Altered mental status is a common chief complaint in the emergency setting, and the initial evaluation often fails to find an etiology. Subclinical (electrographic) seizures and nonconvulsive status epilepticus (NCSE) are potential causes of delirium and altered mental status, but require electroencephalogram (EEG) for diagnosis. It is not clear how often subclinical seizure or NCSE is present in those with undifferentiated altered mental status, nor which patients are most likely to benefit from emergent EEG. We performed a retrospective review of patients presenting to a single academic medical center emergency department (ED) over a one-year period with the chief complaint of “altered mental status” who had an order placed for EEG while in the ED. During the study period 112 patients met inclusion criteria. Of the 112 patients, 10 (8.9%) had seizures observed on EEG. Of these patients with EEG-observed seizure, 4 (40%) had clinical correlates, whereas the remaining 6 (60%) had no clinical manifestation of seizure. Five (50%) had a final diagnosis of status epilepticus, all of which had subtle or absent clinical correlates qualifying for NCSE. Eighty-one (72%) patients had abnormal EEG findings, 27 (24%) of whom had epileptiform EEG findings without definitive seizure. The median times from ED presentation to EEG being ordered and completed were 6.4 and 20.9 h, respectively. EEGs obtained in patients with undifferentiated altered mental status are typically abnormal and are frequently of clinical importance. Seizure was observed in a substantial portion of these, often without clinical signs. The average time until EEGs were ordered and completed were about 6 and 20 h respectively; as a result, time sensitive clinical decisions that need to be made within 20 h may often be made without information from the EEG. More urgent EEG may benefit patients with altered mental status of unclear etiology in the ED.
Runcie et al. (Thu,) studied this question.