Hyperphosphorylated Tau in Mesial Temporal Lobe Epilepsy: a Neuropathological and Cognitive Study

Area of Science:

• Neurology
• Neuroscience
• Pathology

Background:

• Temporal lobe epilepsy (TLE) frequently causes cognitive deficits, but the underlying neuronal mechanisms are not fully understood.
• Existing research often analyzes older individuals, making it difficult to distinguish epilepsy-related changes from age-related neurodegeneration.
• This study investigates neuropathological changes in younger adults with TLE to clarify epilepsy-specific mechanisms.

Purpose of the Study:

• To investigate the neuropathological basis of cognitive deficits in adults with mesial TLE younger than 60 years.
• To examine the presence and burden of amyloid-beta (Aβ), hyperphosphorylated tau (p-tau), and TAR DNA-binding protein-43 (TDP-43) in TLE hippocampi.
• To correlate neuropathological findings with cognitive performance and seizure frequency.

Main Methods:

• Neuropathological examination of hippocampal formations from 22 adults with drug-resistant mesial TLE and 20 age- and sex-matched controls.
• Immunohistochemistry was performed for Aβ, p-tau, and TDP-43, followed by quantitative analysis.
• Patients underwent comprehensive pre-surgical neuropsychological evaluations.

Main Results:

• Hippocampal formations in TLE patients showed a significantly higher burden of p-tau compared to controls.
• Amyloid-beta deposits and abnormal TDP-43 inclusions were not found in either group.
• Higher p-tau burden correlated with impaired attention and increased seizure frequency.
• Patients with hippocampal sclerosis (HS) type 2 exhibited higher p-tau immunostaining than those with HS type 1.

Conclusions:

• In adults younger than 60, increased p-tau burden in mesial TLE is associated with attention deficits and higher seizure frequency.
• Tau pathology may contribute to cognitive impairment in TLE, independent of typical aging or Alzheimer's disease markers.
• These findings highlight tau pathology as a potential target for understanding and treating cognitive deficits in TLE.