Final answer:
Upper motoneuron lesions can cause spastic paralysis due to the interruption of signals that control muscle movement.
Step-by-step explanation:
Upper motoneuron lesions can cause spastic paralysis. This is because upper motoneuron lesions result in damage to the pathways that connect the brain to the spinal cord.
As a result, there is an interruption of the signals that control muscle movement, leading to a loss of voluntary muscle control. Spastic paralysis is characterized by increased muscle tone, strong deep tendon reflexes, and exaggerated muscle contractions in response to stimuli.