EMG & NCS

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EMG & NCS help diagnose neuromuscular disorders.

EMG & NCS are safe–with appropriate precautions.

Electromyography (EMG) and nerve conduction studies (NCS) are 2 types of procedures that are almost always performed together because they have closely interrelated purposes: To aid in diagnosis of neuromuscular disorders.  Both muscles and nerves use of electricity to perform their normal functions.  EMG and NCS both measure of electricity from the body to identify any abnormal function of muscles, nerves, or the connections between them (synapses).  Although both procedures are extremely safe, Dr. Rossen takes appropriate precautions following literature guidelines (see AANEM position statement on risks and appropriate precautions for these procedures).  There are no contraindications with pregnant patients.  Some additional precautions are necessary for patients on anticoagulation, with skin infection, or with implanted cardiac electrical devices, brain or spine stimulators.  These situations are discussed in more detail below.

how long does it take?

What should I wear?

Please come to your appointment for EMG and NCS wearing loose fitting clothes.  If the studies are focusing on legs, please wear appropriate underwear or shorts.  Please bathe or shower before the procedure and avoid any cream or oil on the skin is these substances on the skin can reduce the accuracy of the data gathered, especially with NCS.  The appointment takes about an hour but to be safe, please leave at least 90 minutes in your schedule.

 Are EMG & NCS uncomfortable?

They can be, but most people do okay.

you can always stop.

EMG and/or NCS can be uncomfortable.  Every individual experiences the “surge of current” or “shock” of the electric signal differently.  Every individual experiences the small needle insertion of EMG differently.  Most individuals tolerate both procedures without significant problem.  The purpose of EMG and NCS is to gather valuable information toward diagnosis that might help management of symptoms.  However, Dr. Rossen and his staff are aware of the potential discomfort and try to minimize this while gathering this valuable information.  If you are too uncomfortable, please immediately communicate with Dr. Rossen or his staff.  The procedure will be appropriately altered, or, if necessary, terminated. 

EMG in more detail…

A small needle measures electricity in muscle

EMG employs a very small sterilized needle inserted through the skin into a muscle, to measure the natural electric signals coming from that muscle.  As each muscle is in close contact with nerve branches, the signals provide information on both muscle and nerve.  The needle is attached to a wire which transmits the measured signal to a computer that calculates signal characteristics from which abnormalities of muscle and/or nerve may be identified.  EMG is safe for patients on medication for anticoagulation (e.g., Coumadin) although standard of care in this situation is to avoid the study of certain muscles to maximize safety.  EMG is also safe from the point of view of infection control as long as standard infection control measures are in place.  Standard of care is to avoid parts of the body where there might be active skin infection. 

NCS in more detail…

Electrodes measure electricity through nerve branches

NCS uses 2 sets of electrodes that are taped or touched to the skin.  One set of electrodes transmits a very short (100 or several 100s milliseconds) electrical signal to your skin.  The other set, touching the skin several inches away, measures the electricity of that signal that has travelled along those several inches.  The electrodes are strategically placed so that the signal mostly travels through part of a nerve and perhaps part of a muscle (all lying beneath the skin between the 2 sets of electrodes).  The second set of electrodes then transmits the measured signal to a computer that calculates signal characteristics from which any abnormality that might exist can be identified.  NCS is essentially safe in patients with implanted cardiac pacemakers or defibrillators, deep brain stimulators or spine stimulators as long as additional precautions are taken: NCS is not performed in regions close to stimulator or stimulator wires.  NCS is not performed if someone has an electrical device with external wires.  

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