Which rhythm is considered abnormal in an EEG for a child below one year of age?

The rhythm of 1 to 2 Hz is considered abnormal for a child below one year of age. In this age group, a normal electroencephalogram (EEG) typically displays higher frequency rhythms, such as slower delta waves or faster theta and alpha waves as the child develops, especially as they approach their first birthday.

For infants, the dominant brain rhythms generally start from drowsy or sleep states characterized by mixed frequency activity, including sleep spindles and theta activity, which emerge progressively. A rhythmic pattern of 1 to 2 Hz indicates very slow brain activity, which is not typical for infants and could suggest significant neurological issues, such as encephalopathy or seizure activity.

Other options refer to rhythms that are generally seen as more typical within the EEG patterns of infants. Frequencies such as 5 to 6 Hz, 8 to 10 Hz, and 3 to 4 Hz can be observed in developing children’s EEGs and could appear during awake states or in certain sleep stages, where rhythmic activity is more common. Thus, the frequency of 1 to 2 Hz stands out as the abnormal pattern in this context.