Commonalities and distinctions of static and dynamic functional connectivity density between left and right temporal lobe epilepsy

To comprehensively examine static and dynamic functional connectivity density (FCD) in left temporal lobe epilepsy (LTLE) and right temporal lobe epilepsy (RTLE). For 46 LTLE patients, 43 RTLE patients, and 53 healthy controls (HCs), T1-weighted structural images and resting-state functional images were collected. Static FCD and corresponding temporal dynamic FCD (dFCD) obtained via a sliding window approach were measured and compared. Additionally, seed-based functional connectivity (FC) analysis was executed. Relationships between cognitive scores and FCD or dFCD values were analyzed. Compared with HCs, LTLE and RTLE patients presented reduced static FCD values in the ipsilateral lateral temporal lobe. However, for LTLE, the FCD in the lateral temporal lobe contralateral to the epileptic focus also decreased. In RTLE patients, the FCD and dFCD in the left occipital lobe increased, whereas the dFCD in the left cerebellum decreased. FC analysis (seed: left middle temporal gyrus) demonstrated that LTLE patients had a wider range of aberrant brain regions than RTLE patients did. However, the left occipital lobe-based FC reductions were detected only in the RTLE patients. FCD and dFCD revealed moderate discrimination abilities between LTLE and RTLE. This study reveals that while both LTLE and RTLE share reduced static FCD in the ipsilateral temporal lobe, indicating common global network impairment, they exhibit distinct disruption profiles: LTLE presents more bilateral and widespread alterations, whereas RTLE specifically involves the occipital lobe and cerebellum. These findings consolidate TLE as a system-level disorder with lateralized network phenotypes. Integrating static and dynamic FCD provides a comprehensive framework for elucidating whole-brain network abnormalities and the associated pathophysiological and compensatory mechanisms in TLE.