Lateralized Periodic Discharges: Which patterns are interictal, ictal, or peri-ictal?

Area of Science:

• Neurology
• Neurophysiology
• Critical Care Medicine

Background:

• Lateralized Periodic Discharges (LPDs) are EEG patterns with debated significance, potentially indicating brain injury or ictal activity.
• Distinguishing between interictal and ictal LPDs is crucial for patient management, particularly in critically ill individuals.

Purpose of the Study:

• To propose criteria for differentiating LPDs that reflect irritative brain injury from those associated with seizures (peri-ictal).
• To introduce a specific subtype, LPDs-max, as an ictal pattern indicative of focal non-convulsive status epilepticus.

Main Methods:

• Review and propose a classification system for LPDs based on EEG morphology and clinical correlation.
• Define LPDs-proper, LPDs-plus (including triphasic morphology), and LPDs-max patterns.
• Emphasize the integration of clinical, neuroimaging, and EEG data for accurate interpretation.

Main Results:

• LPDs can be categorized along an interictal-ictal continuum, with 'peri-ictal' LPDs temporally linked to seizures.
• LPDs-max, characterized by periodic polyspike-wave or burst-suppression-like patterns with posterior predominance, represents an ictal pattern.
• LPDs-max is often refractory to antiseizure medications and may be associated with subtle motor signs.

Conclusions:

• A nuanced approach is needed to interpret LPDs, moving beyond a simple dichotomous classification.
• The proposed criteria, including LPDs-max, aid in identifying ictal patterns and guiding management in critically ill patients.
• A comprehensive clinical approach, integrating EEG with neuroimaging and clinical context, is essential for accurate diagnosis and treatment.