Objective:
People with focal epilepsy experience one or more seizures prior to diagnosis. The Human Epilepsy Project (HEP) was a prospective study enrolling people with newly diagnosed focal epilepsy. It collected information including cognitive testing at the time of enrollment. This was completed utilizing a computerized test battery called the Cogstate Brief Battery (CBB). A prior analysis found that enrollment CBB test scores were below that of age matched controls and that performance on testing was not independently associated with the longer-term development of treatment resistance over the course of the HEP study. The present study assesses the impact of pretreatment seizures on cognition at time of diagnosis, considering time-to-treatment initiation in relation to seizure onset, pre-treatment seizure frequency, and pretreatment seizure classification.
Methods:
Participants with newly diagnosed focal epilepsy and no other major medical comorbidities or intellectual disability (estimated IQ > 70) were enrolled between June 29, 2012, and September 1, 2019. A subset of the 448 enrolled participants (N = 183) were over 18 years old, had complete HEP enrollment data that included pre-treatment seizure histories, and complete enrollment CBB testing for analysis in this study. Performance on enrollment CBB testing was modeled using multiple linear regression with pre-treatment seizure characteristics including seizure type and duration between seizure onset and treatment initiation, controlling for other key baseline participant characteristics.
Results:
There were no independent associations between cognitive measures on the CBB at the time of enrollment and pre-treatment seizures after correcting for potentially confounding variables. Z-scores for the attention composite on CBB (an average of Identification and Detection tests) were not associated with a global pre-treatment seizure score that quantified time with seizures (days) and seizure count by seizure type (motor, non-motor, bilateral tonic clonic) (p = 0.29). Similarly, z-scores for the memory composite (an average of the One Card Learning test and One Back tests) were not associated with the pre-treatment seizure score (p = 0.1). No additional independent associations were found to be significant between z-scores for attention or memory composites and other potential explanatory variables.
Significance:
This study highlights an important finding for people who develop focal epilepsy and otherwise are in good health: pre-treatment time-limited seizures do not have an independent impact on cognition early on, as measured by a brief validated cognitive screening test. This suggests that that cognition at the time of epilepsy diagnosis may be more strongly related to underlying etiology, chronic disease, and comorbidities.
