Jiggle Factor
A quantitative measure of neuromuscular transmission variability in single-fiber electromyography, calculated from consecutive discharge intervals. Used to assess neuromuscular junction stability.
Full Definition
The jiggle factor is a statistical measure used in single-fiber electromyography (SFEMG) to quantify the variability of neuromuscular transmission. It is calculated as the mean of consecutive differences (MCD) of interspike intervals between action potentials from two muscle fibers innervated by the same motor neuron. The jiggle factor provides an alternative to jitter measurement when the latter cannot be reliably calculated, particularly in cases of severe neuromuscular transmission defects or blocking. Normal jiggle factor values are typically less than 30-40 microseconds, depending on the muscle studied. Elevated jiggle factor indicates neuromuscular junction dysfunction and is useful in diagnosing myasthenia gravis and other neuromuscular transmission disorders.
Usage
Usage note: Always specify the reference value range when reporting jiggle factor measurements.
In Context
- "The jiggle factor was markedly increased at 85 microseconds, indicating impaired neuromuscular transmission." — Single-fiber EMG report
- "When jitter could not be calculated due to blocking, the jiggle factor provided valuable diagnostic information." — SFEMG interpretation