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Three special procedures that may be part of the routine EEG— sleep-induction, hyperventilation, and photic stimulation—are called “activation” procedures because they can “activate” patterns of abnormalities on the EEG. Such procedures should be routine with children.”Why do they do the test both awake and asleep?”The EEG looks quite different, depending on whether the patient is awake or asleep. Some abnormalities, spikes for example, may be apparent only in a drowsy or sleep state because sleep changes the organization of brain waves and may allow hidden abnormalities to show up. Some children with epilepsy may have a normal EEG awake and a very abnormal EEG when asleep.”What is hyperventilation, and why is It done?”The technician will ask your child to breathe deeply, thus causing changes in the blood carbon dioxide and usually resulting in slowing on the EEG. Such changes as a consequence of hyperventilating are far more pronounced in younger children than in older ones. They can reveal abnormalities on the EEG. In children with absence seizures, overbreathing can even cause a clinical spell and allow the EEG characteristics of this form of epilepsy to become overt.”What Is photic stimulation?”Flashing lights also may trigger seizures. A special class of seizures is called “photic sensitive seizures.” Using a stroboscopic light, which flashes at frequencies from one per second to sixty per second, the EEG technician can observe whether the child is “photic sensitive,” that is, that the child’s EEG responds to certain frequencies of flashes, with the EEG showing spikes every time the light flashes. Occasionally, “photic driving” can make the brain so active that a real seizure will occur, one similar to episodes that occur under nonlaboratory conditions in a few people, who are then said to have “photic sensitive epilepsy.”*83\208\8*

“Circe’s teacher called us this week because she is daydreaming in class. We had told her to watch for seizures in the beginning of the year, and now she thinks that Circe is having absence seizures again. Should we increase her medicine?”
Circe could be having more absence seizures. Perhaps this alert teacher has identified the problem early. Have you seen any at home? Is Circe aware of missing things? Is it possible that the teacher is just watching too closely and misinterpreting things? Perhaps we should first check the blood level to be certain that she is taking the medication and taking enough. Perhaps we should see Circe and hyperventilate her to see if we can produce one of her spells. If we can’t be sure in the office, we might want to have another EEG to see if she is still having electrical spells. In this way we can sort out if Circe has a problem and the best approach to correcting it.
Learning problems are more common in children who have epilepsy. Early identification of a problem, if it exists, can lead to strategies for compensation and a far more successful school learning experience. However, learning problems can also be secondary to the medication, to psychological stress, and to the school’s and the teacher’s reaction to the child and to epilepsy. Changes in school performance are best identified by the teacher, who, together with your physician, can also be your and your child’s best ally in finding the cause and the best approach to a solution.
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