Electrodiagnostic Testing: EMG Flashcards
what is EMG
tests electrical activity of muscles
what does EMG assist in diagnosing
conditions that interfere with muscular contraction
muscular dystrophy
myasthenia gravis
peripheral neuropathies
amyotrophic lateral sclerosis
ruptured spinal disc
what is the EMG procedure and what is it doing
testing muscle at rest (fasciculations, fibrillations) and during contraction with small, wire-like needle inserted into the muscle belly
what is a MUAP
motor unit action potential
summed electrical activity of all muscle fibers activated within the motor unit
what does normal muscle activity look like at rest?
should be silence - healthy muscle at rest is electrically silent when the needle electrode is not moving
what is normal insertional activity
50-200 ms
if you have decreased normal insertional activity what could that mean
loss of muscle fibers
have also been noted in metabolic disorders
if you have increased normal insertional activity what could that mean
associated with neuropathic or myopathic disorders
if you have prolonged insertional activity what could that mean
post acute denervation
inflammatory muscle disorders
muscular dystrophy
what is normal spontaneous activity
MEPPs - mid end plate potentials
EPPs - end plate potentials
EPSs - end plate spikes
if electrical activity other than MEPPs and EPPs in the muscle at rest is present, what could that indicate?
neuropathy or myopathy
what is fibrillation, and also positive sharp waves, associated with
single muscle fiber that is degenerating
LMN problem btw anterior horn cell to the peripheral nerve
also could be present with myopathies and dx of NMJ
what is a fasciculation
spontaneous, repetitive, twitch-like contractions of the examined muscle at rest
when is a fasciculation typically seen
dx involving alpha motor neurons
chronic conditions
what is a complex repetitive discharge
polyphasic high frequency waveforms that are fixed in amplitude, consistent discharge rate, non-specific
“machine gun”
