Objective:

To investigate the role of cerebellum in the epileptic network, the prevalence and clinical significance of crossed cerebellar diaschisis (CCD) in patients with hippocampal sclerosis (HS)-related temporal lobe epilepsy (TLE).

Background:

The cerebellum has been increasingly recognized as an important structure involved in epileptic networks. CCD is a phenomenon characterized by decreases in metabolism and perfusion in the cerebellar hemisphere contralateral to a unilateral supratentorial lesion. Although CCD has been extensively reported in various supratentorial disorders, the prevalence of CCD in TLE with HS remains unclear.

Design/Methods:

We retrospectively analyzed 95 adults with pathologically confirmed HS-related TLE. Preoperative FDG-PET images were normalized and quantified as standardized uptake value ratios (SUVr) using the whole grey matter as the reference. The cerebellum was parcellated into subregions of interest SUIT-cerebellum atlas. Bilateral cerebellar hemispheres and each pair of symmetric regions of interest (ROIs) were extracted to calculate an asymmetry index (AI). CCD was defined as positive when the absolute AI exceeded 0.1.

Results:

The cohort (35 men and 60 women) included 48 right-sided and 47 left-sided HS. Mean seizure onset age was 15.6 ± 10.2 years old and the average disease duration was 18.7 ± 11.9 years. Among 78 patients with ≥2 years of follow-up, 63(81%) achieved Engel class I. The mean absolute AI across cerebellar hemisphere was 0.0166 ± 0.0136 (range: 0.0003-0.0707). ROI-based analysis using the SUIT cerebellar atlas revealed generally low interhemispheric asymmetry across all subregions. The highest mean absolute AI values were found in lobule VIIb (0.0310 ± 0.0235), crus I (0.0376 ± 0.0292), and lobule IX (0.0331 ± 0.0251).

Conclusions:

In our cohort of HS-related TLE, no significant evidence of CCD was observed under FDG-PET–based asymmetry analysis. The absence of CCD in this cohort indicates that metabolic alterations in TLE are primarily confined to the epileptic network, without notable contralateral cerebellar involvement.