Which type of muscle atrophy results from injury or disease of the nerve that connects to the muscle?

• A. Physiologic
• B. Pathologic
• C. Neurologic
• D. Traumatic

Answer: (C)

Neurologic atrophy happens when the nerve supplying the muscle is injured or diseased, interrupting the neural input that keeps the muscle active. Without that nerve signal, the motor units lose stimulation and trophic support, so the muscle fibers shrink and the muscle weakens. This is distinct from atrophy due to aging or disuse alone (physiologic), which doesn’t involve nerve damage, and from atrophy caused by systemic disease or broad tissue pathology (pathologic). The key idea is that the problem lies with the nerve-to-muscle connection, not just the muscle itself.