The electroencephalogram in clinical pediatrics

The electroencephalogram represents an electrical summary of the organizational patterns and the total physical-chemical processes taking place in the brain at the time of the recording. Itis affected by (1) artifacts secondary to head movements, muscle potentials, and eye movements, (2) physiological factors, such as state of consciousness, hyperventilation, and maturity of the brain, (3) metabolic factors such as temperature, thyroid function, electrolyte changes, and numerous other metabolic factors, and (4) drugs. Brain dysfunction also causes changes in the electroencephalogram. The electroencephalogram is useful in some, but not all, types of brain dysfunction. In general, the electroencephalogram is most likely to be abnormal if the underlying disease is acute or ongoing, or if the disease is associated with seizures. Focal lesions may appear when none is suspected clinically. The electroencephalogram can be an invaluable aid in dealing with epilepsy. Petit mal epilepsy cannot be diagnosed without it, and infantile spasms are diagnosed with considerably greater certainty if the electroencephalogram shows hypsarrhythmia. Patients with seizures which appear to be generalized may have an electroencephalogram with focal abnormalities; this may be the only clue that a focal lesion exists. Psychomotor epilepsy is sometimes difficult to differentiate from sociopathic behavior, and the electroencephalogram can be helpful. The electroencephalogram is less useful in chronic static conditions such as mental retardation, minimal cerebral dysfunction, or behavior disorders, unless there is associated epilepsy or ongoing brain pathology. More recently, the electroencephalogram has been used to estimate gestational age with reasonable accuracy. With the aid of a computer, responses to auditory and visual stimuli have been recorded on the electroencephalogram. These techniques, although not in general use at the present time, hold considerable promise for the future. They mark the beginnings of a new dimension in using the electroencephalogram as a tool in helping the clinician evaluate and understand brain development, and in helping him recognize early signs of disease in the developing brain.