Clinical Correlates of Occipital Intermittent Rhythmic Delta Activity (OIRDA) in Children

Abstract

Summary: Purpose:The clinical significance of occipital intermittent rhythmic delta activity (OIRDA) on the electroencephalogram has not been fully established. Recent studies suggest that this pattern occurs almost exclusively in children and is probably of epileptic origin in most cases. We sought to characterize the electrographic features and clinical correlates of occipital intermittent rhythmic delta activity.Methods: A review of 697 consecutive pediatric electroencephalograms detected occipital intermittent rhythmic delta activity in 24 studies. Mean patient age was 7.96 years.Results: Recent convulsions and absence seizures constituted the main indications for the study. Concomitant, independent epileptiform activity was noted in half of the cases. This activity was focal in all but one case. Conversely, in most cases of absence seizures, epileptiform activity intermixed with occipital intermittent rhythmic delta activity. Furthermore, the frequency of the occipital rhythmic discharges in studies of children with absences was generally faster (3-4 Hz) than in localizationrelated epilepsy (2-3 Hz). Most patients were awake when occipital intermittent rhythmic delta activity occurred. Chronic encephalopathy was seen in one child only. Analysis of neuroimaging studies in eight cases revealed no structural pathology associated with occipital intermittent rhythmic delta activity.Conclusions: Occipital intermittent rhythmic delta activity is probably an epileptiform pattern, although it is noted occasionally in encephalopathic children. Its electrographic characteristics appear to differ between localization-related epilepsy and primary generalized epilepsy, particularly absence seizures.

Non-epileptiform EEG abnormalities: an overview

“…Lesions in the occipital lobe with involvement of the posterior lateral ventricle may lead to the emergence of OIRDA as a projected rhythm 13 . However, OIRDA seems related to the presence of epilepsy, especially generalized, in children 7,9 . Generalized absence seizures and tonic-clonic seizures are more frequent in children with OIRDA, and its presence in children with typical absence seems to be a good prognostic factor 7 .…”

“…Generalized absence seizures and tonic-clonic seizures are more frequent in children with OIRDA, and its presence in children with typical absence seems to be a good prognostic factor 7 . In 15 to 30% of children with absence epilepsy, the interictal EEG may also contain OIRDA at 3.0 to 4.0 Hz, which has a high amplitude, without sharp waves 9 . Dysfunctions probably located in the brainstem and diencephalon, or in their non specific projections, would explain the coexistence of spike and wave activity and OIRDA in children with typical absence seizures 7 .…”

“…Dysfunctions probably located in the brainstem and diencephalon, or in their non specific projections, would explain the coexistence of spike and wave activity and OIRDA in children with typical absence seizures 7 . When the EEG shows unilateral FIRDA or OIRDA, it generally indicates a focal than diffuse disturbance, and sometimes its occurrence is contralateral to the pathology 9,23,24 . When it is due to a focal lesion and presented as bilateral and symmetric, this lesion classically is near the third ventricle, diencephalic or mesencephalic midline, brainsteim or cerebellum 15,26 .…”

“…The EEG provides valuable information on the investigation of patients with signs of acute cerebral suffering, rapidly progressive dementia, toxicmetabolic encephalopathy, coma and brain death, among others [2][3][4] . It is worth remembering that the non-epileptiform EEG abnormalities may be present in patients with epilepsy [5][6][7][8][9] . Vanrumste et al 5 demonstrated the presence of non-epileptiform activity arising from the same area as epileptiform activity in five children with focal epilepsy, using an automated technique.…”

Occipital Intermittent Rhythmic Delta Activity (OIRDA) and Occipital Seizures in an Elderly Patient

“…In a limited number of studies that included childhood cases in recent years, it is suggested that OIRDA is an interictal EEG finding, which is mostly specific to children. [2,3,7] Another EEG finding localized to posterior regions is Pi rhythm which was used by Silbert et al to identify a form of occipital slow waves which does not have any significance regarding epilepsy. Pi rhythm is a series of short, monomorphic occipital slow waves that is seen only in children and adolescents and occur in the first 2 seconds following eye closure.…”