Mohammed T. Abou-Saleh

356 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYdementia have significant atrophy of the frontal lobes. This can beeasily visualized using MRI and quantitated if need be. Patientswho have significant Alzheimer’s disease (AD) will demonstrateobservable hippocampal atrophy. Over time this can be measuredand utilized for assessing the progression of the disease. MRI canbe acquired with a different contrast, as noted earlier, and in threedimensions. Utilizing this one can develop specific methods toidentify objects of interest and quantitate these objects. Fluidmeasurements of cerebrospinal fluid in different locations can alsobe easily measured. The technique also seems to be of particularuse in mild cognitive impairment, in which commencing atrophy,especially of the hippocampus and temporal cortex, are oftenseen.SILENT INFARCTSAnother area of growing interest in geropsychiatry is theidentification of silent infarct or leukoencephalopathy. These area function of aging. The risk factors are very similar to those ofstroke, including high blood pressure, diabetes, etc. These changesare usually present in the deep white matter, the periventricularregion, and subcortical nuclei such as the caudate putamen andthalamus. These silent strokes occur at the ends of the perforatingblood vessels of the brain. These blood vessels do not havecollaterals and are therefore more susceptible to the developmentof occlusions and the ischaemia that results from them. Thesesilent strokes have been characterized pathologically as areas ofmyelin pallor, true infarcts (dead tissue and lacuna). A lacuna isdistinguished by the presence of fluid inside the area and this canbe determined by a bright signal on T2 and a dark signal on theT1 images. These changes have been related to depression, bipolardisorder and dementia. They are present in both AD and vasculardementia. The contributing role of these factors in AD iscontroversial. Epidemiological studies indicate that the presenceand extent of these changes is a good indicator of a developmentof dementia and it has the same odds ratio as APO-E studies.In summary, MRI is widely utilized to study various types ofneuropsychiatric disorders. It has particular application andutility for identifying pathology and atrophy in the context ofdementia, and lesions such as silent strokes in late-life depressionand late-life bipolar disorder.REFERENCEFor a more thorough update, see Krishnan KR, Doraiswamy PM. BrainInjury in Clinical Psychiatry. New York: Marcel Dekker, 1997.