Tau Deposition in Young Adults with Drug-resistant Focal Epilepsy

Objective: To evaluate the presence of tau deposition and pathologic features of chronic traumatic encephalopathy (CTE) in young adult patients treated with focal cortical resections for drug-resistant epilepsy.

Methods: Sixty consecutive patients who had undergone surgical treatment for drug-resistant focal epilepsy between 18 and 45 years of age were identified (2010-2017). Medical records were reviewed to determine clinical factors, including history of head trauma, age at seizure onset, age at surgical resection, seizure type(s) and frequency, imaging findings, and surgical outcome. All formalin-fixed, paraffin-embedded blocks from the surgical specimens from each subject were sectioned and stained with hematoxylin and eosin and antibodies to tau (Thermo Fisher Scientific Clone AT8), and examined blindly for tau pathology, including lesions characteristic 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. Although none of the patients had pathological findings characteristic of CTE, 23 patients (38%) demonstrated tau-immunoreactive lesions, including neurites, neurofibrillary pretangles, neurofibrillary tangles, subpial tau, and/or glial tau. In 4 of the 23 patients (7% of the cohort; 17% of those with tau pathology), substantial tau burden was identified. Three of these 4 patients had no significant history of head trauma; 1 patient had multiple sports-related concussions. No specific clinical factors correlated with the presence of tau pathology.

Significance: Tau-immunoreactive lesions were found in 38% of 60 patients who underwent a focal cortical resection for drug-resistant focal epilepsy. Diagnostic features of CTE were not detected in any patient; however, the pathological evaluation for CTE was limited to a surgical specimen. The prominent and excessive tau deposition in 23 patients (38%) is abnormal in this age group and warrants further investigation.