MCI is considered a steppingstone between normal cognitive aging and AD. The lateral and medial tracts of the NBM, which is the hub of the cortical cholinergic network, present with reduced integrity in both MCI and AD. However, there is still a lack of clarity of the relationship between white matter integrity of the NBM tracts and conversion from MCI to AD.

Preliminary analysis consisted of 72 participants from the Alzheimer’s Disease Neuroimaging Initiative database who underwent diffusion weighted imaging at multiple timepoints over at least 5 months. Participants were split into 54 MCI non-converters and 18 MCI converters to AD. The mean diffusivity (MD) values for the lateral and medial tracts were extracted using a previously validated NBM tract template. The percent change in NBM tracts’ MD over time was calculated, and the slope was then compared between groups.

MCI converters showed a significant increase in the slope of percent change of MD (0.17 ± 0.11) compared to MCI non-converters (0.082 ± 0.24, p<0.01). In the medial tract there was no significant increase found between the MCI converters (0.12 ± 0.21) and MCI non-converters (0.084 ± 0.27).

MCI converters show a greater loss of integrity of the NBM lateral tract over time as they convert to AD compared to MCI non-converters. However, no difference is observed in the medial tract. This data suggests that the lateral tract degenerates more rapidly than the medial tract in MCI to AD progression.