Exam

Ankle Clonus

search

Ankle Clonus, Clonus

  • Definitions
  1. Clonus
    1. Involuntary Muscle movement rapidly alternating Muscle Contraction and relaxation (typically 5-7/sec)
  2. Sustained Clonus
    1. Following persistent stimulus (e.g. ankle dorsiflexion), Clonus persists (10 beats or more)
  3. Unsustained Clonus
    1. Following persistent stimulus (e.g. ankle dorsiflexion), Clonus may occur briefly and rapidly extinguish
  • Technique
  • Ankle Clonus
  1. Patient lies supine, relaxed with knee in slight flexion
  2. Examiner grasps the foot and suddenly forces the ankle into dorsiflexion and holds the foot in that position
  • Findings
  • Abnormal Ankle Clonus
  1. Rhythmic ankle flexion and extension for at least 3 beats of Clonus before it extinguishes
  • Causes
  • Sustained Ankle Clonus
  1. Upper Motor Neuron Lesion
    1. Cerebrovascular Accident
    2. Multiple Sclerosis
    3. Cerebral Palsy
    4. Encephalopathy
  2. Other systemic conditions
    1. Liver failure
    2. Serotonin Syndrome
    3. Preeclampsia
  • References
  1. Degowin and Degowin (1987) Bedside Diagnostic Exam, Macmillan Publishing, New York, p. 818