Clinical and Radiological Differences in Alzheimer's Disease with and without a History of Mild Cognitive Impairment

We assessed the influence of a history of amnesic mild cognitive impairment (MCI) in patients with Alzheimer's disease (AD) at presentation from a clinical and radiological point of view. A consecutive sample of patients fulfilling the criteria of probable Alzheimer's disease according to the NINCDS-ADRDA work group not previously diagnosed nor treated underwent neuropsychological assessment including mini-mental test, Blessed dementia rating scale (BDRS), ADAS-Cog, neuropsychiatric inventory (NPI), and a daily living activities scale (DAD). Radiological evaluation consisted of magnetic resonance imaging, left hippocampal volumetry and magnetic resonance spectroscopy (MRS) of the brain. We divided the patients into two groups according to positive/negative history of MCI for a period longer than one year. The AD patients with a history of MCI were more likely to have a history of depression (OR: 5.5; 95% CI: 1.12-26) and have more depressive symptoms at presentation in the NPI than those without a history of MCI. They also had a history of hypertension more frequently than the remainder. The presence/absence of ApoE4 alleles did not have influence in the clinical course. With regard to radiological findings the patients with previous MCI showed lower values of N-acetyl-aspartate (NAA) in parietal (p=0.0001) temporal (p=0.08) and occipital (p=0.00001) lobes than the other group, as well as a smaller left hippocampus although the difference was not statistically significant. A history of MCI in AD patients represents a form of the disease with slower progression from clinical and radiological viewpoints. These patients present with more depressive symptoms and a history of depression than the remainder. The lower NAA levels on MRS are compatible with a longer disease duration when AD is preceded by amnesic MCI.