Rigidity is commonly associated with which diagnosis?

Rigidity is commonly associated with which diagnosis?

• A. Alzheimer's disease
• B. Multiple sclerosis
• C. Parkinson's disease
• D. Amyotrophic lateral sclerosis

Answer: (C)

Rigidity as a motor sign is most characteristic of Parkinson's disease. It reflects increased muscle tone that resists passive movement, often described as lead-pipe rigidity (and sometimes cogwheel rigidity when the resistance has a sudden stop-and-go feel). This arises from basal ganglia dysfunction due to loss of dopaminergic neurons in the substantia nigra, which disrupts the balance of pathways that normally regulate movement. The result is a classic triad of resting tremor, bradykinesia, and rigidity, with the other conditions—Alzheimer's disease (primarily cognitive decline), multiple sclerosis (more commonly spasticity from demyelination), and amyotrophic lateral sclerosis (mixed upper and lower motor neuron signs including weakness)—not presenting with the same hallmark rigidity pattern.

Rigidity as a motor sign is most characteristic of Parkinson's disease. It reflects increased muscle tone that resists passive movement, often described as lead-pipe rigidity (and sometimes cogwheel rigidity when the resistance has a sudden stop-and-go feel). This arises from basal ganglia dysfunction due to loss of dopaminergic neurons in the substantia nigra, which disrupts the balance of pathways that normally regulate movement. The result is a classic triad of resting tremor, bradykinesia, and rigidity, with the other conditions—Alzheimer's disease (primarily cognitive decline), multiple sclerosis (more commonly spasticity from demyelination), and amyotrophic lateral sclerosis (mixed upper and lower motor neuron signs including weakness)—not presenting with the same hallmark rigidity pattern.