Abstracts

Rationale: The cyclic seizure (CS) pattern was initially reported in patients with critical illness. This CS EEG pattern is difficult to appreciate on standard EEG recordings and CS are best detected using digital trending analysis (DTA) applied to standard EEG. In this study, we examined the incidence, clinical and EEG features of CS in children with Status Epilepticus (SE). Methods: The EEG reports of all children (0-18 years) diagnosed with SE were reviewed (2002-2010). Children with repetitive seizures (>2 seizures on the same EEG recording) were identified based on the EEG report, the EEG files were retrieved for review, and DTA applied to further assess the EEG features of CS. Subsequently, clinical and EEG features of children with SE and CS were reviewed and compared to children without CS. Results: A total of 279 children were identified with the diagnosis of SE in which febrile SE (FSE) occurred in 106 (38%), non-convulsive SE (NCSE) in 12 (4.3%) and newborn SE in 6 (2.2%) patients. Refractory status epilepticus (RSE) occurred in 21 (7.5%). EEG recording was obtained in 173 (62%). The diagnosis of epilepsy was present in 78 (28%). Repetitive EEG seizures were identified in 34 children; 28 (82%) of these had CS subsequently identified. The mean age was older in CS group (5.4 5.1) compared to non-CS group (3.8 3.8) (p: 0.047). In CS group, twelve (43%) were previously healthy, 16 (57%) had developmental delay,16 (57%) had epilepsy and 9 (32%) had with RSE. Only two children with FSE had CS. The entire duration of the CS pattern ranged from 20 min to 10 hr, individual seizure duration from 30 seconds (sec) to 180 sec, and inter-seizure interval from 40 sec to 300 sec. Except for one, focal seizures occurred in all with CS. Non-convulsive seizures (NCS) were identified in 13 (46%), and NCSE in 5 (18%). Developmental delay (57% vs 36%, p: 0.034), a history of epilepsy (57 vs 28%, p: 0.07), and RSE (33% vs 7.5%, p<0.001) were seen more often in CS group. CS was rarely reported in association with FSE (p: 0.001). SE presenting with focal clinical features, repetitive clinical seizures, RSE, and history of epilepsy are the strong predictors for cyclic seizures (p<0.05). Age, gender, and developmental delay were not risk factors for CS. Conclusions: CS are not uncommon in children with SE. CS are difficult to recognize using standard EEG recordings and best detecting using DTA. Overall, CS occurs in one out of ten children with SE and in slightly over one half of children with an acute exacerbation of epilepsy. In addition, this CS pattern may predict RSE. Therefore, this unique EEG pattern requires special attention during the treatment of SE and may give insight into the pathophysiology of SE.