Interictal infraslow activity in patients with epilepsy

Area of Science:

• Neuroscience
• Epileptology
• Electroencephalography (EEG)

Background:

• Interictal infraslow activity (ISA) is a distinct electrophysiological phenomenon.
• Its potential diagnostic utility in epilepsy has not been fully explored using conventional EEG systems.

Purpose of the Study:

• To determine if interictal infraslow activity (ISA), obtainable from standard EEG, offers insights into the epileptogenic process.
• To assess the feasibility of detecting ISA in routine clinical EEG recordings.

Main Methods:

• Analysis of long-term intracranial EEG recordings from 12 epilepsy patients.
• Inclusion of long-term scalp EEG recordings from 3 additional patients.
• Evaluation of ISA using an XLTEK system.

Main Results:

• ISA background activity was higher during waking states compared to sleep.
• Focal ISA changes, with millivolt amplitudes in intracranial and microvolt in scalp recordings, were intermittently observed.
• These focal changes were not always contiguous to adjacent channels or the epileptogenic zone.

Conclusions:

• Interictal ISA is detectable with conventional intracranial and scalp EEG, without specialized DC amplifiers.
• ISA provides supplementary information valuable for pre-surgical epilepsy evaluation.
• Assessment of ISA may benefit patients with other neurological disorders and healthy volunteers.