Abstract
Periodic electroencephalographic (EEG) patterns are frequently 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 controversial; there is no consensus on which patterns are associated 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 ictal-interictal EEG continuum; the aim of the present chapter is to gain knowledge of these EEG features, show their association with known neurologic pathologies/syndromes and finally how to manage them.
Highlights
Periodic electroencephalographic (EEG) patterns are frequently recorded during Intensive Care Unit (ICU) EEG monitoring in patients with Altered Mental Status (AMS) [1]; these controversial EEG patterns consist of discharges usually epileptiform in appearance, which occur at regular intervals, in critically ill patients
lateralized periodic discharges (LPDs) are stereotyped, repetitive EEG discharges and recurr periodically at regular intervals at 0.5 to 3 Hz; they are broadly lateralized over one hemisphere, over the parasagittal and temporal areas; LPDs are usually epileptiform in appearance; they appear like sharp waves/sharp waves complexes ranging from 50 to 300 uV in amplitude or as blunt delta waves that recur in stereotyped periodic fashion (Figure 1)
Stimulus induced evolving lateralized rhytmic delta activity (Si-evolving Lateralized rhythmic delta activity (LRDA)). These EEG features were recently described by Hirsch et al in ICU patients [8]. They occur whenever ICU patients with AMS are stimulated using auditory, sternal rub, suctioning, or other stimulating procedures (Figure 13); these curious EEG patterns appear ictal, they are sometimes associated with an evolving lateralized rhythmic delta activity, stimulus induced ; Si-Evolving LRDA looks like an epileptiform activity recurring at regular intervals; there are in general purely EEG changes; few patients showing these features present focal motor seizures
Summary
Periodic electroencephalographic (EEG) patterns are frequently recorded during ICU EEG monitoring in patients with Altered Mental Status (AMS) [1]; these controversial EEG patterns consist of discharges usually epileptiform in appearance, which occur at regular intervals, in critically ill patients. They are commonly classified as periodic lateralized discharges (PLDs), bilateral independent PLDs or BIPLDs, generalized periodic discharges (GPDs) and triphasic waves. The aim of this study is to make a review of these periodic EEG features, emphasizing the importance of their recognition and clinical significance Their clinical significance is uncertain, it is related to a variety of etiologies, and many authors suggest that these patterns are unequivocally epileptogenic in some cases. Their recognition and classification are important to establish a correlation between clinical, neurological, neuroimaging data with the EEG results
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