| Summary: | 博士 === 高雄醫學大學 === 醫學研究所 === 99 === Brain features of late-life major depressive disorder are atrophy and ischemic change, particularly in the frontostriatal circuit and hippocampus. Patients with late-life depression may present various patterns of cognitive impairment which may persist even after successful antidepressant treatment. Proton magnetic resonance spectroscopy (1H MRS) is a newly magnetic resonance imaging (MRI) technique and is widely used to detect certain biochemicals, including N-acetyl-L-aspartate (NAA)、total creatine/phosphocreatine (tCr)、choline-containing compounds (choline)、and myo-inositol。 The aims of this study were 1) to investigate the 1H MRS features of late-life major depressive disorder at the depressive state；2) to investigate the 1H MRS features of late-life major depressive disorder in remission, and illustrate their association with cognitive impairments.
Case-control study designs were adopted. There were two study samples for the study. The first one recruited 27 elders with major depressive disorder and 19 comparisons. The second one were 130 elders with major depressive disorder in remission and 100 comparisons. All study participants of the first part completed MRI and 1H MRS, while 96 cases and 60 comparisons of the second part did. Comprehensive neuropsychological tests were administrated and diagnostic criteria of mild cognitive impairment (MCI) were used to subtype those cases into no MCI, amnestic MCI (aMCI), and non-amnestic MCI (naMCI).
Unmedicated patients with late-life major depressive disorder had a significantly lower NAA/tCr in the frontal lobe, and higher choline/tCr and myo-inositol/tCr in the basal ganglia than the comparisons. The myo-inositol/tCr correlated with global cognitive function among the patients. Among the remitted patients, 52.3% met the definition of MCI, including 28.5% with aMCI and 23.8% with naMCI. Even in remission, the patients showed lower NAA and higher choline and myo-inositol in the basal ganglia, lower NAA and higher myo-inositol in the frontal lobe, and higher myo-inositol in the hippocampus. Subtype of aMCI was associated with ventricular atrophy and higher myo-inositol in the hippocampus, while naMCI was associated with lower NAA in the basal ganglia and frontal lobe and higher myo-inositol in the basal ganglia.
Brain abnormality persists after remission of depressive symptoms. The brain characteristics of subtype of aMCI were suggested the prodromal of dementia. The main change of naMCI located at frontal lobe and basal ganglia. In conclusion, brain biochemical changes of the elders with major depressive disorder at both depressive and remitted states. High rate of MCI occurred in the late-life major depressive disorders even in remission. Different subtypes of MCI related to late-life major depressive disorder presented different pathophysiological change in the frontostriatal circuit and hippocampus.
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