facilitation
Increase in CMAP amplitude with repetitive nerve stimulation, typically seen in presynaptic neuromuscular junction disorders.
Full Definition
Facilitation is an increase in compound muscle action potential (CMAP) amplitude observed during repetitive nerve stimulation studies, particularly at high frequencies (20-50 Hz) or following brief maximal voluntary exercise. This phenomenon occurs when presynaptic calcium accumulation enhances acetylcholine release at the neuromuscular junction. Facilitation is characteristically seen in Lambert-Eaton myasthenic syndrome and botulism, where baseline CMAP amplitudes are typically low but can increase dramatically (>100%) with high-frequency stimulation or post-exercise potentiation. This contrasts with the decremental response seen in postsynaptic disorders.
Usage
Usage note: Specify percentage increase and distinguish from pseudofacilitation due to warming.
In Context
- "High-frequency stimulation revealed marked facilitation with a 250% increase in CMAP amplitude, consistent with Lambert-Eaton syndrome." — Repetitive nerve stimulation report