The spectrum of indications for ultralong-term EEG monitoring.

Purpose: We assessed clinical cases to investigate the spectrum of indications for ultra-longterm EEG monitoring using a subcutaneous implantable device in adult patients with focal epilepsy.

Methods: Electronic charts were reviewed from patients undergoing ultra-longterm recordings at the European Epilepsy centers Barcelona, Freiburg and Vienna. Specific patient settings approached in the three centers were analyzed, and the main clinical question was extracted. Results from recordings were analyzed based on the specific results and information obtained.

Results: 24 patients in whom ultra-longterm recordings were available were analyzed. A total of 11 main indications for subcutaneous long-term EEG recordings were identified, including the identification of active epilepsy in patients with low seizure frequency, under- and overreporting of patients, differentiation of non-epileptic from epileptic events, assessment of seizure severity, circadian and multidian rhythms of seizure occurrence, validation of treatment efficacy, improvement of patient-based reporting and medicolegal evidence for seizure freedom. This is reported with patient-specific case vignettes.

Conclusion: Ultra-longterm monitoring using subcutaneous implantable EEG devices can provide relevant diagnostic and treatment information in a large spectrum of clinical situations. This is discussed considering the intrinsic limitations of the method related to spatial coverage, sensitivity and validity as a biomarker of ongoing seizures.