**6. Stimulus induced evolving lateralized rhytmic delta activity (Si-evolving 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 also; Si-Evolving LRDA looks like an epileptiform activity recurring at regular intervals; there are in general purely EEG changes; however, few patients showing these features present focal motor seizures.

No data are available regarding the pathophysiology and prognostic significance of these stimuli–induced EEG features.

#### **Figure 13.**

*Stimulus induced evolving lateralized Rhytmic delta activity (Si-evolving LRDA) in a patient with SAH. Sternal Rub (red arrow) inducing right sided periodic spikes at 2 Hz. Also note the presence of rhythmic delta activity over the left side. SAH: subarachnoid hemorrhage.*
