Diagnostic yield of continuous electroencephalographic monitoring in critically ill patients: a prospective cohort study

Abstract

Background: Continuous electroencephalographic monitoring has become an essential diagnostic tool in the evaluation of critically ill neurological patients. Electrographic seizures and nonconvulsive status epilepticus frequently occur without overt clinical manifestations, making detection based solely on bedside examination unreliable. Previous studies have reported electrographic seizures in approximately 10–30% of patients undergoing continuous electroencephalographic monitoring in intensive care units. Despite increasing implementation of this technique, real-world data regarding diagnostic yield and electroencephalographic findings in critically ill populations remain limited. Objective: To evaluate the diagnostic yield of continuous electroencephalographic monitoring and characterize electroencephalographic abnormalities in critically ill patients. Methods: Prospective cohort study including 173 critically ill patients undergoing continuous electroencephalographic monitoring for clinical indications such as unexplained alteration of consciousness, suspected seizures, abnormal movements, or investigation of encephalopathy. Continuous recordings were obtained using the international 10–20 electrode system and interpreted by experienced neurophysiologists. Clinical variables and electroencephalographic findings including background abnormalities, epileptiform activity, and electrographic seizures were analyzed. Results: Among the 173 patients included, 95 (54.9%) were female and 76 (43.9%) were male, with a mean age of 54.4 ± 22 years. Diffuse encephalopathy represented the most frequent electroencephalographic abnormality. Severe encephalopathy was identified in 53 patients (30.6%), moderate encephalopathy in 26 (15.0%), and mild encephalopathy in 12 (6.9%). Interictal epileptiform abnormalities were observed in 84 patients (48.6%). Electrographic seizures occurred in 35 patients (20.2%). Among these, 21 patients (12.1%) had purely electrographic seizures, 10 (5.8%) had electroclinical seizures, and 4 (2.3%) demonstrated both patterns. Conclusion: Continuous electroencephalographic monitoring demonstrated substantial diagnostic yield, detecting electrographic seizures in approximately one fifth of critically ill patients. These findings highlight the importance of electroencephalographic monitoring for identifying clinically occult seizures and guiding neurological management in intensive care populations.