Abstracts

Rationale: The diagnoses of childhood epilepsy syndromes (CES) are established on clinical characteristics and EEG features (ILEA, 1995). Regardless of the initial syndrome diagnosed, patients may exhibit overlapping CES EEG features with both focal and generalized epileptiform discharges. The clinical implications of coexisting EEG findings are unknown. Here, we reviewed the clinical features of children presenting with both generalized and focal EEG findings. Methods: Ninety-five children were identified for review from the pediatric neurology-epilepsy database (year 2004-2006). In this cohort, benign focal epilepsy of childhood (BFEC) was diagnosed in 32 (33%); childhood absence epilepsy (CAE) in 45 (46.4%); and juvenile myoclonic epilepsy (JME) in 11 (11.3%). Diagnosis of a definitive CES was undetermined in 7 (7.4%). All EEGs were reviewed. Overlapping EEG findings with coexisting features of CAE and BFEC were identified in 24 (24.7%). Demographics, clinical features, school performance and EEG findings of each epilepsy syndrome were reviewed and compared. Statistical analysis was performed using the Student t test and Fischer's Exact test, with level of significance of 0.05. Results: In the cohort with overlapping EEG findings (n:24), the mean age and age of seizure onset was 9.4±4 yrs and 4.6±3.3 yrs (M/F:7/15). EEG findings for all patients included generalized spikes and/or polyspike discharges (3-4 Hz) and independent focal spikes, from either the centro-temporal or occipital regions during non-REM sleep. Focal discharges were first noted at a mean age of 6.8±3.4 yrs. Of 24 patients, initial CES was CAE in 10; BFEC in 7; myoclonic-astatic epilepsy in 1; undetermined in 6. In the undetermined group, 2 presented with only febrile seizures (FS) and 4 with a single afebrile seizure. Six children initially classified as generalized epilepsy (1 with MAE, 5 with CAE) later received the diagnosis of BFEC due to the emergence of focal EEG findings and focal seizures. In contrast, 2 children with BFEC were later diagnosed with CAE during their course. Brain MRI was normal in 24 (100%). FS was reported in 7 (29.2 %) of which febrile status epilepticus was seen in 3. A history of learning disability and developmental delay (fine motor coordination and/or speech delay) and a family history of seizure(s), was more prevalent in this group (p<0.05). Seizure freedom was reported less often (34.6%) compared to the cohort of CES without overlapping features (p<0.05). Conclusions: Coexisting EEG features of CAE and BFEC are not uncommon (24% of CES). Overlapping EEG findings appear to be associated with developmental delay, learning disability, febrile seizures and a family history of seizures. Further study is needed to determine whether this is a consequence of a genetic predisposition affecting both clinical features and EEG findings, or is due instead to a decreased likelihood of seizure freedom as compared to other CES, resulting in a direct impairment on neuropsychological development.