Abstracts

Rationale: Cognitive impairment in patients with drug-resistant focal epilepsy is frequent and the cause is not well understood. We hypothesized that memory deficits may occur in young adult patients with medically refractory focal seizures due to chronic traumatic encephalopathy (CTE) that may occur secondary to seizure activity. Methods: Sixty consecutive patients who underwent focal cortical resections for non-lesional intractable epilepsy between 18-45 years of age were identified (2010-2017). Medical records were reviewed to determine clinical factors including history of head trauma, age of seizure onset, age at epilepsy surgery, seizure-type(s) and frequency, imaging findings, and surgical outcome. Formalin fixed, paraffin-embedded blocks from the resections specimens from each subject were sectioned and stained with hematoxylin and eosin and tau (ThermoFischer Scientific Clone AT8, Rockford, IL), and examined blindly for tau pathology, including the pathognomonic lesions of CTE. Results: The median age at resection was 29.5 years (range 19-45). A history of head trauma was reported in 19 patients: mild head trauma/concussion without loss of consciousness in 12 and traumatic brain injury with loss of consciousness in 7. Twenty three patients (38%) demonstrated tau-immunoreactive lesions: including neurites, neurofibrillary pre-tangles, and neurofibrillary tangles. Four of the 23 patients (7% of the cohort; 17% of those with tau pathology) had a significant tau “burden.” Three of the 4 patients were aged 41-45 years and had no significant history of head trauma; a fourth had multiple sports-related concussions. However, none of the 60 patients demonstrated findings diagnostic of CTE. Conclusions: The present study limited to surgical pathology in 60 patients with drug-resistant focal epilepsy indicated that CTE could not be confirmed in this cohort. An important limitation of this study is that a definitive diagnosis of CTE requires a postmortem neuropathological examination. The prominent tau deposition in 23 patients is unusual in this age group and will require further investigation. Funding: Mayo Foundation