OIL-ON-WATER - PROPOSED METHOD FOR INTRAOPERATIVE IDENTIFICATION OF PERILYMPHATIC FISTULA

The intraoperative diagnosis of a perilymphatic fistula is usually sub jective and controversial. Unless there is profuse gushing of fluid, t here is no reliable, objective, intraoperative indicator of a perilymp hatic fistula. The authors suggest a technique for the real-time deter mination of the existence and location of a perilymphatic fistula: vis ualization of clear perilymphatic fluid beneath a layer of mineral oil . Mineral oil is transparent to visible light, hydrophobic, and lighte r than perilymphatic fluid. The oil traps the aqueous fluid, and tends to keep it contained in a droplet. With standard otomicroscopic viewi ng, a droplet of less than 1 mu L of fluid is readily visible through the oil. In vitro temporal bone studies showing the utility and object ivity of identifying the aqueous fluid in the mesotympanum are reporte d. Mineral oil floats on saline and is readily removed with suction-ir rigation techniques. The authors consider the oil-on-water technique t o increase the resolution of identifying minute aqueous droplets and r ecommend in vivo study in patients.