One-third of patients with epilepsy who undergo continuous EEG monitoring exhibit periodic discharges or rhythmic activity that lie on a spectrum known as the ictal‒interictal continuum.3 Depending on the type of these discharges there is a certain risk of seizures and also mortality.3 While lateralized periodic discharges are associated with the highest risk of seizures, bilateral independent periodic discharges are associated with the greatest risk of mortality.3
References:
1. Pressler RM, Cilio MR, Mizrahi EM, et al. The ILAE classification of seizures and epilepsies: modification for seizures in the neonate. Position paper by the ILAE Task Force on Neonatal Seizures. Epilepsia 2021; 62 (3): 615‒628.
2. Stead M, Bower M, Brinkmann BH, et al. Microseizures and the spatiotemporal scales of human partial epilepsy. Brain 2010; 133 (9): 2789‒2797.
3. Johnson EL, Kaplan PW. Population of the inter-ictal zone: The significance of periodic and rhythmic activity. Clin Neurophysiol Pract 2017; 2: 107‒118.
4. Vossler DG. First seizures, acute repetitive seizures, and status epilepticus. Continuum (Minneap Minn) 2025; 31 (1): 95‒124.