Final answer:
If nerve damage occurs in a patient's right arm, muscle atrophy caused by disuse can be expected over time. If the patient's arm muscles retain tone yet voluntary movement is lacking, it likely indicates an upper motor neuron lesion, which affects motor control but preserves muscle tone initially.
Step-by-step explanation:
When a patient has suffered nerve damage in the right arm, the expectation is that the muscles in that arm may undergo several changes. The muscles may initially retain their tone, but over time they can weaken due to lack of neural stimulation.
This can eventually lead to muscle atrophy, which is the wasting away of muscle mass from disuse. Given the scenario that the patient cannot move the arm voluntarily despite the muscles having tone, the damage is most likely associated with the upper motor neuron (UMN). This is because UMN damage typically results in spasticity and preserved muscle tone, at least initially, as opposed to lower motor neuron (LMN) damage, which results in flaccid paralysis and decreased muscle tone.
Signs of UMN lesion include difficulty in controlling the speed, strength, and accuracy of muscle movements (spasticity), strong deep tendon reflexes, exaggerated reflexes (hyperreflexia), and abnormal reflexes such as the Babinski sign. The presence of muscle tone with an inability to move the arm voluntarily usually indicates damage to the neuron pathways that travel from the brain to the spinal cord, affecting voluntary movement while leaving some reflexive, involuntary nervous system functions intact.