White matter change in brain was described as leukoaraiosis in 1970s (CT Scan) and as unidentified bright objects (UBO) in 1980s (MR). In the last 20 years many studies were conducted to understand the significance of these changes.Improvements in imaging techniques ( FLAIR, magnetization transfer imaging,diffusion weighted and diffusion tensor imaging etc) have also contributed to the growing knowledge base. O’Brien JT review the field in this article.
Cross sectional studies have shown that white matter changes are associated with cognitive impairment, ( attention and executive function), gait and balance problems, urinary problems (including incontinence), other neurologic signs and symptoms, and depression. White matter lesions are associated with functional impairment.
Longitudinal studies like LADIS study (a pan european study) showed that presence ,particularly of severe, white matter change at baseline was strongly and independently associated with progression to disability, dementia, and death. Interesting finding for psychiatrists was that white matter changes at baseline were shown to predict both depressive symptoms and depressive episodes 3 years later.The observation that depression at baseline did not predict progression of white matter change over a 3-year period show that white matter changes predate and predict depression.
The pathological mechanisms of these links are not clearly understood. White matter lesions are usually classified in to periventricular lesions & deep white matter lesions. Pathological mechanisms suggested are different for these two.Deep lesions are thought to be related to vascular events ( like ‘incomplete infarcts’ ).
Late life depression is associated with atrophic changes in brain, how much this is in tandem with white matter changes is not known. White matter changes may reflect Wallerian type degeneration secondary to neuronal loss. It is also possible that the gray matter atrophy is secondary to disconnection from white matter pathology .Longitudinal studies using modern techniques combined with pathologic analysis would help us understand the nature, pathology and interrelationships better.
Summary of the article:
Clinical significance of white matter changes. O’Brien JT.Am J Geriatr Psychiatry. 2014 Feb;22(2):133-7.