Prediction of AD with MRI-based hippocampal volume in mild cognitive impairment

To test the hypothesis that MRI-based measurements of hippocampal volume are related to the risk of future conversion to Alzheimer's disease (AD) in older patients with a mild cognitive impairment (MCI). Patients who develop AD pass through a transitional state, which can be characterized as MCI. In some patients, however, MCI is a more benign condition, which may not progress to AD or may do so slowly. Eighty consecutive patients who met criteria for the diagnosis of MCI were recruited from the Mayo Clinic Alzheimer's Disease Center/Alzheimer's Disease Patient Registry. At entry into the study, each patient received an MRI examination of the head, from which the volumes of both hippocampi were measured. Patients were followed longitudinally with approximately annual clinical/cognitive assessments. The primary endpoint was the crossover of individual MCI patients to the clinical diagnosis of AD during longitudinal clinical follow-up. During the period of longitudinal observation, which averaged 32.6 months, 27 of the 80 MCI patients became demented. Hippocampal atrophy at baseline was associated with crossover from MCI to AD (relative risk [RR], 0.69, p = 0.015). When hippocampal volume was entered into bivariate models-using age, postmenopausal estrogen replacement, standard neuropsychological tests, apolipoprotein E (APOE) genotype, history of ischemic heart disease, and hypertension-the RRs were not substantially different from that found univariately, and the associations between hippocampal volume and crossover remained significant. In older patients with MCI, hippocampal atrophy determined by premorbid MRI-based volume measurements is predictive of subsequent conversion to AD.