White matter hyperintensities (WMH)

White matter hyperintensities (WMH) are patches that light up abnormally bright on certain brain MRI scans (T2-weighted and FLAIR), within the brain's white matter. They are not one single thing. They reflect a mix of lost myelin, lost axons, scarring (gliosis), and small-vessel oxygen starvation. They become much more common with age. Roughly 10 to 20% of people in their 60s have them, and most people over 80 do. Their volume is strongly tied to high blood pressure, diabetes, and smoking, all of which you can change. WMH predict cognitive decline (especially in processing speed and executive function), as well as future dementia, stroke, and death. Large or fast-growing merged patches carry more weight than small dot-like ones. They are a key imaging sign of cerebral small-vessel disease, and of vascular contributions to cognitive impairment and dementia (VCID).

Last reviewed: June 22, 2026

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