When Is a Conductive Hearing Loss Not a Conductive Hearing Loss? Causes of a Mismatch in Air-Bone Threshold Measurements or a “Pseudoconductive” Hearing Loss

The otolaryngologist is sometimes faced with a patient with an apparent conductive hearing loss on audiometric testing who appears to have normal and mobile middle ear structures on ear exploration. Some causes of these "pseudoconductive" hearing losses can be diagnosed without resorting to surgery. This article reviews several possible mechanisms for this condition with diagnostic procedures to distinguish etiologic diseases. Conditions discussed include poor audiometry, functional hearing losses, "third window" causes, obliterated round window, abnormal inner ear connection with the cerebrospinal fluid space, inner ear mechanical conductive hearing loss, and apparent inner ear loss owing to missed middle ear pathology.