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 noncritically ill adults remains unclear. We aimed to investigate their prevalence, electrographic characteristics, and clinical significance.
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.
We identified B(I)RDs in 15 patients of 1,230 EEGs (1.2%). The pattern typically consisted of 0.5 to 4 second runs of sharply contoured alpha activity without evolution. All patients with B(I)RDs had epilepsy, and, when compared with 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 colocalized to the B(I)RDs, and most were morphologically similar.
In noncritically ill patients, B(I)RDs are associated with refractory epilepsy and their location is correlated with the seizure onset area.
*Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, U.S.A.;
†Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, U.S.A.; and
‡Department of Neurology, Université Libre de Bruxelles, Brussels, Belgium.
Address correspondence and reprint requests to Ji Yeoun Yoo, MD, Epilepsy Center, Department of Neurology, Mount Sinai Hospital, One Gustave L. Levy Place, 2nd floor/Box 1052, New York, NY 10029, U.S.A.; e-mail: email@example.com.
JY Yoo, L. V. Marcuse, and M. C. Fields receive royalties from Elsevier for coauthoring the book, “Rowan's primer of EEG”. N. Gaspard receives: Consultancy fees from Sage Therapeutics, Inc; Research funding through the Belgian Fund for Scientific Research (FRS/FNRS), the Fonds Erasme pour la Recherche Médicale, and the Daniel Raymond Wong Neurological Research Fund. L. J. Hirsch has received: Research support to Yale University for investigator-initiated studies from Upsher-Smith, Lundbeck, Eisai, Sunovion, and Acorda; Consultation fees for advising from Upsher-Smith, Marinus, Monteris, Sunovion, and Ceribell; Royalties for authoring chapters for UpToDate-Neurology, chapters for Medlink-Neurology, and from Wiley for coauthoring the book “Atlas of EEG in Critical Care,” by L. J. Hirsch and Brenner; Honoraria for speaking: Neuropace; L. J. Hirsch spends about 25% of his clinical billable time implementing and interpreting critical care EEG studies. The remaining authors have no funding or conflicts of interest to disclose.
The abstract and poster were presented at the American Clinical Neurophysiology Society annual meeting in Houston, Texas, February 7, 2015.