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Ankle clonus. Clonus is a set of involuntary and rhythmic muscular contractions and 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). [1]
Clonus results due to an increased motor neuron excitation (decreased action potential threshold) and is common in muscles with long conduction delays, such as the long reflex tracts found in distal muscle groups. [7] Clonus is commonly seen in the ankle but may exist in other distal structures as well, such as the knee or spine. [8]
exaggerated deep tendon reflexes including spasticity, and clonus (a series of involuntary rapid muscle contractions) Such signs are collectively termed the "upper motor neuron syndrome". Affected muscles typically show multiple signs, with severity depending on the degree of damage and other factors that influence motor control. In ...
Spasticity, a velocity-dependent change in muscle tone; Clasp-knife response where initial higher resistance to movement is followed by a lesser resistance; Babinski sign is present, where the big toe is raised (extended) rather than curled downwards (flexed) upon appropriate stimulation of the sole of the foot. The presence of the Babinski ...
Any spinal cord lesions, be it traumatic, neoplastic, pyogenic, vascular above the level of S1 can cause clonus. This is because of the spasticity caused by the UMN type of injury causing hyperreflexia and clonus. Some other causes of clonus are Meningitis; Tetanus; CJD; Cerebral palsy; Multiple sclerosis; Syringomyelia; Pre-eclampsia
Spasticity can be in the form of the clasp-knife response, in which there is increased resistance only at the beginning or at the end of the movement. Rigidity can be of the leadpipe type, in which there is resistance throughout to passive movement, or it may be of cogwheel type, in which the resistance to passive movement is in a jerky manner.
Hypertonia is a term sometimes used synonymously with spasticity and rigidity in the literature surrounding damage to the central nervous system, namely upper motor neuron lesions. [1] Impaired ability of damaged motor neurons to regulate descending pathways gives rise to disordered spinal reflexes , increased excitability of muscle spindles ...
In medicine, the adjective spastic refers to an alteration in muscle tone affected by the medical condition spasticity, which is a well-known symptomatic phenomenon seen in patients with a wide range of central neurological disorders, including spinal cord injury, cerebral palsy (for example, spastic diplegia), stroke, amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS), [1] as ...