IBS and KAIST researchers identified ‘arachnoid fenestrations’ — microscopic openings through which cerebrospinal fluid drains from the brain — publishing the discovery in the journal Cell
🎧 Post Summary
📌 Summary
South Korean scientists have discovered, for the first time, the hidden pathway through which cerebrospinal fluid clears waste out of the brain — a set of microscopic openings called ‘arachnoid fenestrations.’ The pathway narrows with age, but delivering a specific gene into the nasal cavity of aged mice reopened it and restored drainage to youthful levels. Published in the journal Cell, the study points to a non-invasive, nasal-spray-based strategy for treating dementia.
It is no longer unusual to hear of memory slipping with age, or of more family members and friends being diagnosed with dementia. One of the key culprits is waste that builds up in the brain — neurotoxic proteins such as amyloid beta. Yet exactly how this waste exits the brain remained one of science’s oldest unsolved puzzles for nearly 250 years. Korean researchers have now filled in that final piece, opening a potential new path to preventing and treating dementia with a drug delivered through the nose.
① The Final Piece of a 250-Year Puzzle
The brain constantly generates waste as it operates, and clears it out through the cerebrospinal fluid (CSF) — the brain’s own ‘cleaning’ system. When this clearance process fails, toxic proteins such as amyloid beta accumulate and can lead to dementia and other neurodegenerative diseases.
The team led by Director Gou Young Koh of the IBS Center for Vascular Research (also a distinguished professor at KAIST’s Graduate School of Medical Science and Engineering) had already shown in Nature papers in 2019 and 2024 that CSF drains through meningeal lymphatics at the base of the brain and nasopharyngeal lymphatics into the neck lymph nodes. In 2025, the team also identified an additional drainage route through lymphatic vessels beneath the facial skin around the eyes and nose, and found that gentle mechanical stimulation could promote drainage.
But exactly how CSF first breaks through the arachnoid membrane — the tough barrier that tightly wraps the brain — had remained unknown. This was the final unresolved link in a chain of discovery that began roughly 250 years ago, when meningeal lymphatic vessels were first identified. The team’s new study has now closed that gap.
② What Are ‘Arachnoid Fenestrations’?
Using fluorescent tracers and precise 3D reconstruction of CSF flow in mice, along with direct scanning electron microscope imaging, the team identified microscopic pores in the arachnoid membrane near the olfactory bulb. They named this structure ‘arachnoid fenestrations.’
CSF exits the arachnoid membrane through these pores, then passes through the olfactory meningeal lymphatics and nasal lymphatic vessels before finally reaching the cervical (neck) lymph nodes. For the first time, the entire route — from the very start of brain-waste drainage to its endpoint — has been mapped as one continuous pathway.
③ Why Aging Makes the Brain ‘Dirtier’
Analyzing aged mice, the team found that arachnoid fenestrations narrow and the surrounding meningeal lymphatic vessels decrease in number. The cribriform plate — the passage through which lymphatic vessels and the olfactory nerve travel — also narrows, sharply reducing overall CSF drainage.
This offers a compelling explanation for why the brain’s cleaning function weakens with age, allowing toxic proteins to accumulate and raising the risk of dementia.
④ Making an Aged Brain Young Again With a Nasal Gene Therapy? The Animal Study Results
The researchers administered VEGF-C, a gene that promotes lymphatic vessel growth, to the nasal mucosa of aged mice. The surrounding lymphatic vessels regrew, the narrowed drainage pathway widened again, and CSF drainage function was restored to levels seen in young mice.
This suggests that a non-invasive, nasally administered treatment alone could revive the brain’s waste-clearing function — a finding that may point toward an entirely new strategy for developing dementia treatments.
⑤ Could This Work in Humans? Primate Confirmation and Next Steps
Dr. Sunju Hong, the researcher who led the study, said the same arachnoid fenestration structure was confirmed in primates as well — a key clue suggesting that humans may have a similar brain-cleaning pathway. The team plans to extend the research to human tissue and to develop treatment strategies applicable to a range of neurodegenerative diseases.
The study was led by IBS and KAIST, in international collaboration with the University of Helsinki in Finland, the University of California, San Francisco (UCSF) in the United States, and the Korea Research Institute of Bioscience and Biotechnology (KRIBB).
📌 Things Worth Keeping in Mind
- This research is based on animal (mouse) experiments; in primates, only the underlying structure has been confirmed so far. Human clinical trials have not yet begun.
- Despite headlines about a ‘nasal spray for dementia,’ turning this into an actual approved treatment will require extensive further work to verify safety and efficacy.
- This is a basic-science breakthrough in understanding a root cause of dementia — it does not replace existing dementia treatments or imply an immediate therapeutic effect.
- The safety of the gene-delivery method and whether it truly works the same way in humans remain open questions for future research to answer.
A 250-year-old mystery about how the brain clears its own waste has finally found a thread of an answer, thanks to Korean researchers. There is still a long road ahead before this reaches human patients, but the very idea that a nasal spray alone could help clean the brain shows how much dementia research could change going forward. Continued progress in human tissue studies and eventual clinical trials will be worth watching closely.
References
- Herald Corp (Herald Business) — “Korean researchers discover brain-waste drainage pathway, offering clues for dementia treatment” (biz.heraldcorp.com)
- Science Times — “IBS Center for Vascular Research discovers ‘arachnoid fenestrations’ through which CSF crosses the meninges” (sciencetimes.co.kr)
- Hidoc — “Korean researchers discover first gateway of brain-waste drainage — new hope for overcoming dementia?” (news.hidoc.co.kr)
- BRIC — “Discovery of the ‘first gateway’ for brain-waste drainage opens new chapter in brain-disease research” (ibric.org)
- Asia Economy — “Brain-waste drainage outlet found — a new path for dementia treatment” (asiae.co.kr)
- Chungcheong Today — “IBS identifies ‘arachnoid fenestrations,’ the first gateway for brain-waste drainage, for the first time in the world” (via Daum News)
- KBS News — “[Issue] A ‘Spray’ for the Nose to Eradicate Brain Waste — Is Korea Becoming a Pioneer in Dementia Treatment?” (youtube.com)