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Normal EEG in children
Introduction
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.
Normal Awake
3-12 months
14 months-2years
- 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.
3-4 years
5-10 years
- 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.
11-16 years
- 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.
**Hyperventilation**
- 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.
Discussion