Fibrillations


- See: EMG Menu:

- Discussions:
    - fibrillations are action potentials that arise spontaneously from single muscle fibers;
    - these usually occur rhythmically and are though to be due oscillations of the resting membrane potential in denervated muscles;
    - are typically biphasic or triphasic waveforms that are distinguished from end plate potentials by their initial positive phase and high pitched repetitive click;
    - fibrillations & positive sharp waves are found in denervated muscles, but may not appear for three to five weeks after the nerve lesion;
    - seen most often seen in neurologic lesions affecting motorneurons, spinal roots, plexus, or peripheral nerves;
    - remain until nerve becomes reinnervated or the nerve becomes fibrotic;
    - fibrillation potentials alone are not diagnostic of denervation, because they occur in primary muscle diseases such as polymyositis and muscular dystrophy;

- Fasiculation Potentials:
    - fasciculation potentials are caused by the spontaneous discharges of group of muscle fibers representing a whole or part of motor unit, usually producing
           a visible twitching in the muscle;
    - fasciculation potentials most often occur in disease of anterior horn cells;
    - commonly occur in:
          - ALS;
          - progressive spinal muscular atrophy;
          - polio;
          - syringomyelia



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, September 12, 2011 12:38 pm