clonus : sign of upper motor neuron

Clonus

•      Clonus is a series of involuntary, rhythmic, muscular contractions & relaxations.

•      Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cases is, accompanied by spasticity (another form of hyperexcitability).

•      Clonus is most commonly found at the ankle, specifically with a dorsiflexion/plantarflexion movement (up and down).

•      Some case studies have also reported clonus in the finger, toe, and laterally in the ankle (as opposed to the typical up and down motion).

•      Ankle (medial gastrocnemius)

•      Patella (knee cap)

•      Triceps surae

•      Biceps brachii

•      Causes :

•      Clonus is typically seen in people with cerebral palsy, stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy

•      Clonus has also appeared after ingesting potent serotonergic drugs, where ingestion strongly predicts imminent serotonin toxicity (serotonin syndrome). 

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