Selective cognitive impairment during focal and generalized epileptiform EEG activity

Area of Science:

• Neuroscience
• Clinical Neurophysiology
• Cognitive Psychology

Background:

• Generalized epileptiform electroencephalogram (EEG) discharges, even without overt clinical changes, are linked to transitory cognitive impairment (TCI).
• Existing psychological tests for TCI are often impractical for routine clinical use due to short administration times and the tests' ability to suppress discharges.

Observation:

• Developed novel, engaging short-term memory tasks using verbal and nonverbal television game formats, suitable for extended patient participation (up to an hour or longer).
• Studied 46 patients with subclinical EEG discharges, rigorously screened for overt clinical changes during monitoring.
• Assessed TCI using video monitoring before and during testing to ensure accurate performance evaluation.

Findings:

• Transitory cognitive impairment (TCI) was demonstrable in 50% of patients with subclinical EEG discharges, with a 10% confidence level.
• EEG discharges during stimulus presentation significantly disrupted performance, while discharges during response periods had no demonstrable effect.
• A significant association was observed between the laterality of focal or asymmetrical generalized discharges and specific task impairment: left-sided discharges correlated with verbal task deficits, and right-sided discharges with nonverbal task deficits.

Implications:

• The developed TV game-based memory tasks offer a clinically applicable method for detecting TCI associated with subclinical epileptiform EEG discharges.
• Findings highlight the potential for medication to improve cognitive functioning in patients whose TCI is linked to subclinical discharges.
• Further prospective studies are necessary to quantify the prevalence of TCI-related disabilities and the efficacy of pharmacological interventions.