Nerve conduction studies (NCS) and electromyography (EMG)

These investigations are generally performed to aid the diagnosis of any disorder involving the peripheral nervous system.  Any test will be explained to you before it is carried out and you will be able to ask any questions or tell us any concerns. Results of your test will be sent to referring doctor in 5 working days.

Here are some of the commonly asked questions concerning Nerve Conduction and Electromyography Studies.

What is a Nerve Conduction Study (NCS)?

It is a study of the electrical properties of nerves to see how your nerves are working.  

Why do I need an NCS?

Your GP may request this test to see how your nerves and muscles are working if you have had symptoms such as tingling, numbness or weakness in your legs, arms or face.  

The test will be performed by a Consultant Neurophysiologist, and it generally takes between 30 to 45 minutes, but on rare occasions, it may take about an hour.

How is an NCS performed?

The study is performed using a specially designed electronic device connected to a computer.  Pads or rings are placed on the skin, and you will feel a tingling or tapping sensation.  The response is then recorded from a pad placed further along the nerve.  Different nerves are tested to compare and see which, if any, are affected.

Here is the typical electrode placement for sensory studies:

Motor studies are performed by recording the response from a muscle whilst the nerve innervating (supplying) the muscle is being stimulated.

Here is the typical electrode placement for motor studies:

What is an Electromyography Study (EMG)?

This is not always necessary but may be required after the Nerve Conduction Study.  It is a study of the electrical properties of the muscles.

How is an EMG performed?

EMG is performed using a very fine disposable needle electrode that tells us the status of the nerve and muscle.  After the needle is in place you will be asked to make the muscle movement, for example by bending your arm.

Are the tests painful?

There may be slight discomfort, but most patients tolerate the tests well.   The pulses feel like a TENS machine pulse.

Are the tests safe?

There are no reported side effects.  Some patients may complain of slight tingling or tenderness after the test or in exceptional cases, may suffer slight bruising after needle examination.

Can everyone have these tests?

Yes, the tests can be performed safely on children and pregnant women.  

However, please advise the department before your appointment if you:

• Have a pacemaker
• Are taking blood-thinning tablets such as Warfarin Apixaban or any other blood-thinning tablets. You may be required to stop the medication for 24-48 hours before the EMG examination. Please contact the so that you will be informed how long to stop the medication.

Is there any complication of the NCS/EMG tests?

There is no complication of nerve conduction studies apart from discomfort at the time of examination. The needle EMG is associated with some complications such as bruising. Very rarely needle examination may be performed around the shoulder blade, chest wall and lower rib area. There is a risk of puncturing the chest wall which may lead to air escaping from the lungs in an outer cavity (pneumothorax). The risk of this happening is 1 in every 200-500 patients examined. If this happens it will cause the lung to collapse, and you may develop shortness of breath including chest pain. To treat this condition, you will require admission into the hospital.

EMG if performed when you are on a blood-thinning tablet may result in simple bruising to serious bleeding inside the muscle like compartment syndrome. The incidence of serious bleeding on blood thinning tablets is 1 in 10000. The exact incidence in those who don’t take blood-thinning is not known but it is rare.

Do I need to do anything special before my test?

No special preparation is needed but it would be helpful to do the following:

• Wear loose clothes so that the area can be easily accessed.
• Do not apply any creams; lotions are greasy substances that cause difficulty in recording signals from the nerves.
• Keep hands and feet warm by wearing gloves, socks etc. as cold hands and feet affect the test.
• Please inform us if you are a wheelchair user and need assistance in transfer to the examination couch

Who can I contact if I have any more questions?

If you have any concerns or questions about your appointment, please contact our Patient Liaison team on one of the contact details below and they will be very happy to help you:  

Telephone: 0114 250 5510

Email: enquiries@onehealth.co.uk

Address: One Health Group , 131 Psalter Lane, Sheffield, S11 8UX

Website: www.onehealth.co.uk