Microphysiology of epileptiform activity in human neocortex

Area of Science:

• Neuroscience
• Epileptology
• Biomedical Engineering

Background:

• Medically refractory epilepsy requires advanced monitoring techniques.
• Standard electroencephalography (EEG) lacks the spatial resolution to pinpoint seizure origins.
• Understanding the micro-scale origins of epileptic activity is crucial for developing targeted therapies.

Purpose of the Study:

• To characterize fine-resolution electrocortical activity (microEEG) in the human epileptogenic cortex.
• To investigate the spatial extent and nature of epileptic discharges at a micro-scale.
• To explore the role of micro-scale activity in seizure initiation and propagation.

Main Methods:

• Implantation of a 96-microelectrode array (16 mm², 400 µm spacing) in five epilepsy patients.
• Simultaneous recording of microEEG alongside standard intracranial EEG.
• Analysis of high-spatial-resolution data to identify localized epileptic events.

Main Results:

• MicroEEG detected localized discharges resembling interictal epileptiform activity (microdischarges) and electrographic seizures (microseizures).
• These events were confined to cortical regions as small as 200 µm².
• In two patients, micro-scale activity was implicated in seizure initiation or propagation.

Conclusions:

• Small cortical domains generate microdischarges and microseizures, forming the substrate of epileptogenic cortex.
• MicroEEG provides unprecedented spatial resolution for studying epilepsy.
• These findings suggest a critical role for micro-scale cortical dynamics in seizure generation and propagation.