What is the Endolymphatic Sac?

“Memorizing and regurgitating are not science. Real science is a constant investigation of the unknown.”
– Abhijit Naskar
Just when we think we have a handle on a structure and function of the body, we learn something entirely new. It’s this “constant investigation of the unknown” that has led scientists to now uncover the function of a small structure within the inner ear, the endolymphatic sac. While experts have long known about the endolymphatic sac and its existence within the inner ear until now little has been known about what it actually does.
That has all changed now thanks to the curiosity of two researchers at Harvard Medical School.
The endolymphatic sac of the inner ear
Deep within the ear, past the outer and middle ear, is what we know as the inner ear. This vital piece of the hearing puzzle is made up of the cochlea, the balance mechanism, the vestibular and the auditory nerve. Tucked within these structures, partially in bone, is the small endolymphatic sac.
Because of its size and difficult-to-reach location, the endolymphatic sac’s function has remained somewhat of a mystery. Experts hypothesized its role in fluid regulation and certain hearing health conditions such as Meniere’s Disease, but they were still uncertain. It was too small and too buried in bone to observe or study easily.
Curiosity wins the day
It was Ian Swinburne’s curiosity about the movement he saw in the endolymphatic sac that ultimately led to a breakthrough. The Harvard Medical School research fellow in systems biology along with his postdoctoral advisor Sean Megason, HMS associate professor of systems biology set out to learn more about the structure and its role in the complex world of the inner ear.
Working with leading microscopy laboratories, Swinburne and Megason spent several years creating a more complete view of the endolymphatic sac and how it functions. Their findings were published in June. The team confirmed that the endolymphatic sac functions as “a pressure-relief valve and is formed by a thin barrier of cellular projections that opens and closes to regulate the release of fluid from inside the inner ear.”
“Every once in a while, you hear about a house being destroyed by a water heater because its pressure release valve was defective,” Swinburne said. “It’s important to have these safety control systems in our organs as well.”
What this means for hearing health
What is most exciting about Swinburne and Megason’s research is what their findings could mean for those affected by certain conditions of the inner ear.  Vertigo, Meniere’s disease, even tinnitus and hearing loss could be treated more effectively in the future thanks to this new understanding of a once rather mysterious structure of the inner ear.
While there is still much to learn about the endolymphatic sac and its role in hearing health and balance, this detailed new view of its function is a leap towards better hearing for many.
If you have concerns about your hearing, call our office to schedule a hearing evaluation today. Early treatment can make all the difference in healthy hearing!


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