Clonus - The maximum hyperexcitability!
“rhythmic involuntary muscular contractions induced by the sudden passive stretching of a muscle or tendon”
- hyperactive DTR (4+)
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“rhythmic involuntary muscular contractions induced by the sudden passive stretching of a muscle or tendon”
- hyperactive DTR (4+)
#MedTwitter #neurotwitter #EndNeurophobia #tweetorials
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Electrodiagnostic
“ankle clonus soleus rectified EMG and position of the ankle are displayed superimpose. Soleus muscle activity can be seen after ankle dorsiflexion”
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“ankle clonus soleus rectified EMG and position of the ankle are displayed superimpose. Soleus muscle activity can be seen after ankle dorsiflexion”
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Frequency
variable description regarding frequency 5 – 15 Hz
- unsustained (transient, exhaustible, or abortive) clonus (≤5 beats): may be physiological
- sustained clonus (>5 beats): regarded as abnormal
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variable description regarding frequency 5 – 15 Hz
- unsustained (transient, exhaustible, or abortive) clonus (≤5 beats): may be physiological
- sustained clonus (>5 beats): regarded as abnormal
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Pseudoclonus
- psychogenic disorders
- poorly sustained and irregular in rate, rhythm and excursion
- ankle clonus; true clonus can usually be stopped by sharp passive plantar flexion of the foot or great toe while the false clonus remains unaltered.
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- psychogenic disorders
- poorly sustained and irregular in rate, rhythm and excursion
- ankle clonus; true clonus can usually be stopped by sharp passive plantar flexion of the foot or great toe while the false clonus remains unaltered.
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Pathophysiology
UMN lesions cause an ⬆️ in gamma motor neuron activity and a decrease in inhibitory interneuron (renshaw cell) activity, resulting in a state of hyperexcitability of alpha motor neurons.
New Zealand neurologist Derek Ernest Denny-Brown (1901–1981)
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UMN lesions cause an ⬆️ in gamma motor neuron activity and a decrease in inhibitory interneuron (renshaw cell) activity, resulting in a state of hyperexcitability of alpha motor neurons.
New Zealand neurologist Derek Ernest Denny-Brown (1901–1981)
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Patellar clonus
https://doi:10.1001/jamaneurol.2020.0175 via: JAMA Neurology
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https://doi:10.1001/jamaneurol.2020.0175 via: JAMA Neurology
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