Diagnostic Value of Electroencephalography with Ten Electrodes in Critically Ill Patients

Abstract

Background: In critical care settings, electroencephalography (EEG) with reduced number of electrodes (reduced montage EEG, rm-EEG) might be a timely alternative to the conventional full montage EEG (fm-EEG). However, past studies have reported variable accuracies for detecting seizures using rm-EEG. We hypothesized that the past studies did not distinguish between differences in sensitivity from differences in classification of EEG patterns by different readers. The goal of the present study was to revisit the diagnostic value of rm-EEG when confounding issues are accounted for. Methods: We retrospectively collected 212 adult EEGs recorded at Massachusetts General Hospital and reviewed by two epileptologists with access to clinical, trending, and video information. In Phase I of the study, we re-configured the first 4 h of the EEGs in lateral circumferential montage with ten electrodes and asked new readers to interpret the EEGs without access to any other ancillary information. We compared their rating to the reading of hospital clinicians with access to ancillary information. In Phase II, we measured the accuracy of the same raters reading representative samples of the discordant EEGs in full and reduced configurations presented randomly by comparing their performance to majority consensus as the gold standard. Results: Of the 95 EEGs without seizures in the selected fm-EEG, readers of rm-EEG identified 92 cases (97%) as having no seizure activity. Of 117 EEGs with "seizures" identified in the selected fm-EEG, none of the cases was labeled as normal on rm-EEG. Readers of rm-EEG reported pathological activity in 100% of cases, but labeled them as seizures (N = 77), rhythmic or periodic patterns (N = 24), epileptiform spikes (N = 7), or burst suppression (N = 6). When the same raters read representative epochs of the discordant EEG cases (N = 43) in both fm-EEG and rm-EEG configurations, we found high concordance (95%) and intra-rater agreement (93%) between fm-EEG and rm-EEG diagnoses. Conclusions: Reduced EEG with ten electrodes in circumferential configuration preserves key features of the traditional EEG system. Discrepancies between rm-EEG and fm-EEG as reported in some of the past studies can be in part due to methodological factors such as choice of gold standard diagnosis, asymmetric access to ancillary clinical information, and inter-rater variability rather than detection failure of rm-EEG as a result of electrode reduction per se.

Practical Considerations When Performing Neurodiagnostic Studies on Patients with COVID-19 and Other Highly Virulent Diseases

“…Electrode placement will be documented in the EEG per ACNS guideline 1. • Depending on the patient's clinical presentation, a minimum of 8 electrodes will be used with the following electrodes (see Appendix B, Figure B2) preferred due to their ease of application and relative high utility in screening for clinically relevant EEG abnormalities as shown by other authors Westover et al 2020).…”

“…In addition, for these studies, the authors believe the modifications will lead to a reduced exposure time without a clinically relevant compromise in EEG quality. Based on previous studies, the reduced electrode array has been shown to have high specificity but limited sensitivity Westover et al 2020). The electrode choice is an evolving process for us, and additional electrodes could be applied as needed.…”

“…• A reduced array of disposable electrodes (ACNS March 25, 2020) will be applied with paste and tape instead of collodion; in addition, applying a head wrap will be considered to help secure the electrodes. • A minimum of 8 electrodes will be used, with the following electrodes ( Figure B2) preferred due to their ease of application and relative high utility in screening for clinically relevant EEG abnormalities as shown by other authors Westover et al 2020).…”

Monitoring the Burden of Seizures and Highly Epileptiform Patterns in Critical Care with a Novel Machine Learning Method

“…The Rapid-EEG system lacks midline and parasagittal electrodes, and consequently a focal seizure that is highly localized to the parasagittal region would not be detected by Rapid-EEG or identified by Claritγ (although prior research [37][38][39] has argued that this lack of coverage might not significantly impact its sensitivity in critical care and emergency medicine settings).…”

Epileptic Seizures in Critically Ill Patients: Diagnosis, Management, and Outcomes

“…While the contribution of continuous electroencephalographic monitoring is intuitively obvious, we should also progress in demonstrating its superiority when compared to the sequential approach [ 11 ]. Additional questions should be addressed, like who must do it [ 12 , 13 , 14 ], with which equipment and technics types [ 15 , 16 ], using which electroencephalographic montages [ 17 ], for how long, within which emergency time frame [ 14 ], and ultimately for which specific patient population [ 18 ]?…”