Putting Electroencephalography (EEG) in the Emergency Department

Approximately, 4% and 10% of emergency department (ED) patients in the United States present with altered mental status (AMS). According to previous studies, close to 30% of AMS cases occur due to neurological etiologies. Among these pathologies are non-convulsive seizures (NCS) and non-convulsive status epilepticus (NCSE). In our previous study, the investigators established that approximately 4% (95% confidence interval, 2-8%) of ED patients with AMS suffer from NCS and NCSE. Our study also revealed that 78% of the ED patient with AMS have some form of EEG abnormality.

NCS and NCSE are difficult to diagnose especially in AMS patients because performing a thorough physical examination or obtaining medical history is often impossible in altered patients. Definitive diagnosis of NCS/NCSE requires electroencephalography (EEG), a test that records brain electrical activity and provides information about the brain function.

Unfortunately, obtaining an EEG in the ED can be challenging. This requires transporting an EEG machine to patient's bedside, where space limitations and presence of variety of monitors and devices, especially in over-crowded EDs render this practice difficult. In many institutions an EEG service is not offered after work hours due to the unavailability of 24/7 EEG technologist coverage and real-time electroencephalographer interpretation. As a result of the aforementioned limitations, ED physicians may refrain from ordering EEG.

The wireless portable EEG device (microEEG) designed by the Bio-Signal Group was designed to address these limitations. With minimal training, ED personnel could use this small, microEEG device to obtain an EEG. The recording then can be wirelessly transmitted to a host computer via a secure network connection to the neurology experts who could interpret the EEG. Incorporating microEEG in the initial workup of patients with AMS could help the ED attending rule out NCS/NCSE and focus on other diagnoses. Alternatively, if the presence of NCS is confirmed by EEG, the treatment could be initiated early and potentially reduce morbidity or mortality.

The investigators hypothesize that incorporating EEG in the work of ED patients with AMS could impact the management(diagnosis and treatment)of these patients and influence their clinical outcome.

Sample size: Our sample size analysis using data one published related study reveled that the study would need 65 patients in each group (total n:130). However, the investigators plan to perform an interim analysis after enrolling half of this target sample and adjust the sample size calculation based on the collected data if necessary.

Inclusion criteria

ED patients ≥ 18 years old with AMS.

Exclusion criteria

• Patients with apparent and immediately correctable cause of AMS (determined by ED attending during initial evaluation) that include:

• Fingerstick or serum glucose less than 60mg/dl
• Hypothermia (Hypothermia is defined as any body temperature below 35.0 C [95.0 F]).
• Hyperthermia, heat exhaustion or heat stroke
• Opioid overdose responding to Narcan.
• Patients who cannot undergo EEG recordings for any reason (e.g. severe scalp injury).
• Hemodynamically unstable patients(SBP <90mm Hg)
• Patients who are uncooperative or combative.
• Patients transferred out of ED before enrollment.
• Patients with obvious tonic-clonic or focal seizures in the ED.

Note: Patients with hypoglycemia who do not return to their baseline level of mental status within 30 minutes of correcting their blood glucose level, will be enrolled. Similarly, patients who had an obvious seizure in the ED but do not return to their baseline mental status within 15 minutes will also be enrolled.