Caudate nuclei volume, diffusion tensor metrics, and T(2) relaxation in healthy adults and relapsing-remitting multiple sclerosis patients: implications for understanding gray matter degeneration.

Purpose: To investigate the utility of caudate nuclei (CN) macro- and microstructural metrics as markers of gray matter degeneration in healthy adults and relapsing-remitting multiple sclerosis (RRMS) patients.
Materials and Methods: The normal age- and pathology-related changes in caudate nuclei volume (CNV), the corresponding diffusion tensor metrics, and the T(2) relaxation times were measured in a cohort of 32 healthy adults (12 men/20 women; age range 21-59 years) and 32 age-matched RRMS patients (8 men/34 women; age range 21-57 years).
Results: Smaller values in both the absolute CNV and the caudate volume ratio relative to the total intracranial volume (CNVp) were observed in the RRMS group relative to healthy controls. The fractional anisotropy (FA), based on the diffusion tensor imaging (DTI) of the CN increased with age in healthy adults (r = 0.52; P = 0.003) but not in patients (r = 0.28; P = 0.12). The caudate FA value was approximately 9% larger in RRMS patients relative to controls (P = 0.001). The mean diffusivity of the CN was greater in the RRMS group compared to controls (P = 0.02). The caudate T(2) relaxation times were smaller in the RRMS group relative to the control group (3% reduction, P = 0.05). T(2) relaxation times did not exhibit age-related changes (P > 0.35) in either cohort. Strong and significant correlations between CNVp and whole-brain lesion load (r = -0.48; P = 0.005) and whole-brain CSF fraction (r = -0.46; P = 0.01) were also noted.
Conclusion: These preliminary findings indicate that caudate DTI-derived metrics can serve as potential quantitative radiological markers of MS pathology.