Neurology physical examination on Instagram: "Clonus is a neurological sign that indicates hyperexcitability of the stretch reflexes, usually associated with an upper motor neuron (UMN) lesion. Key Points: Definition: Clonus is a series of involuntary, rhythmic, muscular contractions and relaxations, often triggered by sudden stretching of a muscle. Mechanism: It results from loss of descending inhibitory control from the brain to the spinal cord, leading to overactive stretch reflexes. Common S