jitter
The variability in neuromuscular transmission time measured between action potentials from the same motor unit in single-fiber EMG.
Full Definition
Jitter is a measure of the variability in neuromuscular transmission measured during single-fiber EMG (SFEMG). It represents the time variability between action potentials from two muscle fibers belonging to the same motor unit, recorded on consecutive discharges. Normal jitter values are well-established for different muscles and age groups. Increased jitter indicates impaired neuromuscular transmission and is the most sensitive measure of neuromuscular junction disorders. Jitter can be measured during voluntary activation or with electrical stimulation of the nerve.
Usage
Usage note: Always report as microseconds (μs) and compare to age-appropriate normal values.
In Context
- "Single-fiber EMG revealed increased jitter in 45% of fiber pairs, with 12% showing intermittent blocking." — SFEMG study report