Round-window anatomical considerations in intratympanic drug therapy for inner-ear diseases.

Our aim was to elucidate the importance of anatomical aspects in planning local therapies for inner-ear diseases. The study undertakes the anatomical evaluation, from a surgical-approach perspective, of the relationship between the false and true round-window membranes. As our design, we chose a human temporal bone dissection study, for which we used 20 fresh temporal bones. After an exploratory tympanotomy and atticotomy, we drilled the anterosuperior (promontory) edge of the round-window niche until the true round-window membrane was completely exposed. We registered the presence or absence and the extent of the false round-window membranes on the round-window niche. We found false round-window membranes obstructing the round-window niche partially or completely in five temporal bones (25%). Complete obstruction was present in one temporal bone (5%). We found mucoperiosteal folds obstructing the round-window niche partially or completely in a significant proportion of the ears. These anatomical particularities could account, at least partially, for the great variability of the results of intratympanic therapies for inner-ear diseases.