Seizure Cycles in Focal Epilepsy

Area of Science:

• Neurology
• Epilepsy Research
• Chronobiology

Background:

• Focal epilepsy is defined by recurrent seizures, but the prevalence and patterns of these seizure cycles are not well understood.
• Seizure recurrence exhibits cyclical patterns, influencing patient outcomes and treatment strategies.

Purpose of the Study:

• To determine the prevalence, strength, and temporal patterns of seizure cycles in focal epilepsy.
• To investigate seizure cycles across various timescales, from hours to years.

Main Methods:

• Retrospective analysis of continuous intracranial electroencephalography (cEEG) and seizure diary data from 222 adults with focal epilepsy.
• Quantification of seizure cycles using phase-locking value (PLV) and identification of seizure chronotypes.
• Analysis of interictal epileptiform activity (IEA) cycles to understand underlying biological rhythms.

Main Results:

• High prevalence of seizure cycles: 89% circadian, 60% multidien, and 12% circannual.
• Circadian and multidien seizure cycles demonstrated significant strength (PLV ≈ 0.34), while circannual cycles were weaker (PLV ≈ 0.17).
• Seizures consistently occurred during specific phases of interictal epileptiform activity cycles, indicating predictable timing.

Conclusions:

• This study establishes the high prevalence of multiple seizure cycles in focal epilepsy, explaining seizure timing variability.
• Findings suggest potential for optimizing diagnostic study scheduling, time-varying therapies, and clinical trial designs in epilepsy.
• Understanding seizure chronotypes can lead to more personalized and effective epilepsy management strategies.