Clinical Associations of Occipital Intermittent Rhythmic Delta Activity

Abstract

Association of occipital intermittent rhythmic delta activity with absence seizures has been well documented in the published literature. Two recent studies have also described an association with focal seizures. After obtaining approval from our Institutional Review Board, all electroencephalograms with occipital intermittent rhythmic delta activity at our institution between July 1, 2006 and December 31, 2009 were identified. Charts of these patients were reviewed to collect clinical data. A matched comparison group was assembled. Thirty-one of the patients who met criteria had evaluable clinical data. Fifteen had generalized seizures (9 absence; 2 tonic-clonic; 3 absence and tonic-clonic; 1 absence, tonic-clonic, myoclonic, and atonic). Eleven had focal seizures. One had both generalized tonic-clonic and focal seizures. Events in 1 were nonepileptic in nature. Documentation was inadequate for seizure classification in 3. There was a statistically significant difference between the study and comparison groups for absence seizures, but not for focal seizures.

Occipital intermittent rhythmical delta activity in a schoolgirl with microcephaly

“…Gullapalli and Fountain [6] found that the most frequent convulsive episodes in patients with OIRDA are generalized tonic-clonic and absence episodes. Thirty percent of epileptic discharges occur in epileptic patients as compared to 12.5% in patients without convulsive episodes [6,12]. Occipital intermittent delta activity in most patients occurs during wakefulness and hyperventilation [8], as in our case.…”

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

“…[3] In another study, Desai et al studied 31 cases and found that absence seizures were more frequently seen in patients with OIRDA. [8] In our patient, the main clinical picture consisted of periods of frequent and serious visual hallucinations and severe headache. Visual hallucinations may be major symptoms of occipital lobe epilepy as well as migraine aura.…”

Occipital intermittent rhythmic delta activity (OIRDA) in pediatric focal epilepsies: A case series

“…In accordance with the American Clinical Neurophysiology Society’s standardized critical care EEG terminology (2021 version), Rhythmic Delta Activity (RDA) is defined as a waveform with relatively uniform morphology and duration, without an interval between consecutive waveforms, and a frequency of 0.5 to ≤4.0 Hz [15] . Although OIRDA has been documented previously in cases of focal epilepsies [14] in addition to CAE, repeat studies have not corroborated this as a statistically significant correlation [13] . Our case series, albeit limited in number, illustrates the presence of OIRDA in children with focal epilepsies and some atypical features as compared to that published in cases of CAE.…”

“…OIRDA appears to be a relatively rare finding, with rates being reported between 0.75% [13] to 3.4% [14] of studies showing this finding. Given the relative rarity of OIRDA, and potential pathophysiological implication, further studies are necessary to determine if a correlation exists between OIRDA spatial distribution and localization, epileptiform features, cortical versus subcortical origin, or if this proposed link between CECTS/PS, and OIRDA represents a temporal progression or resides on a spectrum of focal and generalized abnormalities when OIRDA is seen in these patients.…”

“…We identified OIRDA in three pediatric patients with focal epilepsies, including Self-limited Childhood Epilepsy with Centrotemporal Spikes (CECTS) [11] , [12] , and Benign Childhood Epilepsy with Occipital Spikes, formerly known as Panayiotopoulos syndrome (PS). We have identified some ‘atypical’ or focal features of OIRDA in patients with focal epilepsies, including lateralized OIRDA, a notched morphology or embedded sharp wave forms ipsilateral to focal centrotemporal or occipital spikes, and lack of prominent field of distribution, implicating a focal origin, and perhaps a link between this ‘atypical’ OIRDA and a spectrum of idiopathic focal epilepsy syndromes [13] , [14] .…”