Exploratory study of peripheral immune changes associated with diffusion MRI multi-compartment model in temporal lobe epilepsy.

Objective: Studies in temporal lobe epilepsy (TLE) have shown that focal inflammation is a key contributor to seizure initiation and maintenance. However, most in vivo studies to date have focused on positron emission tomography (PET) findings. In this exploratory study, we assessed the relationship between multicompartment Neurite Orientation Dispersion and Density Imaging (NODDI) measures (FISO [extracellular/free water], FICVF [neurite density], and ODI [neurite dispersion]) and peripheral immune cells and inflammatory biomarkers. We hypothesized that these biomarkers would be associated with NODDI abnormalities in the affected temporal lobe (aTL).

Methods: Eighteen patients with TLE and 18 age-matched healthy participants underwent 3 Tesla magnetic resonance imaging (MRI) high angular resolution diffusion imaging. TLE participants also provided peripheral blood samples. We generated NODDI parameter maps (FISO, FICVF, and ODI) and compared the groups using voxelwise two-sample t tests with corrections for multiple comparisons (p < .05), focusing on temporal regions. In TLE patients only, NODDI values extracted from significant clusters correlated with peripheral inflammatory biomarkers.

Results: ODI increases in the aTL significantly correlated with pro-inflammatory cytokines such as interleukin (IL)-1α and IL-2. FICVF was lower in the aTL, and this decrease correlated with IL-27 and CD3⁺, CD8⁺, and Th17 T-cell responses. FISO was increased in the aTL, and this increase correlated with CXCL10 expression and immune cells such as CD3⁺, CD8⁺, and Th1 T cells. In addition, FISO was increased in other areas of the affected and unaffected temporal lobes, but this increase was not correlated with any of the biomarkers tested.

Significance: Group differences indicate a significant relationship between NODDI biomarkers of injury/neuroinflammation and peripheral immune cells and pro-inflammatory biomarkers in aTL. These novel in vivo findings support further the development of NODDI as a promising non-invasive technique for visualizing neuroinflammation. Further validation of NODDI may enable clinicians to use this approach for monitoring disease progression and treatment response in epilepsy, potentially leading to more personalized treatment strategies.