Final answer:
Upper motoneuron lesions do not typically present with atrophy. They are characterized by spasticity and other signs such as muscle weakness, strong deep tendon reflexes, decreased control of movement, pronator drift, a positive Babinski sign, and the clasp-knife response.
Step-by-step explanation:
Upper motoneuron lesions typically do not present with atrophy. A characteristic feature of upper motor neuron (UMN) lesions is spasticity, which is an excess contraction in resistance to stretch and results in hyperflexia.
Muscle weakness, strong deep tendon reflexes, decreased control of movement or slowness, pronator drift, a positive Babinski sign, and the clasp-knife response are other signs that suggest a UMN lesion.