Isolated congenital round window absence.

Absence of the round window as a congenital defect is a rare entity that causes a conductive hearing loss. To the best of our knowledge, isolated and nonsyndromal round window absence has only been reported 3 times; the diagnoses were made during surgery. We are reporting on another case that was diagnosed before operation by virtual endoscopy of the middle ear during a high-resolution computed tomography scan. Although this new technique requires further validation, it may be an alternative to surgery as a means of confirming this rare diagnosis.