Endolymph pressure in Menière's disease.

During the streptomycin perfusion/shunt of the lateral semicircular duct operation for Meniere's disease, the lateral semicircular duct is exposed by removal of the bone of the lateral semicircular canal. Before perfusion with streptomycin and creation of a shunt in the lateral semicircular duct, the pressure in the lateral semicircular duct is measured while electrocochleography is being recorded. In most ears with Meniere's disease, the pressure necessary to indent the lateral semicircular duct is 2 to 3 mm of water. The pressure is more in those ears with a large negative summating potential than in those with a normal negative summating potential. The pressure is less after the shunt in the lateral semicircular duct is created and the negative summating potential returns to normal. In some ears with the classic picture of Meniere's disease, the endolymph pressure is normal and there is a normal negative summating potential. Presumably, one should not create a shunt in the lateral semicircular duct in ears with normal pressure.