Normal EEG in children

The electroencephalograms (EEGs) of infants and children are normally characterized by a greater mixture of waveforms and frequencies than is found in adults.The relative predominance of these wave types varies with age. There may be considerable intersubject variability, possibly because of differences in maturation. Several waveforms, such as the initial response to hyperventilation and posterior slow rhythms of youth, may be normally asymmetrical. Moreover, infants and young children tend to become drowsy during the recording, and the electrographic alterations with drowsiness are greater than those with adults. These factors create wider limits of normality than might be expected in adults. In addition, the superimposition of two or more waveforms often creates sharply contoured waves that can be mistaken for spikes. Fortunately, most of the clinically significant EEG abnormalities in children are morphologically well defined. However, to identify abnormalities in children's EEGs with confidence, it is first necessary to sharpen one's concept of normal features and their variations.

• Pace of development slows in second year
• Theta and central rhythms better developed
• Delta still prominent. Relative paucity of frontal rhythmsEye closure elicits posterior rhythms at higher frequency than in first year
• Eyes open unless indicated.

• Slow pace of development
• Well-developed alpha with eyes closed
• Variable quantity of posterior theta and delta that may be asymmetrical.
• Variable quantity of diffuse theta.
• Delta persists at about 20 to 30µV, principally with eyes open.
• Prominent central rhythm (mu) that may resemble spikes and may be asymmetrical.

• Well-developed alpha
• Variable quantity of posterior slow waves that may be asymmetrical
• The previous two features in combination create sharply contoured waves that are not spikes
• Diffuse theta has diminished but continues
• Minimal diffuse delta, principally with eyes open.

• Initially accentuates background including posterior slow waves
• Posterior build-up usually precedes anterior build-up
• Asymmetrical bursts normally occur, usually maximum left
• Sharply contoured waves common.

Slight increase in ongoing theta and delta in some patients in first year.Spontaneous eye closure may elicit posterior rhythms in early drowsiness, but slower than when awake. Trains of diffuse rhythmic theta may be maximum centrally, posteriorly, or anteriorly. Principally 3 months to 4 years. Most common pattern. Beta accentuation, diffuse or maximal anteriorly or posteriorly, maximal at 5 to 18 months. Decrease in ongoing activity: delta, beta. Combinations of the previous features may occur in sequence: Certain combinations may occur simultaneously.

Bursts of 2 to 5 Hz sinusoidal waves, usually maximal frontocentrally. Superimposed on other drowsy patterns. Begin at 14 to 18 months; most common at 3 to 5 years; seen until age 11 years.

Of higher voltage and briefer than in adults, therefore spike-like. Variable morphology and polarity. May occur sequentially. Shifting asymmetries. Begin at 3 to 4 months, maximal at 3 to 4 years.

First clearly expressed at 3 to 4 months. More numerous and longer at 3 to 9 months than later. Asynchrony common in first year. Central–parietal location in early childhood. May be comb-shaped.

V waves, spindles, and other central sleep rhythms combine to create sharply contoured waves that are not spikes.

Also known as lambdoid waves. Monophasic. Sharply contoured. Electropositive. Bioccipital. Singly or in 4 to 5 s sequences. Occur in most normal subjects.

Normal component of moderate to deep sleep under 5 years.

Electropositive sharp components repeat at 14 and/or 6 to 7 Hz per second. Positive component apiculate or arciform. Negative component smooth. Occur singly or in bursts. 13 to 17 Hz or 6 to 7 Hz; principally 14 or 6 Hz. Posterior temporal and adjacent areas. Widespread field. Best recorded with coronal or referential montages. Duration: Seen in adolescents and young adults. Occur during drowsiness and sleep.

Initial stimulus evokes one or more broad V waves. Then 4 to 8 Hz diffuse rhythmic waves, maximum frontal-central occasionally mixed with delta. Then 1 to 3 Hz diffuse delta. Posterior delta is independent of anterior delta and persists longer. Then delta merges with 4 to 5 Hz waves.