Gamma network topology and pathological changes in drug-resistant
temporal lobe epilepsy with cognitive deficits
Abstract
Temporal lobe epilepsy (TLE) is the most common form of adult epilepsy,
frequently accompanied with cognitive deficits. The present study aims
to investigate functional network alterations affected by cognitive
impairments in drug-resistant TLE. Patients with drug-resistant TLE were
divided into normal cognition (NC) and abnormal cognition (AC) groups
based on their primary medical history and completed the Wechsler
intelligence scale. Thirty-one patients in the NC group and 30 in the AC
group had mean intelligence quotients (IQ) of 107 (96-137) and 71
(60-85), respectively. Eighteen controls were enrolled in the study.
Graph theory analysis showed decreased alpha small world index (SWI) in
the AC group compared to that in the NC group and controls. Increased
SWI in the fast rhythm was observed in both TLE groups compared with
controls. But the gamma SWI in the AC group declined and was
significantly lower than in the NC group at 50–70 Hz. A lower IQ is
associated with a decreased SWI in alpha and 50-70Hz. Spectral analysis
revealed reduced alpha power and increased delta power in the TLE groups
compared to the controls. Immunofluorescence analysis revealed more
severe amyloid-β (Aβ) and phosphorylated Tau (p-Tau) loads in the
resected hippocampus of the AC group than that of NC group. Cognitive
deficits in drug-resistant TLE are associated with general EEG activity
slowing, loss of efficiency in gamma connectivity, and increased Aβ and
p-Tau expression. These alterations are potential markers and
intervention targets for concomitant cognitive decline in drug-resistant
epilepsy.