The yield of routine electroencephalography in the detection of incidental nonconvulsive status epilepticus – A prospective study

ObjectiveDiagnosis of NCSE is challenging, because the clinical presentation ranges from minimally altered mental status to coma without tonic–clonic activity. According to the largest retrospective study to date the incidence of NCSE is about 0.2%.MethodsWe prospectively investigated electroencephalography (EEG) recordings of 2514 consecutive patients that were referred to the Electrophysiology Unit of Department of Neurology, Vienna General Hospital between November 2009 and February 2011 (i.e. 16 months).ResultsThe incidence of NCSE in our study population was 0.8%, i.e. the EEG of 19 patients fulfilled the criteria of NCSE. In 53% of these patients the NCSE was not suspected by treating physicians. A severely reduced level of consciousness was found in 78% of patients with a suspected NCSE and in 30% of patients with an unsuspected NCSE, although the results were not statistically significant (p = 0.081). The delay between the admission to the hospital and diagnosis ranged between 0 and 51 days.ConclusionsNCSE was an unsuspected finding in more than half of the patients. Consciousness was severely impaired in only one third of these patients.SignificanceThese results highlight the importance of urgent EEG for the diagnosis of NCSE in patients even without significant impairment of consciousness.