Morphological patterns of seizures recorded intracranially

Area of Science:

• Neuroscience
• Clinical Neurology
• Epileptology

Background:

• Understanding the electroencephalography (EEG) characteristics of seizure onset is crucial for localizing the seizure focus.
• Pathological substrate plays a significant role in seizure generation and EEG manifestations.

Purpose of the Study:

• To analyze the frequency and morphological characteristics of initial EEG seizure manifestations.
• To correlate these EEG features with pathological findings in temporal and extratemporal epilepsy.

Main Methods:

• Analysis of EEG data from depth and subdural electrodes in 26 epilepsy patients undergoing resective surgery.
• Correlation of EEG seizure onset characteristics (frequency, periodic spikes) with post-surgical pathological analysis of the seizure onset zone.

Main Results:

• Medial temporal lobe seizure onset, particularly with mesial temporal sclerosis, frequently exhibited high-frequency ( > 13 Hz) EEG discharges and preceding periodic spikes.
• Extratemporal seizure onset associated with structural lesions showed lower-frequency ( < 13 Hz) EEG activity and lacked preceding periodic spikes.
• Seizure onset frequency variability was characteristic of temporal lobe seizures but not extratemporal seizures.

Conclusions:

• EEG seizure onset characteristics are distinct between temporal and extratemporal epilepsy and are influenced by underlying pathology.
• High-frequency, spiky EEG patterns are indicative of medial temporal lobe epilepsy with sclerosis.
• Low-frequency EEG patterns without preceding spikes may suggest an extratemporal origin with a pathological substrate.