity—emphasizes these two classic patterns clinicians use to describe tone. Spasm involves a sudden, intermittent increase in tone rather than a patterned ratcheting; tremor is a rhythmic oscillation of movement; clonus is a series of rhythmic contractions in response to stretch. None of those produce the characteristic ratchet-like, stepwise resistance that defines cogwheel rigidity.

Ratchety resistance during passive movement is described as cogwheel rigidity, a characteristic way rigidity can feel in Parkinsonian syndromes. As you move the limb, the resistance comes in a series of small, jerky releases—like a cog turning—giving that ratchety sensation. A related rigidity pattern is lead-pipe rigidity, where the resistance is smooth and constant throughout the motion. The term that reflects the ratchety quality—and is often noted together with lead-pipe in descriptions of rigidity—emphasizes these two classic patterns clinicians use to describe tone.

Spasm involves a sudden, intermittent increase in tone rather than a patterned ratcheting; tremor is a rhythmic oscillation of movement; clonus is a series of rhythmic contractions in response to stretch. None of those produce the characteristic ratchet-like, stepwise resistance that defines cogwheel rigidity.