Increased Incidence of Epilepsy in a Brain Bank Alzheimer's Disease Cohort and Its Association With TDP-43 Pathology.

Aims: Evidence suggests Alzheimer's disease (AD) patients are at increased risk of epilepsy and that seizure incidence is associated with faster cognitive decline. Previous studies indicate hyperphosphorylated tau may play a role in this disease association; however, abnormal TDP-43 and α-synuclein deposition have not been extensively examined.

Methods: Clinical and neuropathological records of AD cases over a 5-year period were retrieved from the London Neurodegenerative Diseases Brain Bank. The 114 cases were categorised into three groups: AD plus epilepsy, AD plus hippocampal sclerosis (HS) and AD only. Semi-quantitative scores for tau, TDP-43 and α-synuclein pathology within the middle temporal gyrus, hippocampus and amygdala were compared between groups.

Results: A 12% incidence of epilepsy and/or epileptic symptomology was found among the cohort. Twelve cases (11%) showed HS. No significant difference in tau pathology scores was seen between groups. However, a significantly higher score for TDP-43 was seen in AD plus epilepsy compared with AD only in the middle temporal gyrus (p = 0.004). The burden of α-synuclein pathology was increased in the amygdala of AD plus epilepsy and AD plus HS.

Conclusions: The incidence of epilepsy within this AD cohort is higher than expected within the general population (even when matched for age), and this may be associated with increased TDP-43 burden. Understanding the relationship between AD and epilepsy may highlight mechanisms of cellular damage and tissue vulnerability.