Amnestic mild cognitive impairment : Structural MRI findings predictive of conversion to Alzheimer ’ s disease

Background and Purpose: Mild cognitive impairment (MCI) is by many considered a prodromal phase of Alzheimer’s disease (AD). We used voxelbased morphometry (VBM) to find out whether structural differences on MRI could offer insight about the development of clinical AD in patients with amnestic MCI at three years follow-up. Methods: Twenty-four amnestic MCI patients were included. After three years 46% had progressed to AD (n=11, age [72.7, SD 4.8]; sex [women/men] 8/3). For 13 patients (age [72.4, SD 8.6]; sex [women/men] 10/3) the diagnosis remained MCI. Baseline MRI at 1.5T included a coronal heavily T1-weighted 3D gradient echo sequence. Localized grey matter differences were assessed with VBM. Results: The converters had less grey matter volume in medial (including the hippocampus) and lateral temporal lobe structures, parietal lobe structures and lateral temporal lobe structures. After correction for age, gender, total grey matter volume and neuropsychological evaluation, left-sided atrophy remained statistically significant. Specifically, converters had more left parietal atrophy (angular gyrus and inferior parietal lobule) and left lateral temporal lobe atrophy (superior and middle temporal gyrus) than stable MCI patients. Conclusion: By studying two MCI populations, converters versus non-converters, we found atrophy beyond the medial temporal lobe to be characteristic of MCI patients who will progress to dementia. Atrophy of structures such as the left lateral temporal lobe and left parietal cortex may independently predict conversion.