Abstracts

Rationale: Frontal intermittent rhythmic delta activity (FIRDA) is a transient EEG finding with unknown pathophysiological significance that has been reported in different pathological states involving the central nervous system.FIRDA was initially described in 1945 by Cobbs who attributed the EEG activity to a midline deep lesion but other reports correlate it also to metabolic encephalopathy and structural pathology.FIRDA is known to occur in children as well however there are few studies on the clinical significance of FIRDA and the specific pathologies in the pediatric population.The aim of this study was to determine the correlation between FIRDA and the clinical and radiological studies in children Methods: EEG records from January 1999 to December 2006 from the computerized pediatric EEG data base at the Hospital for Sick Children in Toronto were searched for the abbreviation of FIRDA.All records with reported FIRDA were reviewed by two electrophysiologists that were blinded to any patient data except age and gender.Patients included were between 1-18 years old with a full clinical file follow-up and neuroimaging all done in HSC.Patients were excluded if they were sedated before or during the EEG admitted due to drug intoxication status epilepticus or had electrographic or clinical seizures during the recordings.In addition, hospital and outpatient records were reviewed.Demographic data collected included, gender, age perinatal and postnatal history any possible previous central nervous system insult metabolic or genetic syndromes full neurodevelopmental assessment and current physical status.A complete history of the patient’s epilepsy was documented and any epilepsy syndromes were recorded.The presence of acute illness before or on admission was noted and laboratory data if done were reviewed Results: Out of 14,000 EEG recordings preformed between 1999 and 2006 FIRDA was reported in only 45 children.The EEG recordings of these 45 children were independently reviewed by two neurophysiologists and 37 cases with FIRDA were identified.Of the 37 cases 20 were female and 17 male.The duration of FIRDA was from 3-4 seconds in 7 children 5-8 seconds in 10 children up to 9-11 seconds in 20 children.In 74% of children at least one abnormal neurological exam prior its documentation and patients with abnormal neurological exam had a longer FIRDA duration compared to children than did no have abnormal reported examination.The oscillation frequency of FIRDA varied from 2 to 2.5 Hz in 15 cases, 3 Hz in 17 cases and from 1.5 to 3 Hz in 5 cases. There was a significant association between the duration of FIRDA and the abnormal laboratory findings (t = (1, 27), p<.02) Conclusions: To date our report involves the largest group of children with FIRDA.Origin of FIRDA in children remains unclear and un frequent(0.26%).Although FIRDA was frequently associated with epileptiform discharges on EEG the discharges were infrequently localized to the frontal region.FIRDA was not correlated with midline brain lesions in children and it may be a non specific oscillation of an unhealthy pediatric brain with or without seizures.