January 03, 2013

White Matter Changes in Alzheimer's Disease

What is White Matter?:

In earlier Blogs we described how Vitamin B12 deficiency is associated with changes in 'white matter' in the brain and spinal cord. But what exactly is white matter?

Put very simply, it can be thought of as the brain's wiring.  But is there any evidence of changes in this wiring in patients with Alzheimer's Disease?


White Matter and Dementia:

White matter changes in patients with dementia were first described in 1986 (Ann.Neurol.1986;19:253-62).  Later, improvements in imaging techniques showed that these changes were actually quite common in patients with Alzheimer's Disease.

Moderate to severe white matter changes in the central part of the brain were found in as many as 70% of patients with the disease. They were also found in up to 80% of patients with Vascular Dementia (Arch.Neurol.2000;57:925-6).



The technical term for white matter changes seen on scans is 'leukoaraiosis.' Risk factors associated with leukoaraiosis are increasing age, and a history of stroke or hypertension.  The consensus view is that it is associated with disease of small blood vessels.

In a study of 195 cognitively impaired individuals, leukoaraiosis was also found to be associated with higher blood homocysteine levels.  Interestingly, leukoaraiosis was more frequent in patients with Alzheimer's Disease compared with other dementias including Parkinson’s Disease and Vascular Dementia (Ann.N.Y.Acad.Sci. 2000;903:497-500).


'..Correcting High Homocysteine Should Begin Early in Life':

The link between leukoaraiosis and high homocysteine has been confirmed in other studies in middle-aged men.  The researchers suggested that '..correcting high homocysteine should begin early in life if its deleterious effects on the brain are to be prevented' (Arch.Neurol.2004;1369-76).


In our next Blog Update we will look at the link between high homocysteine and brain shrinkage.

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