What is a characteristic sign of fibrillations in muscles?

• A. Visible contractions of all muscle fibers
• B. Individual muscle fiber contraction
• C. Immediate recovery of nerve function
• D. Severe muscle atrophy

Answer: (B)

Fibrillations in muscles are characterized by individual muscle fiber contractions. This phenomenon occurs due to the spontaneous and irregular electrical activity in denervated muscle fibers, which can be detected during an electromyography (EMG) test. When a muscle fiber is damaged or has lost its nerve supply, it may start to contract independently, leading to the sensation or detection of fibrillations. This is distinct from the visible contractions of all muscle fibers, which typically occur in healthy muscle function or a coordinated contraction scenario.

The lack of cohesive movement among muscle fibers, as evident in fibrillation, indicates localized issues that are not reflective of the overall muscle condition—contrasting with options that suggest immediate recovery of nerve function or severe muscle atrophy. Understanding fibrillations is crucial in differentiating between various neuromuscular disorders, as it highlights individual muscle fiber disturbances rather than a general muscular response.