Electromyography ( EMG ) - Causes, Symptoms and Treatment .MF .

August 12, 2017 17:52 | Instrumental

Electromyography - a diagnosis of bioelectric potentials in the muscle when excited (reduction) of muscle fibers.For the first time on a man employed electromyography in 1907 the German scientist G. Pieper.Currently electromyograph - a computer system that records biopotentials, amplifies them, calculates the amplitude, frequency and duration of the latent periods, reduces the "noise", carries out stimulation and analysis.

Register potentials produced by means of skin or needle electrodes.

skin electrodes

Needle electromyography

The signal is then amplified, processed and passed on electromyography imaging device - either on the oscilloscope to record on paper or on magnetic media - recorded electromyogram.We estimate the amplitude of muscle building vibrations.

main types electromyogram .

work muscles depends on the quality of the muscle fibers and nerves of the valuable work that conduct nerve impulses from the brain and spinal cord.In violation of the electrical activity of the mus

cles can be seen on the underlying disease with muscle pathology, determine the cause of the weakness (paralysis), muscle twitches her.

diagnostic method is harmless.Maybe a slight pain at the injection needle electrode.

Indications electromyography:

- complaints of pain and weakness in the muscles, slimming muscles, muscle spasms, muscle twitching and muscle cramps,
- suspicion of myopathy, myasthenia gravis, myotonia, amyotrophic lateral sclerosis, myoclonus, muscular dystonia, essentialtremor, Parkinson's syndrome, multiple sclerosis,
- injuries of peripheral nerves and plexus, root damage in degenerative - dystrophic spine diseases, neuropathy facial nerve neuropathy, polymyositis, tunnel syndromes
- to assess the functional state of the dynamics and effectiveness of treatment,
- localmyography held for precise injection of Botox into the spastic muscle fibers.

How is EMG

not recommended to conduct research after taking drugs (muscle relaxants, antiholinergetikov) and physical therapy, smoking and caffeine (coffee, chocolate, tea, cola).If you have a pacemaker, you are taking anticoagulants, you need to be sure to say about this doctor.

A study in a relaxed position - lying down or sitting.First, remove the potentials at rest, then by slow muscle strain.The electrodes record the common cutaneous indications with muscles (interference, global EMG), Needle introduced in different parts of the muscle, different muscles (EMG local).

In the study of electrical stimulation of muscles used.Cutaneous electrodes - a pair of metal plates up to 10.5 mm, which are superimposed at a distance of 20 - 25 mm from each other.For electrostimulation use surface stimulating electrodes.We study the symmetrical muscles are functionally related to each other, for a maximum voltage.

procedure can last anywhere from 15minutes to an hour depending on the objectives of the survey.

At rest, with maximum relaxation biopotentials are not registered.

Explanation EMG

At the beginning of muscle contraction amplitude oscillations appear 100 - 150 mV, with a maximum reduction of - 1000 - 3000 mV (depending on the person's age, physical development).

In the primary muscle disease - myositis, progressive muscular dystrophy recorded decrease of the oscillation amplitude.Reduced amplitude correlates respectively of gravity muscle injury - in severe cases up to 20-150 mV at maximum excitation, while slowly progressive course of the disease in the initial stages - to 500mkV.When the local normal EMG recorded the total number of action potentials, but the amplitude and duration of their lowered.This is due to reduction in the number of normal muscle fibers capable of reduction.To compensate for the defect in the body muscle activation occurs more muscles.This leads to intensification of interference and the number of polyphase (multiphase) potentials.

When lesions of peripheral nerve trunks (genetic, metabolic (including diabetes), toxic (including alcoholic) polyneuropathy) recorded slowing oscillations uneven single potentials in amplitude and frequency to global EMG.The general background EMG activity is characterized by low amplitude.On the local polyphase EMG recorded action potentials with almost normal characteristics.With the death of the majority of nerve fibers gradually suppressed bioelectrical activity of muscles to complete the bioelectrical silence - no potentials.

When spinal amyotrophy - hereditary diseases of the spinal cord motor neurons with muscle weakness, muscle twitching on the local EMG recorded spontaneous activity in the form of fibrillation potentials, sharp waves, increase in amplitude.Global EMG registers alone spontaneous bioelectric activity (fasciculations 100 - 400 mV), and at a maximum voltage of high-amplitude rhythmic potential - "the rhythm of the stockade."

In myotonic syndromes - a group of hereditary diseases with delayed muscle relaxation (dystrophic myotonia, myotonia Thomsen, Becker, Eulenburg ...) muscles easily excitable and EMG recorded myotonic aftereffect: low-amplitude, high-frequency electrical activity for a long time after the cessation of voluntary musclereduction with slow fading away.On the local EMG myotonia is registered with increased excitability of muscle fibers - a series of the same amplitude of action potentials in response to the introduction of the needle electrode.

In myasthenic syndromes - disorders of the nervous - muscular synaptic transmission in the EMG recorded increasing amplitude reduction caused by the muscle-building at repeated rhythmic stimulation.

in parkinsonism, essential tremor - pathology nadsegmentarnyhvozdeystvy on motor neurons of the anterior horns of the spinal, interest extrapyramidal system on a global EMG recorded rhythmically repeating "volleys" fusiform increase the oscillation amplitude and the subsequent decline.The frequency and duration of the "spindle" varies depending on the localization of the pathological process.
for more accurate diagnosis using collaborative study - electromyography with electroneurogram - electroneurogram.

neurologist Kobzev SV