Lack of voluntary coordination of muscle movements with jerky, unsteady trunk motion describes which condition?

• A. Dysmetria
• B. Ataxia
• C. Dystonia
• D. Choreoathetosis

Answer: (B)

Ataxia is the lack of voluntary coordination of muscle movements, typically due to cerebellar dysfunction. The description of jerky, unsteady trunk motion reflects this incoordination, where movements are mis-timed and the trunk wobbles or jerks as you try to move. This is a hallmark of cerebellar-based movement problems and often accompanies gait instability and issues with smooth, coordinated tasks.

Dysmetria, a common feature of ataxia, is about misjudging distance or amplitude of a movement. Dystonia involves sustained or repetitive muscle contractions causing abnormal postures or twisting, not just unsteady movement. Choreoathetosis combines rapid, irregular choreic movements with slower, writhing movements. The described pattern fits ataxia best because it centers on broad incoordination and unsteady, jerky motion rather than the specific misdistance, abnormal postures, or mixed hyperkinetic movements of the other conditions.