Repetitive Nerve Stimulation (RNS) and Single-Fibre Electromyography (SFEMG)

What are Repetitive Nerve Stimulation (RNS) and Single-Fibre Electromyography (SFEMG)?

RNS and SFEMG are specialised tests that measures how well signals are transmitted from your nerves to your muscles.

Your doctor may recommend this test to: 

• Evaluate double vision or drooping eyelids.
• Assess for neuromuscular transmission disorders such as myasthenia gravis.

This list is non-exhaustive.

How should I prepare for RNS and SFEMG?

Before the day of test

• Not required to fast
• Continue with your regular diet and medications (unless instructed differently by your doctor).
• Please inform your doctor if you have an implanted electronic device, such as a heart pacemaker, defibrillator, intracranial device or neurostimulator.

On the day of test

• Do not apply lotion on the face.
• Inform our staff if you are on anti-coagulant medications (blood-thinners) such as warfarin, heparin, apixaban, dabigatran, rivaroxaban.
• Please also inform us if you previously had Botox injections.

How are RNS and SFEMG performed?

RNS is performed by a neurotechnologist and will take approximately 15 minutes.

• This test is usually done while you are lying down on the bed.
• Electrode patches (sticky pads) are placed on the skin overlying the muscle of the nerve being tested in the face, neck and/or upper limb.
• A stimulator is placed on the skin to stimulate the nerve at various points. You will feel brief, mild electric sensations over the stimulation points, which may cause discomfort, but it is safe.
• The electrical activity in the nerve is detected by the electrodes and recorded.
• For accurate test results, try to remain still, unless otherwise instructed. You may be asked to move your limbs during the test.
• Once this test is done, further testing with SFEMG may be required. If SFEMG is not required, the electrodes are removed, and the skin is cleaned.
• A detailed report will be sent to your doctor within two weeks. Your doctor will discuss the findings with you at your next appointment.

SFEMG is performed by a trained neurologist and can take approximately 30-45 minutes.

• This test is usually done while you are lying down on the bed.
• Electrode patches (sticky pads) are placed on the skin overlying the muscle of the nerve being tested, usually near the cheek or forehead.
• The skin is disinfected with an alcohol swab.
• A stimulator is placed on the skin to stimulate the nerve. You will feel brief, twitches of the eyelid or forehead, which may cause discomfort, but it is safe.
• A thin, disposable sterile needle is inserted into the muscle(s). You may feel slight discomfort during this process.
• The procedurist will guide you on what to do during the process.
• The electrical signals in the muscle are recorded by the needle. The needle may be moved to a few different positions to collect measurements.
• Once the test is done, the needle is removed, and any bleeding is compressed. You can go home after. 
• You may experience some minor bruising. It is normal for your muscles to feel sore after the test, but this should improve within a few days. If you experience severe pain, swelling, or persistent bleeding, please inform your doctor or the neurodiagnostic laboratory performing the test.
• A detailed report will be sent to your doctor within two weeks. Your doctor will discuss the findings with you at your next appointment.

Frequently Asked Questions about RNS and SFEMG

Is the test safe?

The test is generally safe, with low risk as:

• They are routinely performed.
• Needles used are much thinner than vaccination or blood test needles.
• The neurologist (doctor) and neurotechnologist will be with you throughout the process. If you feel unwell, please inform the neurologist or the neurotechnologist. 

Can I use Medisave to pay for this test?

This test may be claimable under:

• Flexi-MediSave for Seniors; or
• Outpatient scans for diagnosis or treatment of a medical condition. 

Please refer to the Ministry of Health's Outpatient Care page for the latest claim limits and eligibility criteria.

The information is correct as of July 2026 and subject to revisions without notice.
Content adapted from NNI Neurodiagnostic Laboratory (NDL), NNI@TTSH.