Thursday, October 27, 2011

Brain White Matter Changes Increase Dementia Risk

Diffuse White Matter Hyperintentsity in CADASIL
Approximately a year ago, I reviewed some of the growing evidence of the clinical significance of brain white matter intensities or lesions.  Magnetic resonance imaging identifies these types of lesions but their significance had been unknown.


The review noted that white matter hyperintensities appear to increase future risk for several disorders including stroke and dementia.  Additionally, these lesions have increase mortality rates in some follow up studies.


Now an additional study has examined the effect of these lesions on dementia.  Inaba and colleagues examined the progress of cognitive decline in a group of elderly individuals participating in the Honolulu-Asia aging study.


The study followed 267 men between the ages of 74 and 95.  At baseline, brain MRI scans were rated for the presence and grade level of white matter lesions. A cognitive function test (Cognitive Abilities Screening Instrument) was obtained at baseline and five years later repeated.  Significant cognitive decline was defined as a drop of 12 points or more over the five year period.


Subjectives with significant white matter lesions had higher rates of cognitive decline (34.4%) compared to the control group without these lesions (22.4%).


Men with the lesions were more likely at baseline to have a diagnosis of hypertension and show evidence of a small infarct (stroke) on MRI.  They did not differ on rates of depression or smoking history.  Baseline differences on potential confounding variables were controlled in this study using multivar


The effect of white matter lesions on cognitive decline appeared to be stronger in those without the gene known to be associated with Alzheimer's disease risk (ApoE).


The authors propose that white matter lesions may reflect damage to brain connectivity tracts.  This could result in slowing speed of neural transmission.  This may be the mechanism for neuropsychological studies linking white matter lesions to reduced cognitive processing speed, attention and executive function.


Further research is needed to identify potential preventive interventions to reduce the risk of these lesions.  


MRI brain image showing white matter hyperintensities in a frontal to occipital distribution from a patient with CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy).  From the Wikipedia Commons file authored by Bohlega S, Al Shubili A, Edris A, Alreshaid A, Alkhairallah T, AlSous MW, Farah S, Abu-Amero KK.


Inaba M, White L, Bell C, Chen R, Petrovitch H, Launer L, Abbott RD, Ross GW, & Masaki K (2011). White matter lesions on brain magnetic resonance imaging scan and 5-year cognitive decline: the Honolulu-Asia aging study. Journal of the American Geriatrics Society, 59 (8), 1484-9 PMID: 21718274

1 comment:

  1. I think this is it.
    Leukoaraiosis or periventricular white matter disease is a term for changes in the cerebral white matter that can be detected with high frequency by CT and MRI in aged individuals.

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