American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

Fibrillation potentials are indeed observed in cases of muscle denervation during an electromyography (EMG) evaluation. These potentials arise as a result of increased excitability of denervated muscle fibers. When a muscle fiber loses its normal nerve supply, the lack of neurotransmitter stimulation leads to spontaneous activity within the fibers.

Fibrillation potentials are small, irregular electrical signals that indicate that the muscle fibers are still capable of generating action potentials on their own—despite the absence of the nerve typically responsible for their activation. These potentials are a hallmark finding in EMGs for discerning nerve injury or muscle denervation and can assist clinicians in making a diagnosis.

In contrast, the other types of potentials listed do not represent the same physiological response seen specifically in denervated muscles. For example, compound muscle action potentials are recorded from multiple muscle fibers and may be more indicative of communication between a healthy nerve and muscle rather than denervation. Myotonic discharges are associated with diseases like myotonia, which involve abnormal repetitive contractions of muscle fibers. Fasciculations are visible twitches of muscle fibers, usually due to irritability of the motor neuron, and are not as definitive in signaling denervation as fibrillation potentials are.