Cortical high-frequency oscillation loops initiate spasm seizures

Area of Science:

• Neuroscience
• Epileptology
• Clinical Neurology

Background:

• Epileptic spasms can manifest as focal-onset seizures, but the underlying cortical network remains poorly understood.
• Investigating the neural mechanisms of focal-onset epileptic spasms is critical for developing targeted therapies.

Purpose of the Study:

• To elucidate the cortical network dynamics during focal-onset epileptic spasms.
• To identify the specific electrophysiological signatures and functional network changes associated with spasm seizures.

Main Methods:

• Analysis of electrocorticography (ECoG) power spectra and dynamic functional network changes in four patients with focal-onset epileptic spasms.
• Intracranial electrode implantation and focal resection surgery were performed.
• Investigation focused on high-frequency activity in gamma and ripple bands during interictal and preictal periods.

Main Results:

• Electrocorticography power in the resected zone peaked before seizure onset, notably in gamma and ripple bands.
• Dynamic functional network analysis revealed distinct patterns of high-frequency activity involving the resected zone, sensorimotor cortex, and other regions.
• Information flow patterns shifted significantly between interictal and preictal states, particularly in the gamma and ripple bands.

Conclusions:

• The sensorimotor cortex plays a requisite role in the initiation of spasm seizures.
• A ripple activity loop between the resected zone and sensorimotor cortex, augmented by gamma activity loops for spread, may underlie seizure onset and propagation.