MR Diffusion Tractography to Identify and Characterize Microstructural White Matter Tract Changes in Systemic Lupus Erythematosus Patients

Abstract

Systemic lupus erythematosus (SLE) is a predominantly female autoimmune disease that can affect the central nervous system. Neuropsychiatric symptoms are found in 25-70% of SLE patients. Using diffusion tensor imaging, various studies have reported changes in white matter integrity in SLE patients with neuropsychiatric symptoms (NPSLE patients). The purpose of this study was to investigate if changes can be detected in the individual white matter tracts in SLE patients regardless if neuropsychiatric symptoms are present or not. Magnetic resonance diffusion tractography in several individual white matter tracts that are involved in language and memory tasks, including tracts to cortical association areas, was applied in 21 patients with NPSLE (mean age: 40.7 ± 12.8 years; range: 22-67 years), 18 patients with non-neurologic systemic lupus erythematosus (non-NPSLE) (mean age: 40.6 ± 12 years; range: 22-67 years), and 20 healthy control (HC) individuals (mean age: 40.64 ± 12.7 years; range: 19-60 years). Additional patients were evaluated; however, because of the inability to complete the scans required, they were excluded from the study. The fractional anisotropy of individual fiber tracts was measured and correlated with cognitive function and lupus disease severity index (Systemic Lupus Erythematosus Disease Activity Index [SLEDAI]) to assess predictability and diagnostic value of these measures for NPSLE. Analyses of variance of the tractography data from the analysis of 21 tracts revealed decreased fractional anisotropy in uncinate fasciculus in the NPSLE patients when compared to non-NPSLE lupus patients and HC individuals (P = 0.002). Non-NPSLE patients also demonstrated decreased fractional anisotropy when compared to healthy patients (P = 0.03). Decreased fractional anisotropy was also identified in the corpus callosum and corona radiata in NPSLE patients when compared to HC individuals; however, these tracts did not show a significant difference between NPSLE and non-NPSLE patients. Decreased fractional anisotropy in the uncinate fasciculus correlated with low SLEDAI score (R2 = 0.32). Diffusion tensor tractography corroborates findings of decreased white matter integrity within the anterior corona radiate as well as the corpus callosum as previously described. Specifically, our study identified changes in the uncinate fasciculus in NPSLE and non-NPSLE patients that correlate with clinical changes (SLEDAI scores) and are independent of conventional T2 lesion burden.