Relevance of functional neuroimaging in the progression of mild cognitive impairment.

Aim: To assess whether combining neuropsychological tests and cerebral blood flow markers improves progression accuracy from mild cognitive impairment (MCI) to Alzheimer's disease (AD) than each of them on its own.

Methods: Forty-two patients were investigated prospectively, undergoing baseline and 3-year follow-up neuropsychological tests and neuroimaging with Tc-ECD-SPECT. Twenty-one patients had developed AD while 21 retained their initial diagnosis. The relative blood flow and cognitive differences were studied. Validity parameters, multivariant analysis and logistic regression model were calculated.

Results: Patients who deteriorated showed lower scoring than stable subjects in some neuropsychological tests (p = 0.03-0.001) and in relative blood flow in selected regions (8-10%). Low cognitive test scoring and low relative blood flow in some regions showed sensibilities and specificities from 70% to 86% for the diagnosis of early Alzheimer's disease. The relative risk of progression to AD was up to 4.7 times higher for these patients (p = 0.0001). The left frontal relative blood flow, the CAMCOG and orientation scoring were the best data to predict the risk of progression to AD.

Conclusions: The combination of functional imaging and neuropsychological tests can diagnose with high sensitivity and specificity if a patient is suffering cognitive impairment in its early stages, and may aid in predicting the risk of developing dementia.