HYPSARRHYTHMIA - FREQUENCY OF VARIANT PATTERNS AND CORRELATION WITH ETIOLOGY AND OUTCOME

To determine the frequency and significance of the EEG features of hyp sarrhythmia, we analyzed the pre-ACTH records of 53 consecutive patien ts with infantile spasms for the severity of the following abnormaliti es: disorganization of background, slowing, high amplitude, spike acti vity, and for the presence or absence of each of the following pattern s and variants: electrodecremental discharges, absence of normal sleep activity, relative normalization, hemihypsarrhythmia, burst suppressi on (BS), occipital hypsarrhythmia, interhemispheric asymmetry, and int erhemispheric synchronization. We calculated a total score indicating the severity of the hypsarrhythmia for each record. The hypsarrhythmia variant patterns occurred frequently in up to 69% of the records. Pat ients with cerebral dysgenesis were more likely to have hemihypsarrhyt hmia or BS pattern persistent throughout the EEG. Patients with histor y of perinatal hypoxia-ischemia were more Likely to have absence of no rmal sleep activity. The occurrence of each of the other variant patte rns did not correlate with etiology. Favorable outcome did not correla te with the occurrence, or absence, of any of the variant patterns but was associated with faster background activity (<75% delta), a lower total hypsarrhythmia score (less than or equal to 10), and with absenc e of electrodecremental discharges on the pre-ACTH EEG. We conclude th at variant patterns of hypsarrhythmia are frequent, generally do not c orrelate with prognosis, and thus are best included within the definit ion of hypsarrhythmia. The severity of the hypsarrhythmia, however, do es have significant prognostic implications.