EMG and nerve conduction tests: why they are done and what to expect

What is an EMG?

In everyday practice, "EMG" usually means a combined electrodiagnostic test made up of two parts:

• nerve conduction studies (NCS) – small electrodes are placed on the skin, brief electrical pulses are applied, and the speed and strength of the signal travelling along the nerve are measured;
• needle electromyography – a fine needle electrode is inserted into a muscle to record its electrical activity at rest and when you tighten it.

The two parts complement each other. Nerve conduction shows whether a nerve is affected and where, while needle EMG shows whether a muscle has lost part of its nerve supply or whether the problem lies in the muscle itself. The test is carried out by a neurologist or a physician trained in clinical neurophysiology and is part of the diagnostic work-up of many neurological conditions.

Why might you need an EMG?

Your doctor may request the test if you have:

• numbness, tingling or pain in the hand, especially at night – typical of carpal tunnel syndrome;
• leg pain, numbness or weakness from a herniated disc pressing on a nerve root (radiculopathy or sciatica);
• burning and numbness in both feet, suggesting peripheral neuropathy, for example in diabetes;
• unexplained muscle weakness, wasting, twitching or cramps;
• a suspected muscle disease (myopathy) or a problem with nerve-to-muscle signalling, such as myasthenia gravis;
• a nerve injury, to assess how severe it is and how it is recovering;
• follow-up of a known condition, or assessment before nerve release surgery.

How to prepare

Little preparation is usually needed, but a few steps help make the results accurate:

• shower on the day and do not apply creams or lotions to your skin;
• wear loose clothing that allows easy access to your arms or legs;
• if your hands or feet are cold, they may be warmed first, because temperature affects nerve conduction;
• tell the team in advance if you take blood thinners, have a pacemaker or other implanted device, or have a bleeding disorder;
• bring your referral and any previous EMG reports and scans, such as an MRI.

Do not stop any medicines unless your doctor tells you to.

What happens during the test

Nerve conduction studies

Small sticky electrodes are placed on the skin over the muscle. A handheld device placed over the nerve delivers brief pulses, which feel like a tap or a mild static shock and make the muscle twitch for a moment. The pulses are repeated at several points along the nerve.

Needle EMG

After cleaning the skin, the doctor inserts a thin, sterile, single-use needle into selected muscles. Activity is recorded at rest, and then you are asked to tense the muscle gently and then more strongly. The signals appear on a screen and are often heard as crackling sounds through a speaker. The needle is uncomfortable but usually less painful than an injection, because nothing is injected.

The whole test typically takes 30 to 60 minutes, depending on how many nerves and muscles need checking. You can return to normal activities straight away.

Risks and after-effects

EMG is a safe test. You may notice mild soreness or small bruises where the needle went in, which settle within a day or two. Infection is extremely rare because the needles are sterile and used only once. If you take anticoagulants, the doctor will decide which muscles can be tested safely. The electrical pulses are low in strength and do not damage the nerves.

What the results can show

The specialist analyses the speed and size of nerve signals and the pattern of muscle activity. Results may point to:

Importantly, EMG is not a diagnosis on its own. It is interpreted together with your symptoms, examination, blood tests and imaging. A normal result does not rule out damage to small nerve fibres, which standard EMG does not detect well.

What happens next

The written report usually goes to the doctor who requested the test, and sometimes to you as well. It lists the nerves and muscles tested, the measurements and a conclusion. Your doctor compares the findings with your symptoms and decides whether you need treatment, further tests or simply monitoring. In carpal tunnel syndrome or a trapped nerve root, EMG helps judge severity and whether surgery is worth discussing. In polyneuropathy, blood tests are used to look for the cause. The test is sometimes repeated after a few months to check nerve recovery or the effect of treatment, so keep copies of all previous reports.

When to see a doctor

See your GP or a neurologist if numbness, pain or weakness in your arms or legs lasts more than a few weeks, is getting worse, or interferes with sleep or work. Do not wait for a planned test – seek emergency care (112 in Europe) if weakness develops quickly over hours or days, if you have difficulty breathing or swallowing, sudden weakness on one side of the body or face, or loss of bladder or bowel control with back pain and numbness around the buttocks – see lower back pain.

EMG and neurological assessment abroad and in Türkiye

Some patients from Bulgaria and elsewhere in Europe have these tests at large accredited hospitals in Istanbul as part of a wider neurological or orthopaedic assessment, for example before planned surgery. If you are considering this, bring all previous results and scans, ask for a written EMG report in English, and confirm who will interpret the findings and how treatment will continue at home. Organisers such as New City Clinic in Istanbul coordinate appointments, the hospital, hotel, transfers and an interpreter. If in doubt, an independent second opinion can help.