Which EMG finding is associated with denervation?

• A. Denervation causes increased nerve conduction velocity
• B. Denervation causes other electrical charges to occur that can be detected by needle EMG
• C. EMG shows no changes after denervation
• D. Denervation is invisible on EMG

Answer: (B)

When a muscle loses its nerve supply, the muscle membrane becomes unstable and can fire spontaneously. Needle EMG can pick up these spontaneous discharges even when the person is at rest. These abnormal potentials—often described as spontaneous activity such as fibrillation potentials and positive sharp waves—are classic signs that denervation has occurred.

That’s why the finding described as “other electrical charges to occur that can be detected by needle EMG” best captures what EMG shows in denervation: spontaneous, abnormal potentials that reflect the unstable resting membrane of denervated muscle fibers.

The other statements aren’t consistent with denervation findings: denervation does not cause increased nerve conduction velocity; EMG does reveal changes after denervation; and denervation is not invisible on EMG.