Research Signal – Source date 2025-12-11
Dementia research often focuses on what accumulates in the brain and how that buildup might be reduced. A review published on December 11, 2025, considers a related question: could difficulty draining blood from the brain also interfere with the movement of fluids that help clear waste?
The idea is biologically plausible, and studies reviewed by the authors link cognitive impairment with measures of venous structure, blood-flow pulsatility and fluid movement around brain tissue. But those observations come from different populations and measure different things. They do not establish that impaired venous outflow causes dementia, or show that treating it changes dementia in older adults.
How brain fluids and veins meet
The brain’s glymphatic system is a proposed route for exchanging cerebrospinal fluid (CSF) with interstitial fluid (ISF), the fluid between brain cells. In the account summarized by the review, CSF moves along spaces around arteries and exchanges with ISF in brain tissue. This fluid movement can carry substances such as β-amyloid and tau toward spaces around veins, then onward toward meningeal lymphatic vessels and lymph nodes in the neck.
The glymphatic system and the veins are related, but they are not the same drainage system. The review describes venous spaces as part of the surrounding structure used in the exchange and movement of fluids; it does not describe the glymphatic system as draining directly into veins.
Arterial pulsations help move CSF, while pressure in the veins affects the conditions under which fluid can leave the brain. If venous pressure rises, it may reduce the pressure difference that helps drive fluid movement. The proposed consequence is less efficient clearance through perivascular spaces. This is a mechanism the review brings together from existing work, not a dementia treatment result or proof that this sequence occurs in every affected person.
A proposed route from congestion to cognitive difficulty
Venous outflow problems could matter through more than waste clearance. The review describes how aging-related changes in small cerebral veins, including thickening and twisting, may increase resistance to blood leaving the brain. The resulting congestion could reduce perfusion pressure and contribute to chronic underperfusion.
White matter near the brain’s ventricles may be especially vulnerable. The small veins serving this region have limited collateral support, according to the review. If drainage is impaired, fluid balance and waste removal may also be affected. The authors connect these conditions with tissue changes including loss of axons, damage to myelin-producing cells, thinning of myelin and activation of glial cells. Because white matter helps connect brain regions, injury there could disrupt communication and affect functions such as executive skills and processing speed.
The review also outlines a possible link with the blood-brain barrier. Reduced perfusion may promote oxidative stress and processes that weaken the barrier’s structural components. If that barrier becomes more permeable, immune cells and plasma proteins can enter brain tissue and contribute to inflammation and white matter damage.
These steps offer a way to think about how venous problems might contribute to cognitive decline. They are not a demonstrated, complete chain from venous narrowing to dementia. Aging, vascular changes and cognitive disease can overlap, and the evidence summarized here does not show which change comes first.
What the measurements can—and cannot—tell us
Some studies reviewed by the authors compare the size or cross-sectional area of cerebral veins in people with Alzheimer disease or mild cognitive impairment (MCI) and cognitively healthy controls. A smaller measured area is evidence of a structural difference in those groups. It can support a question about drainage, but does not by itself establish impaired flow or show that a venous change caused cognitive symptoms.
Other studies examine venous pulsatility: variation in blood-flow velocity over time. The review describes higher pulsatility-index values in several major venous sinuses among people with Alzheimer disease or MCI than among controls. The proposed interpretation is that stronger arterial pulsations may be transmitted into the venous system when the brain’s usual cushioning dynamics are altered. That interpretation is plausible, but a pulsatility measure is not a direct measure of waste clearance or a diagnosis of the cause of dementia.
The review also discusses the ALPS index, an imaging measure used as a proxy for perivascular fluid movement. Lower values have been reported in Alzheimer disease and associated with cognitive function. This adds an observation about fluid movement around vessels. It does not show that raised venous pressure caused the difference: the relationship between the measure, venous function and cognitive disease remains open.
The different measures make the overall picture more interesting, but they cannot simply be treated as interchangeable confirmation. Vein size, pulsatility and a proxy for perivascular movement capture distinct features. Their associations do not determine whether venous changes precede cognitive impairment, follow it, or share other causes with it.
Intracranial hypertension offers a clue, with limits
Idiopathic intracranial hypertension (IIH) is a condition involving elevated pressure inside the skull. The review describes venous sinus narrowing in most patients with IIH and a proposed feedback loop: pressure can compress a susceptible sinus, narrowing it further and worsening congestion. This relationship makes IIH a useful clinical setting in which venous narrowing, pressure and symptoms can occur together.
Cognitive difficulties have also been described in IIH. Studies summarized in the review report differences in areas such as attention, memory, learning and processing speed. One study found improvement in sustained attention as intracranial pressure was reduced. That observation suggests that pressure-related cognitive symptoms can be responsive in this particular clinical context.
IIH is not a stand-in for dementia in older adults. It is a different condition, and the evidence described here concerns people with intracranial hypertension rather than a trial of venous treatment for Alzheimer disease or other dementias. It helps motivate the question of whether venous pressure can affect cognition; it does not answer whether venous insufficiency drives age-related dementia.
What procedure reports actually show
The review describes reports of cognitive or mental well-being improvement after venous sinus stenting or procedures involving jugular-vein narrowing. The patients were selected for venous-pressure conditions, including IIH or a primary venous pressure gradient. Some reports recorded patients’ descriptions of symptoms such as “brain fog”; others compared self-reported well-being or related outcomes after intervention.
For example, one report involving patients with Ehlers-Danlos syndrome described improvement or resolution of headaches and cognitive dysfunction in 77% of patients after stenting. A comparison of women with IIH who received stenting or medical treatment found better reported outcomes in several areas of well-being and daily functioning in the stenting group. A separate retrospective report in patients with venopathic intracranial hypertension found improvement in self-reported cognition and several other symptoms after stenting.
These findings concern symptoms and reported well-being in particular groups. They are reasons to investigate how treating venous pressure might help some patients with those conditions. They do not establish that stenting slows dementia progression or improves cognition in older people with dementia. The review’s treatment discussion therefore provides a rationale for research, not a treatment result that can be transferred to a different population.
What would identify a contributing venous problem
The central question is whether venous dysfunction is a contributor to cognitive decline in some older adults, or a change that accompanies other processes. Answering it will require connecting the location and functional significance of venous abnormalities with clinical context and cognitive outcomes in older patients.
A narrowing or altered flow measure alone cannot identify who might benefit. Researchers would need to determine how those findings relate to fluid movement and cognition, and whether intervening on a defined venous problem changes outcomes in the people who have it. The review calls for investigation of venous findings beyond IIH and of the potential role of stenting in older adults with cognitive decline.
What a treatable drainage problem could mean for dementia care
If future studies show that a specific, treatable venous problem contributes to cognitive decline in a defined group of older adults, clinicians could eventually have another way to identify and help some patients. That possibility depends on establishing the connection between venous findings and cognition, then showing that intervention improves meaningful outcomes in that population. The 2025 review makes the case for investigating that path; it does not establish that the path is already a dementia treatment.
Key Sources
- Primary source: Cerebral Venous Insufficiency as a Contributing Factor in Dementia: An Emerging Hypothesis.
DOI or Journal Page · Review or Meta-Analysis · 2025-12-11
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