Right hippocampus atrophy is independently associated with Alzheimer's disease with psychosis

The purpose of this study was to determine whether regionally distributed medial temporal cortex thickness (or hippocampal volume) and frontal lobe volume are independently associated with the onset of Alzheimer's disease (AD) with psychosis.

We identified 26 AD patients with psychosis (AD+P) and 48 AD patients without psychosis (AD-P) from the Memory Impairment Clinic at Pusan National University Hospital in South Korea. They were matched for age, gender, duration of AD, and Clinical Dementia Rating sum of box score. All participants met the National Institute of Neurological and Communication Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria for probable AD. Psychosis was diagnosed according to Jeste and Finkel's proposed diagnostic criteria for psychosis of AD. All participants underwent 3-T magnetic resonance imaging, and 3-D magnetization-prepared rapid gradient echo sequence was acquired for each. The FreeSurfer version 5.1 software package was used to analyze cortical thickness and volume on 3-D T₁ -weighted images. anova was used to investigate the differences in cortical thickness and the volume of the total frontal cortex, total temporal cortex, and subregions of the medial temporal cortex between groups after age, gender, years of education, Clinical Dementia Rating sum of box score, duration of AD, and total intracranial volume were controlled for. Furthermore, we added the total frontal volume as an additional variable to investigate whether the association between the medial temporal cortex and AD+P is independent of the frontal cortex.

We found that both left and right hippocampal volume were smaller in AD+P than in AD-P. In particular, there was a significant difference in right hippocampal volume between the AD+P and AD-P groups after total frontal volume was added as an additional variable.

We found that more severe hippocampal atrophy is associated with AD+P than with AD-P. In addition, atrophy of the right hippocampus remained significant among AD+P after adjustment for frontal volume. These findings suggest that right hippocampal atrophy is independently associated with AD+P.