clonus
Pronunciation: KLO-nus
A rhythmic, involuntary muscle contraction characterized by alternating muscle contractions and relaxations, typically indicating upper motor neuron dysfunction.
Full Definition
Clonus is a neurological sign characterized by involuntary, rhythmic, oscillatory muscle contractions that occur in response to a sudden stretch of the muscle. It manifests as a series of rapid, alternating muscle contractions and relaxations that continue as long as the stretch is maintained. Clonus is most commonly observed at the ankle (ankle clonus) and knee (patellar clonus) but can occur in other muscle groups. This phenomenon indicates upper motor neuron dysfunction and is associated with increased muscle tone and hyperreflexia. Clonus is commonly seen in conditions such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The presence and intensity of clonus can impact functional movement and may require management through positioning, stretching, antispastic medications, or other interventions. Assessment of clonus is part of routine neurological examination in neurorehabilitation settings.
Usage
Usage note: Distinguish from tremor by its rhythmic, stretch-induced nature; specify location and sustainability.
In Context
- "Sustained ankle clonus was elicited during examination, indicating significant upper motor neuron involvement requiring antispastic intervention." — Neurological examination documentation