Imagine exploring a vast forest, where each area has its own unique ecosystem. In the aging brain, periventricular white matter hyperintensities (PWMHs) and deep white matter hyperintensities (DWMHs) are like two different ecosystems, each with its own distinct mechanisms. PWMHs appear to be primarily caused by damage to veins due to dysfunction in the glymphatic pathway, which is responsible for waste clearance in the brain. On the other hand, DWMHs can be influenced by both ischemia-hypoperfusion (reduced blood flow) and dysfunction in the glymphatic pathway. This fascinating study examined 152 old participants and revealed intriguing findings. The researchers discovered that age and a history of hypertension were linked to larger volumes of both PWMHs and DWMHs. Additionally, reduced glymphatic function and lower cerebral blood flow were independent risk factors for larger DWMH volumes, whereas lower glymphatic function alone was associated with larger PWMH volumes. These results shed light on the complex ways in which white matter hyperintensities form and progress in aging brains. For more information on this exciting research, dive into the full article!

ObjectiveAlthough multiple pieces of evidence have suggested that there are different mechanisms in periventricular white matter hyperintensities (PWMHs) and deep white matter hyperintensities (DWMHs), the exact mechanism remains uncertain.MethodsWe reviewed clinical and imaging data of old participants from a local She Ethnic group. We assessed the cerebral blood flow of white matter (WM-CBF) on arterial spin-labeling, deep medullary veins (DMVs) visual score on susceptibility-weighted imaging, and index for diffusion tensor image analysis along the perivascular space (ALPS index), indicating glymphatic function on diffusion tensor imaging. Furthermore, we investigated their relationships with volumes of PWMHs and DWMHs.ResultsA total of 152 subjects were included, with an average age of 63 ± 8 years old. We found that higher age and history of hypertension were independently related to higher volumes of both PWMHs and DWMHs (all p < 0.05). Lower ALPS index was independently associated with higher PWMHs volumes (β = 0.305, p < 0.001), and this relationship was accounted for by the indirect pathway via DMVs score (β = 0.176, p = 0.017). Both lower ALPS index and WM-CBF were independent risk factors for higher DWMHs volumes (β = −0.146, p = 0.041; β = −0.147, p = 0.036).ConclusionsOur study indicated that there were different mechanisms in PWMHs and DWMHs. PWMHs were mainly attributed to the damage of veins due to the dysfunction of the glymphatic pathway, while DWMHs could be affected by both ischemia-hypoperfusion and dysfunction of the glymphatic pathway.Advances in knowledgeThe relationship between glymphatic dysfunction and PWMHs might be accounted for by the indirect pathway via venous abnormalities, a glymphatic dysfunction, and lower CBF in white matter were independent risk factors for DWMHs.

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