Which type of increased tone is commonly associated with Parkinson's disease?

• A. Spasticity
• B. Hypotonia
• C. Flaccidity
• D. Rigidity

Answer: (D)

In Parkinson’s disease, the increased tone that shows up is rigidity. This comes from abnormal basal ganglia signaling due to dopaminergic neuron loss, which makes muscles resistant to passive movement. The resistance is present at rest and through the range of motion and is not strongly dependent on how fast you move the limb. Clinically this can feel like a steady, continuous resistance (lead-pipe rigidity) and may be observed as a ratchety ‘cogwheel’ phenomenon when tremor interacts with rigidity. This contrasts with spasticity, which is velocity-dependent and typical of upper motor neuron lesions; and with hypotonia or flaccidity, which are decreased muscle tone.