Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What would an EMG examination reveal in a patient with post-polio syndrome?

1. Evident nerve root dysfunction

2. Signs of anterior horn disease

3. Decreased muscle response

4. Purely sensory nerve damage

The correct answer is: Signs of anterior horn disease

In a patient with post-polio syndrome, an EMG examination would reveal signs of anterior horn disease. This condition reflects the pathology associated with previous poliovirus infection, which primarily affects the motor neurons in the anterior horn of the spinal cord. As a result of the initial viral infection, some motor neurons are permanently damaged, leading to muscle weakness and atrophy. Over time, survivors may develop post-polio syndrome, characterized by new muscle weakness, muscle fatigue, and joint pain. The EMG can detect changes indicative of ongoing denervation and reinnervation processes in the affected muscles, demonstrating the impact on the anterior horn cells rather than on peripheral nerves or sensory pathways. While the other options might present symptoms in different neuromuscular disorders, they do not accurately reflect the specific EMG findings associated with post-polio syndrome. For instance, evident nerve root dysfunction is more aligned with conditions that affect nerve roots directly rather than the anterior horn cells. Similarly, decreased muscle response could be seen in a variety of neuromuscular diseases, and purely sensory nerve damage pertains more to sensory neuropathies, which are not characteristic of post-polio syndrome.