Electromyography (EMG) at Brighton Hospital

What is an EMG?

An EMG (electromyography) is a test that checks the health of your muscles and the nerves that control them, sometimes called motor neurons. It measures the electrical signals your muscles produce, both at rest and when you use them, to see how well your muscles and nerves are working together.

Why might I need an EMG?

Your doctor might recommend an EMG if you have symptoms such as numbness, tingling or a 'pins and needles' feeling, muscle weakness, cramping or spasms, or difficulty with everyday tasks like walking, buttoning clothes or holding objects.

What are the benefits of having one?

An EMG can help pinpoint the location and extent of nerve or muscle damage, and can give an indication of whether the problem is likely to improve. This helps your doctor confirm a diagnosis, rule out other causes, and plan the right treatment for you.

Are there different parts to the test?

An EMG usually has 2 parts, often done in the same appointment:

• A nerve conduction study: This is where small electrical impulses are sent through electrodes on your skin to see how well signals travel along your nerves
• A needle exam: This is where a fine needle electrode is inserted into one or more muscles to record their electrical activity, both at rest and while you contract them.

In some cases, your doctor may only need one part rather than both.

How do I prepare for an EMG?

Bathe or shower beforehand and wear comfortable, loose-fitting clothing. Avoid using any creams, lotions or perfume on your skin on the day of the test, as these can affect the results.

Tell the healthcare professional carrying out the test if you take blood-thinning medicines, or if you have a pacemaker, implanted defibrillator, or a joint replacement. These generally don't cause any problems, and you shouldn't stop taking any medicines without checking with your doctor first.

In some cases, you may also be asked to avoid smoking or caffeine for 2 to 3 hours beforehand, as these can interfere with the results.

What happens during the test?

An EMG usually follows these steps:

1. You'll sit or lie down for the test
2. If you're having a nerve conduction study first, small electrode stickers are placed on your skin, and brief electrical impulses, which feel like a small shock, are sent through your nerves
3. For the needle exam, the person carrying out the test finds the muscle they need to check, then inserts a small needle electrode into it, which may feel uncomfortable
4. You'll be asked to relax, and then to use the muscle in certain ways, such as flexing or lifting a limb, while a machine records and displays the electrical activity
5. This is repeated for each muscle being tested, usually taking 1 to 2 minutes per muscle.

The whole test usually takes between 30 and 90 minutes, depending on how many muscles and nerves need checking.

What happens after the test?

Once enough information has been recorded, the needles are removed and the test is finished. A report with the results is usually sent to the doctor who requested the test.

Your muscles may feel a little sore or tender afterwards, and you might notice some minor bruising where the needles went in. Some sources suggest this usually settles within an hour or two, though others note it can occasionally last a few days.

What are the risks?

EMG is generally very safe, and complications are rare. The needles used are sterile, for single use only, and are thrown away straight after your test, so there's no risk of infection being passed between patients.

If you take blood-thinning medicines, there's a slightly higher chance of minor bleeding or bruising where the needles were inserted. Contact your doctor if you have bleeding that won't stop, severe pain, or signs of infection such as redness, warmth, swelling or a fever.