Invasive seizure monitoring in the critically-Ill brain injury patient: Current practices and a review of the literature

Seizures commonly occur in a variety of serious neurological illnesses, and lead to additional morbidity and worsened outcomes. Recently, it has become clear that not all seizures in the acute brain injury setting are evident on scalp EEG. To address this, we have developed a protocol for depth electrode placement in the neuro-intensive care unit for patients in whom the clinical suspicion of occult seizures is high. In the current manuscript, we review the literature on depth EEG monitoring for ictal events in critically-ill, unconscious patients, focusing on the incidence of seizures not detected with scalp EEG in various conditions. We critically discuss evidence in support of and against treating these events that are only detectable on depth recordings. We describe additional specific scenarios in which depth EEG recordings may be helpful, including for the detection of delayed cerebral ischemia following subarachnoid hemorrhage. We then describe current techniques for bedside electrode placement. Finally, we outline potential avenues for future investigations, including the use of depth electrodes to describe circuit abnormalities in acute brain injury.