Background and purpose: It has been suggested that subcortical lesions may influence cognitive performances at early stages of cognitive impairment but not in late stages of dementia. We aimed to test whether cognitive decline is associated with subcortical hyperintensities in patients with mild cognitive impairment (MCI).
Methods: We included 170 consecutive MCI patients (mean follow-up, 3.8+/-1.6 years). We assessed subcortical hyperintensities on a baseline magnetic resonance imaging scan with a semiquantitative rating scale. The mean annual cognitive decline was calculated with the Mini-Mental State Examination and the Dementia Rating Scale at baseline and the end of follow-up.
Results: Compared with patients whose cognitive performances remained stable or improved during follow-up, patients whose cognitive performances declined often had a larger amount (greater than the median of the distribution) of periventricular (PVH) (P=0.0005) and white-matter (P=0.02) hyperintensities. The rate of cognitive decline was higher with increasing PVH: mean change in the Mini-Mental State Examination score=0.16 vs -0.66 points/year in patients with PVH in the first versus third tertile (P=0.0002). The rate of decline in executive functioning was also higher with increasing PVH: mean change in the Dementia Rating Scale initiation subscore=-0.05 vs -1.42 points/year in patients with PVH in the first versus third tertile (P=0.04). These associations were independent of vascular risk factors, temporal lobe atrophy, and MCI subtype and were stronger in patients with baseline executive dysfunction.
Conclusions: White-matter hyperintensities and especially PVH were significantly associated with cognitive decline in MCI patients. This result was independent of the MCI subtype but stronger in cases of executive dysfunction at baseline.