The influence of end-tidal carbon dioxide tension on EEG changes during routine hyperventilation in different age groups

Is hyperventilation an effective ''activating'' procedure in routine clinical EEG studies in children?

Electroencephalography (EEG) records of consecutive 275 children (ages 3-18 years; average 11 years; 34.5% females), with generalized epilepsy, consistent with epileptiform discharges in baseline EEG, who underwent 5 minutes of voluntary hyperventilation during standard EEG recordings were reviewed in this study to determine the actual value of the voluntary hyperventilation in routine clinical EEG in provoking epileptiform EEG abnormalities. Of the 275 EEG records, only in 11.6% hyperventilation revealed increased interictal epileptiform discharges as evidenced by increase in frequency during hyperventilation when compared with the baseline EEG and in 0.7% ictal epileptiform discharges without clinical seizure. None of the 275 children elicited clinical seizure during hyperventilation. The value of voluntary hyperventilation as an ''activating'' procedure in routine clinical EEG studies even in children with generalized epilepsy was questioned in this study.

Correlation of electroencephalogram, respiration and movement in the Rett syndrome

Day time video records of 14 girls with the Rett syndrome (RS) (6-17, mean 7 years) were analysed to correlate episodic abnormalities in respiration, movement and electroencephalograms (EEG). Records were compared with those of 12 healthy girls (6-18, median 14 years) who hyperventilated voluntarily. Three RS girls (6-7 years) had minimal respiratory dysrhythmia and showed no correlation between EEG respiration and movement. The other 11 RS girls (6-17 years) had severe awake respiratory dysrhythmia; 10 showing hyperventilation (with hypocapnia) which alternated with active expiratory apnoeic pauses and one with the latter only. All had periods of awake regular breathing with normal respiratory gases. In these girls EEG showed non-epileptic generalised slow activity some of which was paroxysmal. In the six youngest (6-10 years) of these 11 RS girls, non-epileptic paroxysms of EEG slow activity at 1 1/2-4 Hz occurred and were associated with periods of normal breathing and normal pCO2 levels whether girls were alert, drowsy or asleep, but were uncommon during episodes of hyperventilation (and hypocapnia). In four of these girls the EEG paroxysms occupied less than or equal to 1-3% of the time during periods of respiratory dysrhythmia (81 minutes) and 8-100% of the time during alert periods with normal breathing (29 minutes), p less than or equal to 0.001 for this difference. Short bursts of EEG slowing occasionally followed prolonged apnoeic pauses. In two cases brief partial complex seizures occurred. In five of these girls stereotypic movements exacerbated during episodes of respiratory dysrhythmia and reduced during normal breathing.(ABSTRACT TRUNCATED AT 250 WORDS)