Tremor

Tremor is an involuntary, roughly rhythmic muscle contraction and relaxation that produces oscillating or twitching movement in one or more parts of the body, most often the hands, though it can also affect the arms, eyes, face, head, vocal cords, trunk, and legs. It is the most common involuntary movement disorder, and in many people it is not a disease in its own right but a symptom of an underlying neurological condition. This generic symptom is distinct from Essential Tremor, a specific, named disease that is the most common of more than twenty recognized tremor types; Essential Tremor typically begins after age forty, can worsen gradually over time, runs in families with about a fifty percent chance of inheritance from an affected parent, and unlike tremor caused by conditions such as Parkinson's disease, carries no other associated underlying pathology of its own.