Neurology Book


Ankle Clonus

Aka: Ankle Clonus, Clonus
  1. 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
  2. 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
  3. Findings: Abnormal Ankle Clonus
    1. Rhythmic ankle flexion and extension for at least 3 beats of Clonus before it extinguishes
  4. 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
  5. References
    1. Degowin and Degowin (1987) Bedside Diagnostic Exam, Macmillan Publishing, New York, p. 818

Clonus (C0009024)

Definition (NCI) A form of involuntary muscular movement characterized by alternating contractions and relaxation in rapid succession. In the context of reflex testing, the ability to elicit clonus indicates injury to the nerve tracts above the point at which the reflex was initiated.
Concepts Sign or Symptom (T184)
SnomedCT 36649002
Italian Clono
Japanese 間代, カンダイ, カンタイ
Czech Klonus
English clonus, Clonus, Clonus (finding)
Hungarian Clonus
Portuguese Clonus
Spanish Clonus, clonospasmo, clonus (hallazgo), clonus, clono (hallazgo), clono
Dutch clonus
French Clonus
German Klonus
Derived from the NIH UMLS (Unified Medical Language System)

Ankle clonus (C0238651)

Concepts Finding (T033)
SnomedCT 39055007
English ankle clonus, Ankle clonus, Foot clonus, Ankle clonus (finding)
Spanish clonus del pie, clonus del tobillo (hallazgo), clonus del tobillo, clono del tobillo (hallazgo), clono del tobillo
Derived from the NIH UMLS (Unified Medical Language System)

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