Clonus Reflex
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Purpose[edit | edit source]
Clonus is a rhythmic, oscillating, stretch reflex. The cause is related to lesions in upper motor neurons and is generally accompanied by hyperreflexia. Therefore, clonus is used as part of the neurological physical exam to assess the status of a patient’s nervous system. Clonus of the ankle results in repeated dorsiflexion of the ankle in response to brisk dorsiflexion of the foot. The test helps in differentiating between the involvement of the central nervous and peripheral nervous system.[1]
Technique[edit | edit source]
The technique is performed without equipment[1]. The clonus reaction can be elicited in the same manner as eliciting a muscle stretch reflex, which involves tapping the joint's tendon when it is relaxed, often at ninety degrees of flexion. It can be evaluated by briskly dorsiflexing the foot.
This is a simple procedure. The patient lies in a relaxed supine position. The physiotherapist slightly flexes the leg to be examined at the knee and with the other hand gently moves the ankle a couple of times in dorsiflexion and plantarflexion before rapidly dorsiflexing the ankle. The therapist holds the ankle in dorsiflexion. The initial brisk dorsiflexion and sustained pressure can be done with slight eversion of the foot. A positive Clonus sign is recorded when the examiner feels and sees the oscillations against this pressure.[2]
- Rhythm and number of beats can be appreciated.
- Each beat will be felt as a plantarflexion followed by a relaxation. The first beat is the longest, with decreasing duration of beats until the fourth beat, after which the beat frequency becomes equivalent from one to the next.
- Frequency of clonus: 5-8 Hz and the average period of oscillations of the ankle clonus is approximately 160–200 ms with plantar flexion comprising 45% of the period and dorsiflexion 55% of the period. Literature suggests that the duration of the dorsiflexion around 88.63±10.83 ms, and the duration of the plantarflexion 71.75±6.73 ms.[3]
- According to the National Institute of Neurological Disorders and Stroke (NINDS)[4], the deep tendon reflexes are graded on a scale from 0 to 4. Clonus is graded as grade 4+. If clonus is greater than 10 beats, it is considered "sustained clonus," which is sometimes denoted as a "5" or just documented as a rating of "4".
Evidence[edit | edit source]
Provide the evidence for this technique here
Resources[edit | edit source]
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References[edit | edit source]
- ↑ 1.0 1.1 Zimmerman B, Hubbard JB. Clonus.
- ↑ Fundamentals of Tests and Measures for the Physical Therapist Assistant. Chapter 9 Neuromuscular examination. Stacie J. Fruth, Carol Fawcett
- ↑ Boyraz I, Uysal H, Koc B, Sarman H. Clonus: definition, mechanism, treatment. Med Glas (Zenica). 2015 Jan 5;12(1):19-26.
- ↑ Rodriguez-Beato FY, De Jesus O. Physiology, Deep Tendon Reflexes. StatPearls [Internet]. 2020 Aug 27.
