Qualitative magnetic resonance imaging findings in geriatric depression. Possible link between later-onset depression and Alzheimer's disease?

BACKGROUND: Several clinical and neuroimaging investigations support the notion that underlying brain changes may relate to depression in older patients, especially those with a later-age initial episode. However uncertainty still exists about diagnostic and pathogenic significance of structural brain abnormalities in aged depressives, in part because many studies lack all-elderly and age-similar normal comparison populations.
METHODS: Brain morphology of elderly depressives (N = 30) and normal controls (N = 36) was compared by assessing magnetic resonance imaging (MRI) brain scans with qualitative criteria-based scales. Ratings included lateral and third ventricle enlargement, and cortical, medial temporal, and caudate atrophy.
RESULTS: Significant differences between depressed and control groups were not demonstrated. Later-onset depressives had significantly more left medial temporal and left caudate atrophy than early-onset counterparts of similar age. Medial temporal atrophy significantly correlated with cognitive impairment and was not related to physical illness. Depressives with medial temporal atrophy (N = 7) were older and had later age at onset of depression than those without such changes. Cerebrovascular disease risk factors did not predict MRI abnormalities.
CONCLUSIONS: Results indicate non-specificity and lack of homogeneity of qualitatively measured structural brain changes in geriatric depression, but suggest that pathology of specific, lateralized brain regions may be implicated in some later-onset patients. The relationship between medial temporal atrophy and late-onset depression raises the possibility that such patients may suffer from as-yet undeclared Alzheimer's disease. Lack of association between cerebrovascular disease risk factors and brain changes suggests other pathophysiological contributions.