What do fibrillation potentials commonly indicate when observed during an EMG?

Fibrillation potentials are abnormal electrical activities observed in muscle fibers during electromyography (EMG) testing. When these potentials are detected, they typically indicate the presence of denervated muscle fibers. Denervation occurs when a nerve that supplies the muscle is damaged or cut, leading to muscle fiber instability, which results in fibrillation potentials.

In a healthy muscle, the electrical activity observed would consist of normal motor unit action potentials, which reflect intact nerve supply and normal muscle function. The appearance of fibrillation potentials signals that the nerve supply to the muscle has been compromised, which is critical information in diagnosing neuromuscular disorders, nerve injuries, or conditions that affect peripheral nerves. Understanding that these potentials point towards denervation helps clinicians assess the underlying causes of muscle weakness, atrophy, or other neuromuscular symptoms.