MRI Might Detect Late-Onset Alzheimer Disease Decades Before Symptoms Start

Anthony L. Komaroff, MD reviewing Kunz L et al. Science 2015 Oct 23.

Adults who carry the APOE-?4 mutation show impaired grid-cell activity on functional magnetic resonance imaging.

In people who are destined to suffer from late-onset Alzheimer's disease (AD), the entorhinal cortex begins to develop deposits of tau protein by age 30. Grid cells that help humans navigate in space are associated closely with the entorhinal cortex (a brain area in the medial temporal lobe), and grid-cell activity can be assessed by functional MRI (fMRI).

A multicenter European team studied 38 healthy young adults who carried one copy of the APOE-?4 gene (a risk factor for late-onset AD) and 37 similar volunteers who carried no copies. fMRI (blood oxygenation level-dependent [BOLD] type) revealed that the high-risk group had impaired grid-cell activity and elevated hippocampal activity. The investigators interpreted the elevated hippocampal activity as compensating for difficulties in spatial navigation. The APOE-?4 carriers also demonstrated deficits in tests of spatial navigation.

Citation(s):

Kunz L et al. Reduced grid-cell-like representations in adults at genetic risk for Alzheimer's disease. Science 2015 Oct 23; 350:430.