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1. alternate involuntary muscular contraction and relaxation in rapid succession.
2. a continuous rhythmic reflex tremor initiated by the spinal cord below an area of spinal cord injury, set in motion by reflex testing.
ankle clonus (foot clonus) a series of abnormal reflex movements of the foot, induced by sudden dorsiflexion, causing alternate contraction and relaxation of the triceps surae muscle.
toe clonus abnormal rhythmic contraction of the great toe, induced by sudden passive extension of its first phalanx.
wrist clonus spasmodic contraction of the hand muscles, induced by forcibly extending the hand at the wrist.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
a rhythmic contraction of the calf muscles following a sudden passive dorsiflexion of the foot, the leg being semiflexed.
Farlex Partner Medical Dictionary © Farlex 2012
ankle clonusA rhythmical, sustained series of flexion movements at the ankle. This is produced in people with damage to the nerve pathways in the spinal cord or brain (an upper motor neurone lesion), by a deliberate rapid, stretching of the ACHILLES TENDON, by forcibly flexing the foot. The spinal reflex arc is intact but the normal control on it, from above, is defective.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005