Physical Therapy Assistant Practice Exam

Which sign is defined by cyclical, spasmodic alternation of muscle contraction in response to sustained stretch, indicative of upper motor neuron disorders?

1. Fasciculation

2. Clonus

3. Tremors

4. Bradykinesia

The correct answer is: Clonus

The sign characterized by cyclical, spasmodic alternation of muscle contraction in response to a sustained stretch, particularly linked with upper motor neuron disorders, is clonus. Clonus occurs when a muscle is stretched beyond its capacity, triggering a rapid series of involuntary contractions and relaxations. This phenomenon is a direct result of dysfunction in the central nervous system, often seen in conditions such as multiple sclerosis, stroke, or spinal cord injury. Clonus is particularly significant because it provides insight into neurological conditions affecting motor control. It serves as an important clinical sign for healthcare providers to assess and evaluate a patient's neurological status. Related phenomena, such as fasciculations, tremors, and bradykinesia, do not exhibit the specific cyclical pattern or elicitation by sustained muscle stretch in the same way as clonus does. This distinction reinforces clonus as the correct answer, emphasizing its role in identifying upper motor neuron pathology.