Loss of callosal fibre integrity in healthy elderly with age-related white matter changes.

Age-related white matter changes (ARWMC) appear to correspond to a continuum from normal functioning to clinically overt neurological syndromes. Disturbance of the structural integrity of cerebral fibre tracts-the so-called cerebral network-by ARWMC might be one explanation for this development. From 3 T magnetic resonance imaging (MRI) data of 34 healthy elderly subjects (60-82 years) we calculated the lesion volume of ARWMC and the area of the corpus callosum (CC). Gait, balance and cognition were assessed. We compared these findings in those with mild (n = 22) and advanced (n = 12) ARWMC and performed tract-based spatial statistics (TBSS) to analyze white matter structural integrity. In subjects with advanced ARWMC, TBSS showed a significant decrease of fractional anisotropy (FA) in several large tracts of the white matter including the CC; total CC, CC2 and CC5 areas were significantly smaller. Despite these morphological changes, tests of gait, balance and cognition as measured by the Mini-Mental State Examination (MMSE) were in the normal range for both groups; only the Montreal Cognitive Assessment (MoCA) detected executive and language dysfunction in those with advanced ARWMC. Loss of tissue integrity and atrophy of the CC secondary to spatially remote lesions in the peri- and paraventricular white matter in ARWMC appear to be already detectable in healthy elderly individuals.