Relationship between hippocampal volume and CA1 neuron loss in brains of humans with and without Alzheimer's disease.

Hippocampal volumetry has been proposed to aid in the early diagnosis of Alzheimer's disease (AD) and to monitor progression of the disease. While this is believed to be as a result of hippocampal neuron loss, this association has not been firmly established and loss of other tissue elements may be responsible for the observed atrophy. We investigated the relationship between neuron loss and hippocampal volume in 11 patients with autopsy-confirmed AD and 11 non-demented age-matched controls. Strong correlations were found between neuron number and both hippocampal volume and brain volume demonstrating that volume and neuron content are related in normal subjects and that the relationship is maintained in AD. In AD, neuron number and volume measures significantly decline with increasing disease duration. These findings support the suggestion that hippocampal atrophy in AD is as a result of neuron loss and confirm the usefulness of volumetry as an indirect measure of neurodegeneration in this disease.