Cognitive and functional neuroimaging correlate for anosognosia in mild cognitive impairment and Alzheimer's disease.

OBJECTIVES

To investigate the correlation between anosognosia and behavioural symptoms, performance on executive tests, and frontal cortex regional cerebral blood flow (rCBF) in patients with 'amnestic mild cognitive impairment' (MCI) and mild Alzheimer's disease (AD).

METHODS

From a prospective Memory Clinic cohort including consecutively referred patients, age 60 years or above, and with MMSE score 20 or above, 36 patients with AD and 30 with MCI were included in this study. Anosognosia was assessed using a categorical scale and discrepancy scores between patients' and relatives' reports on a 20-item Memory Questionnaire (MQ). Behavioural symptoms were assessed with Frontal Behavioural Inventory (FBI). Executive functions were examined with a range of neuropsychological tests. Tc99m-HMPAO SPECT was obtained in an unselected sample of 55 of the 66 patients, and rCBF was analysed in six cortical frontal regions.

RESULTS

Insight was equally impaired in the two patient groups. A significant correlation was found between impaired awareness and dementia severity (MMSE). Discrepancy-scores on the MQ were significantly correlated to scores on FBI and to rCBF in the right inferior frontal gyrus, but not to executive tests. The groups classified by the categorical ratings 'full', 'shallow' and 'no' awareness were not characterized by differences in behavioural symptoms, executive performance or frontal rCBF.

CONCLUSIONS

Impaired awareness is associated with behavioural symptoms and may reflect functional impairment in the right inferior frontal cortex.