Periodic electroencephalographic (EEG) patterns are fre-quently recorded during ICU EEG monitoring in patients with Altered Mental Status; these EEG features represent electrical discharges, ictal in appearance, occuring at regular intervals. They are known as Lateralized Periodic Discharges (LPDs), Bilateral Independent Periodic Discharges (BIPDS), Generalized Periodic Discharges (GPDs), Continuous 2/s GPDs with Triphasic Morphology or Triphasic Waves (TWs) ,and Stimulus Induced Evolving Lateralized Rhytmic Delta Activity or Si-Evolving LRDA (previously SIRPIDS); other periodic, rhythmic patterns are Occasional frontally predominant brief 2/s GRDA (FIRDA previously), Lateralized rhythmic delta activity (LRDA) and Brief potentially ictal rhythmic discharges or B (I)RDs. The role of most (not all) of these EEG patterns is contro-versial; there is no consensus on which patterns are associ-ated with ongoing seizure injury, which patterns need to be treated, and how aggressively they should be treated. Many authors consider these patterns as an unstable state on an ic-tal-interictal EEG continuum; the aim of this presentation is to gain knowledge of these EEG features, show their asso-ciation with known neurologic pathologies/syndromes and the best way 

to manage them.