Noran Neurological Clinic
EEG/EMG EEG/EMG

Electroneurodiagnostics

Electroneurodiagnostic (END) technology is the study and recording of electrical activity of the brain and nervous system. Technologists record electrical activity arising from the brain, spinal cord, peripheral nerves, somatosensory or motor nerve systems using a variety of techniques and instruments. A neurologist interprets the test results and reports these findings to referring physicians as necessary.

Common electroneurodiagnostic procedures include the electroencephalogram (EEG), long-term monitoring, evoked potential studies, and nerve conduction studies.

Electroencephalogram (EEG)
The EEG is a recording of the on-going electrical activity of the brain. An EEG can assist in the diagnosis of a variety of neurological problems-from common headaches and dizziness to seizure disorders, strokes and degenerative brain disease. The EEG is also used to determine organic causes of psychiatric symptoms and disabilities in children.

Sleep-Deprived EEG
This test is similar to a regular EEG, as described above, except that you will be asked to stay awake for 24 hours prior to your exam time. Children under the age of 12 who take this test are asked to remain awake from midnight until exam time.

Ambulatory EEG
This test is similar to a regular EEG, as described above, except that the monitoring takes place over an extended period of time and in the comfort of your home.

Overnight Video EEG / Long Term Monitoring (LTM)
An overnight video EEG is a prolonged EEG study accompanied by continuous video monitoring, which can record both the clinical events and EEG recording to aid in the diagnosis of seizures and other neurological disorders. You will have electrodes placed with a water-soluble paste and be monitored during the afternoon and into the evening.

Carotid Ultrasound and Doppler Tests
These tests use high-frequency sound waves and a computer to show and analyze the blood flow to the carotid artery. Each test takes about 15 minutes and no preparation is necessary on your part.

Evoked Potentials (EP)
The Evoked Potential is a recording of electrical activity from the brain, spinal nerves, or sensory receptors that occurs in direct response to external stimuli. EP waveforms require sophisticated computer equipment to extract data that will allow physicians to determine the functional state of these pathways. This test is commonly performed by the technologist during surgery on the spine to help the surgeon make sure nerves are not damaged during the operation. Evoked Potentials are also performed in a clinical END laboratory, using either earphones to stimulate the hearing pathway, a checkerboard pattern on a TV screen to stimulate the visual pathway, or a small electrical current to stimulate a nerve in the arm or leg.


Electromyography (EMG) & Nerve Conduction Studies

What are they? 

Electromyography (EMG) and nerve conduction studies (NCS) are two tests used to help diagnose nerve and muscle disorders.  Although they are sometimes ordered independent of each other, they are often ordered together to be done in the same appointment.  You can normally expect to complete both during your appointment.
• EMG measures electrical impulses in the muscles.
• Nerve conduction studies measure the speed and intensity of electrical signals that travel along the nerves, and the time it takes muscles to respond to these signals.

When are these tests helpful?

They are often used when a patient has symptoms such as muscle weakness, numbness, spasms, paralysis or pain.

A nerve conduction study is used to help evaluate or diagnose:
• Carpal tunnel syndrome and other mononeuropathies of the extremities
• Focal numbness and weakness
• Peripheral polyneuropathies
• Generalized weakness
• Myasthenia gravis

An EMG is used to help evaluate or diagnose:
• Muscle diseases
• Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
• Nerve compression in the neck, back or extremities
• Peripheral polyneuropathies
• Disorders of neuromuscular transmission
• Cervical and lumbar radiculopathies
• Generalized weakness
• Focal weakness

Why are these tests helpful?

Nerves send electrical signals to muscles, cueing them to contract or relax, and muscles produce electrical activity when they move. When injury or disease affects nerves or muscles, the electrical activity changes. Electromyography and nerve conduction studies show those changes and help your physician make a diagnosis and determine treatment options.

How is a nerve conduction study conducted?

In nerve conduction studies, stimulating electrodes are held against your skin. No needles are used. A tiny impulse is sent through your nerves and the responses are recorded.  This test may be done by either our experienced EMG technician or the same doctor who will conduct the EMG.

This current is harmless and lasts 0.1 to 0.2 milliseconds. You may feel a tingling or your muscles, fingers or toes might twitch.

Usually the test takes about an hour and is done on an outpatient basis. You can resume normal activities once the nerve conduction study is completed.

How is an EMG conducted?

In EMG, the health care provider gently inserts a thin needle electrode into each muscle to be studied. You may feel a brief pain as the electrode is inserted, but because of its small size and because nothing is inserted through the electrode, the pain is less than a typical hypodermic injection. Most people tolerate the minor discomfort quite well.

A fine wire connects the electrodes to an electronic instrument that measures electric currents in the muscle. You’ll be asked to slowly flex muscles so the electrical activity can be measured.

Usually, the test takes about a half hour and is done on an outpatient basis. You can resume normal activities once the EMG is completed.

Who conducts these tests?

A board-certified neurologist typically conducts these tests and interprets the results. Some neurologists are board certified in electromyography, indicating advanced training in the field.  In some appointments, a qualified EMG technician will conduct the first nerve conduction study portion of the testing, while a neurologist will always conduct the EMG.

The specialized neurologist also interprets the results, which requires analysis of the data transmitted to the computer and listening to the electrical impulses during the tests. Results are forwarded to your physician.

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