EEG infraslow activity in absence and partial seizures

Area of Science:

• Neuroscience
• Clinical Electrophysiology
• Epileptology

Background:

• Conventional assumption: DC-coupled amplifiers are necessary for recording infraslow activity (ISA).
• ISA's potential clinical utility in epilepsy diagnosis and surgical planning requires further investigation.
• Limited understanding of ISA characteristics in different seizure types.

Purpose of the Study:

• To demonstrate that ISA can be recorded using conventional EEG filter settings.
• To explore the clinical usefulness of ISA in characterizing absence and partial seizures.
• To evaluate ISA's role in determining seizure onset and differentiating seizure types.

Main Methods:

• Archived EEG data from 6 children with absence seizures and 10 adults with partial seizures were analyzed.
• Seizures were evaluated using conventional filter settings, full band, and a specific 0.01-0.1 Hz filter for ISA.
• Data analyzed using BESA software for topographic analysis of ISA patterns.

Main Results:

• A 0.01-0.1 Hz filter setting provided better ISA assessment than the full band.
• Absence seizures exhibited bilateral, synchronous ISA with specific frontal and posterior polarity sequences.
• Partial seizures showed ISA corresponding to the hemisphere of onset, with potential electrode displacement noted.
• Two types of ISA topography were identified: focal spread only, and focal spread with frontal synchrony.
• ISA analysis helped differentiate focal seizures from those with a generalized seizure tendency.

Conclusions:

• ISA can be effectively recovered from conventional EEG recordings, challenging the need for specialized DC-coupled amplifiers.
• ISA analysis aids in accurately determining seizure onset areas and differentiating focal from generalized seizure patterns.
• These findings have significant implications for surgical planning in epilepsy, especially when structural lesions are absent.