Approach to the patient with transient alteration of consciousness

Efficacy of continuous electroencephalogram for the management of altered mental status in the neurosurgical intensive care unit

BACKGROUND

Continuous electroencephalograms (cEEGs) are often used in the neurosurgical intensive care unit (NSICU) to detect subclinical seizures (SCSs) in patients with altered mental status (AMS). This retrospective study evaluated the efficacy of this approach for improving patient outcomes.

METHODS

We reviewed the records of 100 patients admitted to the NSICU between 2015 and 2020 who underwent continous electroencephalograms (cEEG) during workup of unexplained AMS. Patient outcomes were classified as positive (discharged), neutral (transfer of care), or negative (dead). Incidence of SCSs on cEEG and association with patient outcomes was analyzed with Chi-square analysis and relative risk (RR).

RESULTS

For the 99 included patients, median age was 62 years and 43% were female. About 15.2% had a known or newly diagnosed brain tumor. Outcomes were positive in 22 patients, neutral in four, and negative in 73. SCSs were detected in 15 patients, of whom 12 died, two were discharged, and one whose care was transferred. Chi-square association between SCS and outcome (P = 0.59) and RR of death associated with SCS diagnosis (1.1) was not significant.

CONCLUSION

We found a lower incidence of SCSs (15.2%) than reported in the literature. In the absence of clinically evident seizures, continous cEEGs performed in the NSICU to determine the etiology of AMS did not yield an improvement in patient outcomes, and patients diagnosed and treated for SCS did not have statistically decreased risk of death. In summary, electroencephalogram monitoring for SCS is important but should not delay diagnosis and treatment of other, potentially life-threating etiologies of AMS.

Adult EEG

After more than 85 years of development and use in clinical practice, the electroencephalogram (EEG) remains a dependable, inexpensive, and useful diagnostic tool for the investigation of the electrophysiologic activity of the brain. The advent of digital technology has led to greater sophistication and multiple software applications to extend the utility of EEG beyond the confines of the laboratory. Despite the discovery of new waveforms, basic neurophysiologic principles remain essential to the clinical care of patients. Patterns in the interictal EEG make it possible to clarify the differential diagnosis of paroxysmal neurological events, classify seizure type and epilepsy syndromes, and characterize and quantify seizures when ictal recordings are obtained. EEG can also demonstrate cerebral dysfunction when structural imaging is normal to detect focal or lateralized abnormalities in patients with encephalopathy. High-density EEG with electrical source imaging has improved localization in candidates for epilepsy surgery. Quantitative EEG and broadband EEG are advancing our understanding of the functional processes of the brain itself.