Cognitive functions and white matter tract damage in amyotrophic lateral sclerosis: a diffusion tensor tractography study

Abstract

Background and purpose: ALS is predominantly a disease of the motor system, but cognitive and behavioral symptoms also are observed. DT MR imaging is sensitive to microstructural changes occurring in WM tracts of patients with ALS. In this study, we investigated the association between cognitive functions and extramotor WM tract abnormalities in ALS patients.

Materials and methods: DT MR imaging was obtained from 16 nondemented patients with ALS and 15 healthy controls. Patients with ALS underwent a neuropsychologic and behavioral evaluation. DT tractography was used to asses the integrity of the CST, corpus callosum, and the major long-range association tracts. The relationship between DT MR imaging metrics and cognitive functions was tested by using linear model analyses, adjusting for age and clinical disability.

Results: Eleven patients (69%) scored below the fifth percentile in at least 1 cognitive test, and 2 of them had a mild executive impairment. Performances at tests assessing attention and executive functions correlated with DT MR imaging metrics of the corpus callosum, CST, and long association WM tracts bilaterally, including the cingulum, inferior longitudinal, inferior fronto-occipital, and uncinate fasciculi. Verbal learning and memory test scores were associated with fornix DT MR imaging values, whereas visual-spatial abilities correlated with left uncinate fractional anisotropy.

Conclusions: WM tract degeneration is associated with neuropsychologic deficits in patients with ALS. DT tractography holds promise to gain insight into the role of the brain WM network abnormalities in the development of cognitive impairment in patients with ALS.

Fig 1.

Correlations between performances at the TMT (part A, part B, and difference between performance times of part B and part A) and FA of the corpus callosum, corticospinal tract, right inferior longitudinal fasciculus, and left inferior fronto-occipital fasciculus in patients with ALS. For illustrative purpose, the left column shows the reconstructions of the WM tracts in a single healthy control (tracts are superimposed onto the mean FA image). The right columns show the scatterplots of the correlations; FA values are reported on the x-axis (β, regression coefficient; partial R², proportion of variability accounted for by the given DT MR imaging variable); P_FDR, P values adjusted for multiple comparisons controlling for the false discovery rate.