Which condition is characterized by involuntary muscle contractions?

Dystonia is characterized by involuntary muscle contractions that lead to abnormal movements and postures. These contractions can affect various parts of the body, causing twisting, repetitive movements, or abnormal positions. Dystonia can occur in isolation or as part of other neurological conditions.

In contrast, Parkinson's disease, while it does involve muscular issues such as tremors and rigidity, is primarily related to the degeneration of dopamine-producing neurons leading to a distinct set of symptoms including bradykinesia (slowness of movement) rather than solely involuntary contractions. Multiple sclerosis is a demyelinating disease that can result in a variety of neurological symptoms, including muscle weakness, but the muscle contractions are not typically the defining feature. Hemiplegia involves paralysis on one side of the body usually due to a stroke or brain injury, but it is not characterized by involuntary muscle contractions.

Thus, dystonia is the most accurate condition to describe involuntary muscle contractions.