The cause of Ménière's disease is unknown, but it may be related to a fluid imbalance in the inner ear. This fluid (endolymph) is contained in a part of the inner ear called the endolymphatic sac.
An endolymphatic shunt is a small tube inserted in the endolymphatic sac to allow excess fluid (endolymph) to drain. By removing the excess fluid, pressure does not build up and vertigo does not occur.
The effectiveness of this procedure has become controversial, so it is no longer done as frequently as in the past.
WebMD Medical Reference from Healthwise