MUPS
Also written as: MUPS — Motor Unit Action Potentials
Motor unit action potentials with increased duration, amplitude, and phases, indicating chronic neurogenic changes. A key electrodiagnostic finding in motor neuron diseases and chronic denervation.
Full Definition
Motor unit action potentials (MUPs or MUAPs) are the electrical waveforms generated by motor units during voluntary muscle contraction. In normal muscle, these potentials have typical duration, amplitude, and phase characteristics. In chronic neurogenic conditions, surviving motor neurons sprout new axon branches to reinnervate orphaned muscle fibers, creating enlarged motor units. This reinnervation process produces MUPs with increased duration (reflecting the larger territory), increased amplitude (from more muscle fibers), and increased complexity (polyphasic morphology). These changes are hallmarks of chronic denervation and reinnervation, commonly seen in motor neuron disease, radiculopathy, and peripheral neuropathy.
Usage
Usage note: Can be abbreviated as MUPS or MUAPs. Use the full form on first mention in formal reports.
In Context
- "The MUPs showed increased duration and amplitude consistent with chronic reinnervation." — EMG interpretation
- "Polyphasic MUPs were noted in the distribution of the L5 nerve root." — Electrodiagnostic report