tremor /trem″ər, trē″mər/ [L, shaking] , rhythmic, purposeless, quivering movements resulting from the involuntary alternating contraction and relaxation of opposing groups of skeletal muscles, occurring in some elderly individuals, certain families, and patients with various neurodegenerative disorders. Senile tremor is characterized by fine quick movements, especially of the hands, rhythmic head nodding, and increased trembling during purposeful movements. Familial tremor, which may be hereditary, and the tremor occurring in multiple sclerosis also increase during voluntary movement and may be intensified by anxiety, excitement, and self-consciousness. The tremors of Graves’ disease, alcoholism, mercury poisoning, and other toxicoses are usually less rhythmic. The tremor in lead poisoning often affects the lips. The fine, quick, continuous tremor present in Parkinson’s disease sometimes disappears during purposeful movements. Kinds include resting tremor, intention tremor.
