An EMG study is used to assess the health of the nerves and muscles. Although the
test is frequently referred to as an “EMG test,” it actually is made up of two components:
electromyography (EMG) and nerve conduction studies (NCS). EMG/NCS is also commonly
known as Electrodiagnostic Testing.
Who needs an EMG/NCS test?
Patients with numbness, tingling, pain, weakness, or muscle cramping are frequently
assessed with EMG/NCS. Disorders most commonly assessed include: carpal tunnel syndrome,
ulnar neuropathy, peripheral neuropathy, radiculopathy (“pinched” nerves in the neck
or low back), sciatica, spinal stenosis and disc herniations.
What patient preparation is required prior to an EMG/NCS test?
Patients are advised not to apply any creams, lotions, or oils to their skin the
day of the test. During the test, small electrodes are attached to the arms or legs
with an adhesive. The electrodes may not attach properly if a patient has creams,
lotions, or oils on their skin. Otherwise, no other patient preparation is required.
Patients taking blood thinners or patients with pacemakers can have EMG/NCS tests
performed, but the test may be modified to accommodate these circumstances.
What is involved when having an EMG/NCS test?
Depending on the areas of the body being evaluated, the patient may be asked to change
into a gown. Before the test, a focused patient history and examination is performed
and imaging reviewed if appropriate. This evaluation helps determine which specific
nerves and muscles should be assessed with the EMG/NCS test. The findings from the
initial nerves and muscles assessed will determine which additional nerves and muscles
should be tested.
The NCS component of the test evaluates electrical signals along the nerves to the
skin or muscle. Electrodes are attached to the skin with an adhesive. A small electrical
stimulus is applied to a nerve and the electrical signal is detected at the electrodes.
An electrical waveform is produced on a computer screen. The speed, size, and shape
of the waveform are analyzed. The number of nerves tested will depend on the clinical
situation and the findings from the initial nerves tested.
The EMG component of the test evaluates the electrical signals from the muscles.
A sterile, small, thin needle electrode is inserted into different muscles. The electrical
activity is assessed when the patient contracts the muscle and when the patient has
the muscle relaxed. The electrical activity is displayed on a computer screen and
the noise produced from this electrical activity is heard from a small speaker. Visualizing
and hearing the electrical activity are both important in determining what is normal
versus abnormal. The number of muscles tested will depend on the clinical situation
and the findings for the initial muscles tested.
Is EMG/NCS painful?
For the NCS, a small electrical stimulus (shock) is applied to the nerve. This stimulus
is very brief (less than one thousandths of a second). This will feel like a small
electrical shock and the muscles may “twitch” during the shock. Otherwise NCS is
For the EMG portion of the test, a small, thin needle electrode is inserted into
different muscles. At times there may be some discomfort during testing; however
the needle can be easily moved slightly to a different area which will not cause
discomfort. It is very rare that a patient will not be able to tolerate this part
of the test.
How long does EMG/NCS take?
Testing usually takes 30-60 minutes. Afterwards, there are no patient restrictions.
When are the results available?
At Commonwealth Sport and Spine, EMG/NCS tests are performed and interpreted by a
physician board-certified in Electrodiagnostic Medicine. The EMG/NCS report is typically
ready within 24-48 hours and will be sent or faxed to the patient’s referring physician
(and other physicians if requested).