Norm of Electroencephalography (EEG)
Normal electrical brain activity as recorded by the EEG instrument.
Usage of Electroencephalography (EEG)
Used as a diagnostic tool in the diagnosis of Alzheimer's disease (declining D alpha values), attention-deficit/hyperactivity disorder (ADHD), different central nervous system disorders including tumors, infections, and various encephalopathic states. Special use involves the characterization of various types of seizure disorders and also the determination of the anatomic locus of seizure activity within the brain (the “seizure focus”). The EEG is also of value in the determination of central nervous system death (“brain death”). It is occasionally helpful in establishing the diagnosis of various neurosensory disorders when used in its applied forms (the recording of “visual evoked” and “auditory evoked potentials”).
Description of Electroencephalography (EEG)
Using a special cap, electroconductive gel, and electrodes, an EEG recording of the electrical potentials of the cerebral cortex of the brain is taken and subsequently analyzed to determine the presence or absence of various waveform activities.
Professional Considerations of Electroencephalography (EEG)
Consent form NOT required.
- See Client and Family Teaching.
- Although portable EEG equipment is available, the test is generally conducted in an EEG lab by a neurologist or an EEG technician.
- Sedative drugs and prolonged fasting (hypoglycemia) can influence the test and should be avoided if possible.
- The client is placed in a recumbent position in a darkened room.
- A cap with numerous plastic electrode locators is placed on the client's head, and the openings in the electrode locators are filled with electroconductive gel.
- Electrodes are inserted through the locators into proximity with the client's scalp. (It is not necessary to shave or puncture the scalp to accomplish this step.)
- EEG recordings are made in the supine position. The client may be asked to perform various physical maneuvers during the test; occasionally recordings are made during sleep.
- Electrodes and EEG cap are removed and the gel is wiped from the scalp.
Client and Family Teaching
- Pretest orientation with a description of the method used to attach the electrodes is important.
- Shaving of the scalp hair is not necessary for this test.
- Hair should be free of products such as gel or hair spray, which could interfere with conductivity to the electrodes.
- It is important to lie still throughout the test.
- If the EEG is used as an adjunct in the determination of brain death, a detailed description of the test and the rationale behind its use in this setting should be given to the family.
- The procedure may take up to 2 hours.
Factors That Affect Results
- Hypoglycemia (prolonged fasting) may decrease response time, leading to an abnormal pattern.
- Certain sedative drugs can affect the EEG pattern.
- Caffeine causes significant reduction of total EEG power at frontoparieto-occipital central electrode positions of both hemispheres when subjects have their eyes open.
- Oily hair or hair spray interferes with the recording because it reduces conductivity to the electrodes.
- Sleep, motor activity on the part of the client, muscle tension, and various external sensory stimuli may interfere with the waveform patterns and prolong the test.
- Prolonged (semiambulatory) EEG recordings may be valuable in the management of certain clients with epilepsy.
- The EEG may be used as an evaluation tool in the management of anesthesia and sedation.
- A single negative EEG finding should not rule out a seizure disorder. Serial or repeated EEG tracings are necessary.
- See also Visual evoked potentials.