Ischemic demyelination.

White matter lesions representing ischemic demyelination have evolved in terms of our understanding of their pathogenesis and potential clinical significance. Low density lesions on CT brain scan, most commonly seen in the periventricular region, also frequently seen in the centrum semiovale, have been termed 'leukoaraiosis'. In the past years, it was not uncommon at all to hear the term 'Binswanger's disease' used in an attempt to define the neurological sequelae of such lesions. Further refinement came with the advent of magnetic resonance imaging (MRI) brain scan which is particularly sensitive to such white matter areas of increased signal intensity, which tend to be seen particularly well on T2-weighted and fluid attenuation inversion recovery (FLAIR) scans. The major challenge has been to correlate the clinical attributes with such relatively frequent findings in the elderly population. Recent studies have looked at lesion load in a fashion analogous to that seen with multiple sclerosis. A particularly relevant clinical model for white matter disease is cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) which combines the potential components of small vessel disease, resulting in progressive neurological deficit, with a common association with migraine which can also be associated with white matter lesions. However, the most common pathogenic factor associated with the microangiopathy, which appears to be at the heart of ischemic demyelination, continues to be hypertension. How well we are able to tie in the various pathological mechanisms associated with this end organ damage of the brain will determine how well we can arrive at effective interventions for a common contributor to neurological deficits in the elderly.