Review Article - Continuous EEG monitoring in the evaluation of non-convulsive seizures and status epilepticus

Non-convulsive seizures (NCSzs) and non-convulsive status epilepticus (NCSE) occur in a substantial proportion of patients with acute brain injury. These acute seizure disorders are often unrecognized and under-diagnosed. Seizure semiology of NCSz is too subtle clinically to be noticed. Most often, mental status impairment is the presenting feature. Changes in the functions of the thalamo-cortical system in patients with impaired consciousness can be detected by continuous EEG (cEEG) monitoring. cEEG monitoring allows detection of the changes at a reversible stage, often when there are no clinical indications of such phenomena. In addition EEG provides reasonable spatial resolution and excellent temporal resolution. This makes cEEG an excellent method for supplementing single or serial recordings in the detection of NCSzs and NCSE. Recent advances in digital EEG have made cEEG monitoring in the neurological intensive care unit (NICU) technically feasible. Current evidence suggests that the common clinical denominator associated with electrographic seizures or NCSzs is mental status impairment. In NCSE, the duration of ictal activity and the time of delay to diagnosis are independent predictors of poor outcome. It will be prudent to do cEEG monitoring in any patient with impaired consciousness either in the setting of acute brain injury or with no clear explanation to detect NCSzs/NCSE. Early recognition and timely intervention is likely to be associated with good outcomes.

Keywords
Non-convulsive seizures, Non-convulsive status epilepticus, Status epilepticus, Electrographic seizures, Electroencephalogram, Continuous EEG monitoring