Is there a clustering effect on electroencephalographic seizure localization?

Area of Science:

• Neurology
• Epileptology
• Clinical Neurophysiology

Background:

• Long-term video-EEG monitoring (LTM) is crucial for localizing seizures in epilepsy surgery candidates.
• Previous research on seizure clustering and its effect on localization has produced conflicting results.
• Understanding seizure origin is vital for effective treatment of medically intractable epilepsy.

Purpose of the Study:

• To investigate whether seizure clustering influences the accuracy of brain region localization during LTM.
• To determine if clustered seizures arise from the same focus as sporadically occurring seizures.
• To assess the impact of seizure timing on diagnostic localization in epilepsy.

Main Methods:

• An observational study analyzed 479 LTMs with 2774 focal seizures over 6 years.
• Sequential focal seizure pairs were classified based on EEG localization concordance (same focus, same hemisphere, or other).
• Statistical analysis (ANOVA) compared localization concordance across different interseizure intervals and subgroups.

Main Results:

• No significant difference in EEG localization concordance was found between clustered and sporadic seizure pairs (p=0.47).
• Defining concordance by hemisphere lateralization also showed no significant difference (p=0.34).
• Subgroup analyses of multifocal, bilateral, and extratemporal seizures yielded similar non-significant results.

Conclusions:

• Seizure clustering does not alter the localizing value of EEG findings in LTM.
• Focal seizures provide consistent localization whether they occur in clusters or sporadically.
• These findings may support potentially shorter LTM durations for epilepsy presurgical evaluation.