Brief Potentially Ictal Rhythmic Discharges [B(I)RDs] in Non-critically Ill Adults.

INTRODUCTION: Brief potentially ictal rhythmic discharges (B(I)RDs) have been described in neonates and critically ill adults, and their association with seizures has been demonstrated. Their significance in non-critically ill adults remains unclear. We aimed to investigate their prevalence, electrographic characteristics and clinical significance.

METHODS: We identified adult patients with B(I)RDs who received long term EEG recordings either in the epilepsy monitoring unit or in the ambulatory setting. Patients with acute findings on imaging or status epilepticus were excluded. B(I)RDs were defined as very brief (<10 seconds) runs of focal or generalized sharply contoured rhythmic activity greater than 4 Hz, with or without evolution, that were not consistent with any known normal or benign pattern. The clinical history, EEG and imaging results were retrieved. Each patient with B(I)RDs was matched by age and etiology to a control group with epileptiform discharges but without B(I)RDs in a 1:2 ratio.

RESULTS: We identified B(I)RDs in 15 patients out of 1230 EEGs (1.2%). The pattern typically consisted of 0.5-4 second runs of sharply contoured alpha activity without evolution. All patients with B(I)RDs had epilepsy, and, when compared to controls with epilepsy but without BIRDs, were more likely to be medically refractory (10 of 15 [67%] vs. 5 of 30 [17%]; p<0.01). All seizure onsets co-localized to the B(I)RDs, and most were morphologically similar.

CONCLUSIONS: In non-critically ill patients, B(I)RDs are associated with refractory epilepsy and their location is correlated with the seizure onset area.