Electromyography (EMG) – Treatment, Effects & Risks

Electromyography (EMG)

Electromyography (EMG) is a procedure that measures the electrical voltage in muscles and is used, among other things, in neurology for diagnostic purposes. The main methods are needle and surface EMG, which differ in their spatial resolution and invasiveness, among other things.

What is an electromyography?

In electromyography, an electrode measures the electrical voltage in a muscle. The electrode either penetrates the tissue (needle myography) or lies over the muscle on the [[skin] (surface myography). In a broader sense, electromyography also includes electroneurography (ENG), which deals with the measurement of electrical signals in peripheral nerves .

As a rule, the EMG first measures the electrical voltage at rest. In the case of damaged muscles, abnormalities can already be seen under certain circumstances. In addition, the resting potential serves as a baseline and thus as a reference for the comparison between resting state and activity.

Certain damage in muscle and nerve cells are associated with typical patterns in the EMG. Doctors can therefore draw conclusions about the condition of the muscle from the measurement results. In patients who suffer from a blood clotting disorder or who are taking anticoagulant medication, electromyography is usually not suitable due to the risks.

Application and function

The main field of application of electromyography in medicine is neurological diagnostics. Doctors use it, for example, to locate nerve damage and determine its extent. To do this, they can use various types of electromyography; Which method is used in an investigation depends, among other things, on the question at hand.

In addition, an EMG can help to diagnose injuries, diseases and functional disorders of the muscle and to distinguish whether a functional disorder originates in the nerve or in the muscle.

Peripheral nerves can be examined with a similar method, electroneurography (ENG) , which is also often included in electromyography. ENG can be used, for example, in the diagnosis of herniated discs when nerve roots are damaged – or of certain hereditary diseases that affect the peripheral nervous system.

But not only medicine makes use of electromyography: it can also provide additional insights in sports. For sports science, electromyography is an instrument that can be used, for example, in measurements for basic and applied research. Certain research designs in psychology and other scientific fields also use electromyography.

methods and procedures

The needle electromyogram or needle myogram derives the electrical voltage via fine needles in which the electrodes are located. The needles penetrate the muscle tissue and are therefore able to measure the signals with high spatial accuracy.

In contrast, the surface EMG uses electrodes that are stuck to the skin and from there measure the electrical voltage of the muscles. As a result, the spatial resolution of the electromyogram is lower. Medicine therefore uses it, for example, to measure the delay between a triggering stimulus and the reaction of the muscle.

In the stimulation or fatigue electromyogram, a weak electrical stimulus stimulates the muscle and the EMG records the physiological response as usual.

What does the patient have to consider?

Whether special preparation is necessary depends, among other things, on the specific objective of the examination, which is why patients should follow the instructions given by their doctor. After a needle EMG, patients should ensure that the punctures do not become inflamed or exposed to contamination.

Heavy loading of the affected muscle following a needle myogram may be avoided. In case of unexpected symptoms and complications, it is advisable to inform the attending physician.

process and implementation

Medical examinations usually use needle electromyography. A trained specialist sticks several needles into the muscle that is relevant for the diagnosis. There are sensitive measuring electrodes in the needles. They already register small electrical voltages as they occur in the human body. The needles are very thin and therefore usually do little damage to the skin and muscle. In the case of the surface electromyogram, the electrodes stick to the skin, just like in the case of an EKG.

The signals, which the electrodes in the needles or on the skin measure, run through an amplifier. A monitor makes the tension in the muscle visible as curves and shows, for example, the strength of the electrical activity and its progression over time.

The EMG curves usually resemble the representations of ECG or EEG measurements. With the help of such information, doctors can, among other things, draw conclusions about the condition of the muscle and possibly localize injuries or other damage.

Self-service or health insurance – who bears the costs?

If the EMG is used to diagnose an illness and is recognized as a procedure for this purpose, the health insurance company can cover the costs for the electromyography. In many applications in neurological diagnostics, the corresponding prerequisites are given. The practice or clinic in which the examination is to take place can tell you whether this applies in individual cases or whether a separate referral is necessary.

Risks, dangers and complications

Electromyography is usually considered a low-risk procedure because serious complications are rare. An exception are patients who suffer from hemophilia , take anticoagulant medication or have another blood clotting disorder.

The punctures can cause them to bleed and lead to complications. Whether an EMG is still necessary depends on the individual case and requires weighing up the advantages and disadvantages. In many cases, however, electromyography is contraindicated for patients with impaired blood coagulation.

In particular, stimulation myograms can be critical for patients with pacemakers . Problems can also arise with other diseases and medications taken, which is why only the responsible doctor can make a decision for the individual patient.

The punctures during needle myography can cause pain comparable to that of an injection and can last for a few days. Numbness is also possible. In rarer cases, the punctures can trigger a complex regional pain syndrome, which can manifest itself in the form of pain and muscle weakness, among other things.

Adhesive electrodes cause skin irritation in some people, which may require medical evaluation.

Dorothy Farrar

Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.

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