Which condition is characterized by both muscle rigidity and tremors?

The condition characterized by both muscle rigidity and tremors is known as Parkinsonism. This syndrome encompasses a range of symptoms that are similar to those seen in Parkinson's disease, which is a neurodegenerative disorder. Muscle rigidity refers to the resistance of muscles to passive movement and is a hallmark feature of Parkinsonism, while tremors, often resting tremors, manifest as rhythmic oscillations of the limbs or other body parts. These symptoms arise due to the dysfunction of dopaminergic neurons in the brain, particularly in areas responsible for movement control.

In contrast, akathisia primarily involves a compelling need to be in constant motion and does not typically feature muscle rigidity or tremors. Dystonia is characterized by sustained muscle contractions, twisting, or abnormal postures, and while it can cause rigidity, it does not manifest with resting tremors. Bradykinesia refers to slowness of movement, which is another common symptom of Parkinson's disease but does not specifically include both rigidity and tremors as defining characteristics. Thus, Parkinsonism encapsulates the combination of muscle rigidity and tremors, making it the correct answer.