White matter changes contribute to corpus callosum atrophy in the elderly: the LADIS study

Abstract

Background and purpose: The corpus callosum (CC) is the most important structure involved in the transmission of interhemispheric information. The aim of this study was to investigate the potential correlation between regional age-related white matter changes (ARWMC) and atrophy of CC in elderly subjects.

Materials and methods: In 578 subjects with ARWMC from the Leukoaraiosis And DISability (LADIS) study, the cross-sectional area of the CC was automatically segmented on the normalized midsagittal MR imaging section and subdivided into 5 regions. The ARWMC volumes were measured quantitatively by using a semiautomated technique and segmented into 6 brain regions.

Results: Significant correlation between the area of the rostrum and splenium regions of the CC and the ARWMC load in most brain regions was identified. This correlation persisted after correction for global atrophy.

Conclusion: Increasing loads of ARWMC volume were significantly correlated with atrophy of the CC and its subregions in nondisabled elderly subjects with leukoaraiosis. However, the pattern of correlation between CC subregions and ARWMC was not specifically related to the topographic location of ARWMC. The results suggest that ARWMC may lead to a gradual loss of CC tissue.

Fig 1.

The left panel shows axial views illustrating the delineation of 6 anatomic regions: frontal (green), parietal (turquoise), temporal (yellow), basal ganglia (red), occipital lobes (pink), infratentorial regions (purple); see details in text. The right panel shows the average distribution of ARWMC projected onto orthogonal sections of the group-averaged T2-weighted image. The color-coding indicates the frequency of ARWMC occurrence, ranging from 5% (dark blue) to 30% and above (dark red).

Fig 2.

Segmentation and subdivision of the CC area into 5 distinct subregions obtained from the normalized midsagittal T1 (MPRAGE) scans. A radial partitioning scheme is used for regional analyses of the CC. CC1 indicates rostrum and genu; CC2, rostral body; CC3, midbody; CC4, isthmus; CC5, splenium.

Fig 3.

The correlation between the area of each of the 10 CC subregions and the volume of ARWMC in each of 5 hemispheric regions and the whole brain. To obtain a better illustration of the regional specificity between CC atrophy and ARWMC, we subdivided the CC into 10 subregions and not 5 subregions as reported in Fig 2. The color code from blue to red indicates the magnitude of regression coefficients.

Fig 4.

Comparison of mean total callosal area measured on normalized MR imaging in nondisabled elderly subjects, classified by severity of ARWMC (Fazekas ratings 1, 2, and 3). Vertical bars indicate SDs. The white figures indicate the mean ARWMC volumes. Triple asterisks indicate P < .001 (ANOVA test).