Which condition is characterized by resting tremor, rigidity, akinesia, and postural instability?

Parkinson's disease is characterized by a classic triad of symptoms: resting tremor, rigidity, and akinesia (or bradykinesia), along with postural instability. These manifestations result from the degeneration of dopaminergic neurons in the substantia nigra, part of the basal ganglia, which plays a critical role in coordinating movement.

The resting tremor in Parkinson's disease is a distinct feature that occurs when the patient is at rest and often diminishes with voluntary movement. Rigidity refers to increased muscle tone leading to stiffness, while akinesia describes the slowness of movement or difficulty initiating movements. Postural instability can result in a tendency to fall, reflecting the impaired balance that accompanies the disease.

In contrast, Huntington's disease primarily involves chorea (involuntary, jerky movements) and cognitive decline and does not exhibit resting tremors or rigidity as hallmark symptoms. Multiple sclerosis can cause various neurological symptoms due to demyelination, including tremors, but these are not typically classified under the main symptoms of resting tremor and rigidity. Alzheimer's disease is characterized by memory loss and cognitive decline, rather than the motor symptoms seen in Parkinson's disease.

Thus, the specific combination of resting tremor, rigidity