Impact of White Matter Lesions and Cognitive Deficits on Conversion from Mild Cognitive Impairment to Alzheimer's Disease

Mild cognitive impairment (MCI) may represent a prodromal stage of dementia and confers a particularly high annual risk of 10-15% for conversion to Alzheimer's disease (AD). Recent findings suggest that white matter lesion pathology (WML) can negatively influence conversion from MCI to AD. In this study, we examined the predictive value of neuropsychological test results and WML pathology on conversion of MCI to AD. Retrospective neuropsychological and magnetic resonance imaging data were collected for MCI patients seen at the University Clinic of Innsbruck between 2005 and 2011. WML were visually rated using the Fazekas and Scheltens scales. Of the 60 subjects, 31 converted to AD during a follow-up of 18.3 +/- 7.4 months and 29 remained stable. Orientation, MMSE score, word list learning and recall, visual memory, and naming scores were significantly lower in MCI patients converting to AD than in non-converters. Converters had significantly higher Fazekas scores and more WML in periventricular regions. Periventricular WML were negatively associated with psychomotor speed, and subcortical WML were negatively correlated with visual memory at baseline in all MCI patients. Low scores in orientation and verbal delayed recall were predictors of progression from MCI to AD. Periventricular WML correlate with lower cognitive function in patients with MCI. However, deficits in orientation and verbal memory, but not vascular changes, turned out as predictive for conversion from MCI to AD. Consequently, a higher WML burden may represent a serious risk factor but not an early symptom for the imminent conversion to AD.