Thalamic Involvement and Its Impact on Clinical Disability in Patients with Multiple Sclerosis: A Diffusion Tensor Imaging Study at 3T

BACKGROUND AND PURPOSE: Several studies suggest that grey matter involvement may play a role in multiple sclerosis (MS) pathology. Diffusion tensor imaging (DTI) at 3T was used to investigate the presence of damage to the normal-appearing thalamus in MS and its relationship with disability. MATERIALS AND METHODS: Twenty-four patients with relapsing-remitting (FIR, n = 13, age = 41.7 +/- 6.1, Expanded Disability Status Scale [EDSSI score = 2.2 +/- 1.2) and secondary-progressive (n = 11, age = 46.9 +/- 9.6, EDSS = 5.9 +/- 1.0) MS and 24 age- and sex-matched healthy volunteers were studied. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in regions of interest of normal-appearing thalamus. We examined group differences in MD and FA and correlations between DTI-derived metrics and clinical or imaging measures of disease. RESULTS: Patients with MS had higher thalamic FA (P < .0001) and MID (P = .035) than volunteers. MD values correlated with the Paced Auditory Serial Addition Task V = -0.43, P = .034) and motor EDSS (r = 0.47, P = .021) scores. In patients with RRMS, MID values correlated with global EDSS (r = 0.75, P = .003) and motor EDSS V = 0.68, P = .010). Correlations were found between MID values and T1 and T2 lesion load V = 0.58, P < .05) and brain parenchymal fraction V = -0.46, P < .05). CONCLUSIONS: DTI was able to detect abnormalities in normal-appearing thalamus of patients with MS. The strength of association between thalamic DTI measures and functional impairment was in the same range as those seen with standard MR imaging disease measures. The assessment of the integrity of the thalamus with DTI is a promising metric as a marker of disease for future studies.