Relationship between Microstructural Degeneration of the Corpus Callosum, White Matter Hyperintensities, and Motor Function in Cognitively Intact Elderly

Abstract

Age-related changes in cerebral white matter, such as decreased corpus callosum (CC) volume and the presence of periventricular white matter hyperintensities (PVWMH) on fluid attenuated inversion recovery (FLAIR) MRI sequences have been demonstrated in nondemented elderly and are associated with motor impairment. Diffusion tensor imaging (DTI) can potentially detect microstructural white matter changes prior to macrostructural volume change. Examination of the relationship of microstructual CC degeneration detected by DTI, PVWMH's and motor function in cognitively intact elderly may suggest a structural-functional connection to this pathology. 14 cognitive intact (CDR = 0, mean MMSE 29.5) elderly men and women (mean age 80.2, range 70 - 92) underwent 3T MRI and detailed neurological evaluation, including fine motor and balance testing. WMH volumes were obtained with FLAIR sequences and were adjusted for intracranial volume. CC microstructural integrity was assessed using fractional anisotrophy (FA) from DTI (TR = 9500 ms; TE = 95 ms; slice thickness 2.0 mm; 20 non-collinear directions). For each subject, a 24 mm2 region of interest was placed in the CC genu (figure) . Relationships between WMHs, CC integrity, and motor function were examined using multivariate analyses adjusted for age. Greater age was associated with decreased CC genu FA (R2 = 0.41, p = 0.01) and total CC volume (R2 = 0.37, p = 0.02). Neither total nor anterior CC volume was associated with motor test performance. %PVWMH volume was associated with slower finger tapping (R2 = 0.23, p = 0.08), but was not associated with one leg standing (OLS). After adjusting for age and %PVWMH, decreased CC genu FA was associated with slower finger tapping (p = 0.02). After adjusting for age, decreased CC genu FA was associated with OLS with eyes open (p = 0.03 left; p = 0.02 right), and OLS with eyes closed (p = 0.07). Advanced age is associated with microstructural degeneration of the anterior corpus callous that disrupts fine motor skills and balance function in cognitively intact elderly, independent of WMH's or CC atrophy. Identification of risk factors to prevent such white matter change is needed to preserve motor abilities in our elderly population