Final answer:
UMN lesions are characterized by muscle weakness, strong deep tendon reflexes, and other signs of upper motor neuron damage. Examples include spasticity, pronator drift, and the clasp-knife response. Diseases such as cerebral palsy, multiple sclerosis, and strokes can cause UMN lesions.
Step-by-step explanation:
UMN lesions refer to damage to the upper motor neurons in the motor system. Examples of UMN lesions include muscle weakness, strong deep tendon reflexes, decreased control of movement or slowness, pronator drift, a positive Babinski sign, spasticity, and the clasp-knife response. Spasticity is an excess contraction in resistance to stretch, resulting in hyperlexia. The clasp-knife response occurs when the patient initially resists movement, but then releases, and the joint quickly flexes.
Some diseases that can cause UMN lesions include cerebral palsy, multiple sclerosis (MS), and strokes.
In contrast, lower motor neuron (LMN) lesions result in flaccid paralysis, loss of muscle tone, and compromised or lost reflexes.