Carmen J. Placido Jr. R. EEG/EP T.
Coordinator, Neurodiagnostic Lab
Chester County Hospital; West Chester, PA
Published: April 2, 2012
Patients can often become anxious or uncertain when their doctors order medical testing, especially when the test or procedure is less familiar. Electroencephalography and Electromyography -- part of the medical field known as "Neurodiagnostics" -- are two such relatively unfamiliar diagnostic procedures.
The actual tests -- electroencephalogram (EEG) and electromyogram (EMG) -- help physicians understand the nervous system. An EEG records the electrical waves of the brain. It is a safe, easy and painless test that takes approximately one hour. An EMG evaluates nerve and muscle function in the arms or legs (that may reflect what is happening in the brain, neck or back) and is usually done in conjunction with a Nerve Conduction Velocity test (NCV). It can be a mildly uncomfortable test for some patients, and duration varies based on the number of limbs being tested.
An EEG is used in the evaluation of various suspected brain disorders; seizures, stroke, transient schemic attack (TIA or "min-stroke"), and syncope (fainting) are some of the most common reasons to have an EEG. The testing is performed by a technologist, and involves pasting electrodes to the surface of the head that will record the brain waves at rest and during certain activities. Initially patients close their eyes, but during the test the technologist may routinely ask them to open and close their eyes, hyperventilate, and/or watch a flashing light to see how the brain responds (for example, watching a flashing light can induce seizures in susceptible people). At the conclusion of the test, the technologist removes the electrodes and cleans any remaining paste. There are no restrictions following an EEG. A neurologist specially trained in reading EEGs will interpret the test and send a report of the findings to the referring physician.
EMG and NCV testing are used in the evaluation of carpal tunnel syndrome, peripheral neuropathy (that may, for example, be part of diabetes), and radiculopathy (pinched nerves in the spine), as well as other nerve-related problems. A physician performs an EMG by inserting sterile pins with a microscopic electrode on the tip into certain muscles of the patient's limbs or back. The test can be helpful in evaluating the causes of numbness, tingling, pain, weakness, fatigue and muscle cramping. The NCV test is performed by placing several electrodes on the appropriate limb and applying a mild electric stimulus to the site. This measures the speed of the electrical impulses and provides general information about the health of the nerves being tested and may identify the location of suspected pinched nerves. After the test, the physician will usually briefly explain the findings. The patient may experience a mild discomfort in certain areas of their limbs, but this generally returns to normal within 30 minutes. There are no restrictions or limitations following EMG or NCV testing.
EEG and EMG, while not routinely ordered, are safe and reliable means of evaluating various neurological conditions. If you have questions regarding testing, discuss it with your physician, but you may also feel free to call and speak with the technologist at the neurodiagnostic laboratory performing the test. Also, most hospitals feature educational information on their websites to answer any anticipatory questions.
This article was published as part of the Daily Local News Medical Column series which appears every Monday. It has been reprinted by permission of the Daily Local News.
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