EMG (Electromyography): Purpose, Procedure & Results

Introduction

Electromyography (EMG) is a vital diagnostic tool used by neurologists and other medical professionals to evaluate the health of muscles & the nerve cells that control them. This comprehensive article will explore what EMG is, its purpose, the procedure involved, and what the results can indicate. Whether you’re preparing for an EMG test or simply curious about this medical procedure, this article will provide you with a thorough understanding of electromyography.

What is Electromyography (EMG)?

EMG is an essential diagnostic procedure that evaluates the condition of muscles & the nerve cells that control these muscles, known as motor neurons. These motor neurons carry electrical signals that cause muscles to contract & relax. An EMG converts these signals into graphs or numbers.

Doctors generally perform the EMG test when a patient shows symptoms of muscle or nerve disorder or conditions affecting the connection between nerves and muscles.

It’s worth noting that some doctors may refer to electromyography as an electrodiagnostic exam. The test is often performed alongside a nerve conduction study (NCS). NCS measures the electrical current that flows through a nerve before it reaches a muscle.

What is the Purpose of the Electromyography Test?

The primary purpose of an EMG is to help diagnose a wide range of neuromuscular disorders. Your doctor may recommend an EMG if you’re experiencing symptoms that could indicate a muscle or nerve problem, such as:

• Tingling or numbness along the course of the nerve
• Muscle weakness
• Muscle pain or cramps
  • Paralysis
• Involuntary muscle twitching (or tics)

The outcomes of an EMG can help your doctor discover the underlying cause of these symptoms. Some conditions that an EMG can help diagnose include:

• Muscle disorders, such as muscular dystrophy
• Conditions affecting the ability of motor neurons to send electrical signals to muscles, like myasthenia gravis
• Radiculopathies (pinched nerves)
• Peripheral nerve disorders that affect nerves outside the spinal cord, such as carpal tunnel syndrome
• Nerve disorders like amyotrophic lateral sclerosis (ALS)

EMG in motor neuron disease is particularly valuable, as it can help detect the characteristic changes in electrical activity associated with conditions like ALS.

What is the Procedure for an EMG Test?

The EMG procedure consists of two main components: the nerve conduction study & the needle EMG. The following is a step-by-step breakdown of what you can expect during an EMG test:

Preparation: 

Before the test, you should:

• Avoid smoking for at least 3 hours before the procedure
• Bathe or shower to remove oils from your skin, but don’t apply lotions or creams afterwards
• Wear comfortable attire that doesn’t obstruct the area being evaluated
• Inform your doctor about any medications you’re taking and any medical conditions you have, especially bleeding disorders or if you have a pacemaker or implantable defibrillator

The Procedure:

• You’ll be asked to lie on an examination table or sit in a reclined chair.
• The nerve conduction study is performed first:

1. 1. The doctor will place small sensors called surface electrodes on your skin.
   2. These electrodes assess how well your motor neurons communicate with your muscles.
   3. You may feel a brief tingling sensation during this part of the test.

• After the nerve conduction study, the needle EMG is performed:

1. 1. The diagnostic team cleans the affected area with an antiseptic.
   2. A thin needle electrode is inserted directly into the muscle tissue.
   3. You may feel some discomfort or pain during needle insertion.
   4. The needle records electrical activity in your muscle when it’s at rest and when you contract it.
   5. Your doctor may ask you to contract and relax the muscle multiple times during the test.

• The electrodes deliver tiny electrical signals to your nerves during both parts of the procedure.
• A computer translates these signals into graphs or numerical values for your doctor to interpret.

The entire EMG procedure typically takes between 30 and 60 minutes.

What Do the Results of an EMG Test Indicate?

After the EMG test, your doctor will analyse the results to look for any abnormalities in your muscle or nerve function. Here’s what different results might indicate:

Normal Results:

• No electrical activity in muscles at rest
• Steady increase in electrical activity when a muscle contracts
• Rapid decrease in electrical activity when a muscle relaxes

Abnormal Results:

• Electrical activity in a resting muscle could indicate:
  • A muscle disorder
  • A disorder affecting the nerves connecting to the muscle
  • Inflammation caused by injury
• Abnormal electrical activity during muscle contraction might suggest:
  • A herniated disc
  • A nerve disorder like ALS
  • Carpal tunnel syndrome

It’s important to note that EMG results alone are not usually sufficient to make a definitive diagnosis. Your doctor will consider these results alongside your medical history, physical examination, and other test results to determine the underlying reason for your symptoms.

Conclusion

Electromyography is a valuable diagnostic tool that provides crucial information about the health and function of muscles and motor neurons. While the procedure may cause some discomfort, it’s generally safe and can provide essential insights into a wide range of neuromuscular disorders. If you’re experiencing symptoms of muscle or nerve problems, an EMG test and other diagnostic procedures can help your doctor arrive at the best treatment approach for your condition.

Still have questions? Book an appointment with a doctor or feel free to browse through our FAQs section.

Frequently Asked Questions

What is the level of discomfort during an EMG test?

The level of discomfort during an EMG test can vary from person to person. The nerve conduction study portion typically causes minimal discomfort, often described as a brief tingling sensation. The needle EMG can be more uncomfortable, as it includes inserting a thin needle into the muscle. Some people describe it as a pinching or burning sensation. While it can be uncomfortable, most people find the pain tolerable. If you’re particularly concerned about pain, discuss this with your doctor beforehand, as they may be able to suggest ways to minimise discomfort.

How much time does an EMG test usually require?

An EMG test typically takes between 30 and 60 minutes to complete. However, the exact duration can vary and depends on the number of nerves and muscles being tested and the specific information your doctor is looking for. In some cases, if multiple areas need to be examined, the test might take longer. 

What happens when EMG is positive?

A positive EMG indicates abnormal muscle or nerve function, suggesting a neuromuscular disorder.

Is EMG better than MRI?

EMG and MRI serve different purposes; EMG assesses nerve and muscle function, while MRI provides detailed images of soft tissues.

What is the age limit for EMG?

There is no specific age limit for EMG, as it can be performed on patients of all ages based on clinical need.