Ictal 1.5-Tesla MR imaging with arterial spin labeling perfusion imaging in three patients with electrographic seizures diagnosed with routine electroencephalography based on the ACNS Critical Care EEG Terminology 2021

Abstract

Background: The 2021 version of the Standardized Critical Care EEG Terminology published by the American Clinical Neurophysiology Society (ACNS 2021) specifies the diagnostic criteria for non-convulsive status epilepticus (NCSE) using continuous electroencephalographic (cEEG) monitoring. Since few facilities have access to cEEG, routine EEG, which can only be performed during consultation hours, is generally used for emergencies. We examined if the diagnostic ability is enhanced by adding arterial spin labeling (ASL) perfusion imaging to 1.5-Tesla magnetic resonance imaging (MRI). Patients and Methods: Eighty EEGs, performed on patients with neurological emergencies for 2 years, were reviewed which included three patients diagnosed with electrographic seizures (ESz). Results: Based on the ACNS21, EEG could diagnose Esz, but could not diagnose NCSE, being a 30-minute recording. In contrast, ASL clearly identified focal, ictal hyperperfusion. The signal intensity was maximized at a post-labeling delay (PLD) of 1.5-1.75 s. The signal intensity gradually decreased. However, even at a PLD of 2.0 s, the intensity remained strong in areas with a close anatomical relationship to the epileptogenic lesions. Further, the same region showed high signal intensity on diffusion-weighted imaging (DWI). Conclusion: Although ESz can be diagnosed based on the ACNS 2021 using EEG alone, diagnosing NCSE can be challenging. Therefore, our suggestion is to initially perform MRI to capture the hemodynamics of ictal hyperperfusion using ASL with multiple PLDs, and monitor the coupling state of metabolism and blood flow with DWI. Finally, an accurate pathophysiological diagnosis of NCSE should be confirmed by EEG.