What does the presence of spontaneous fibrillation potentials in a diagnostic EMG suggest for a patient who injured their ulnar nerve?

The presence of spontaneous fibrillation potentials observed during a diagnostic electromyography (EMG) indicates that there has been a disruption in the normal functioning of the motor unit, specifically suggesting that denervation has occurred. Fibrillation potentials arise from muscle fibers that have lost their neural connections and are no longer receiving adequate innervation due to nerve injury. This condition is a direct consequence of damage to the motor axon or a severe insult to the nerve, leading to muscle denervation.

In the context of ulnar nerve injury, the identification of these potentials confirms that the muscle fibers are reacting to the loss of their nerve supply, signifying an acute or subacute phase of denervation. While the other options refer to different states of nerve and muscle recovery, they do not pertain to the immediate effects seen in the presence of fibrillation potentials. Therefore, the finding aligns closely with the interpretation of denervation as the appropriate clinical observation in this scenario.