- Discussion:
- when needle is inserted into muscle or moved w/in muscle, there is a single burst of activity
that usually lasts 300 to 500 ms;
- activity is related to movement of electrode and is thought to result from mechanical stimulation
or injury of the muscle fibers;
- Increased Insertional Activity:
- increased insertional activity is found in denervated mucle or in muscle that is being reinnervated;
- insertional activity will be increased in nerve compression syndromes (
axonotmesis,
neurotmesis);
- it is also increased in
axonal neuropathies and
anterior horn disease;
- insertional activity that lasts longer than 300 to 500 ms may be an early sign of denervation and
is also found in
polymyositis, myotonic disorders, and some of the other
myopathies;
- Decreased:
- reduction of insertion activity is found after prolonged denervation when muscle fibers
have been replaced by connective tissue and with fibrosis;
