Emerging Concepts of Hearing Loss in Paget's Disease of Bone

Hearing loss has been recognized as a clinical feature of Paget’s disease of bone since Sir James Paget’s first case report (1). Involvement of the skull is commonly associated with involvement of the temporal bones and with hearing loss in Paget’s disease (2). An older concept that hearing loss in Paget’s disease is due to multiple mechanisms is giving way to a newer concept that there is a general mechanism causing hearing loss in most cases (3). Clinical and audiometric studies of hearing loss in Paget’s disease have described high-frequency sensorineural hearing loss and a low-frequency air–bone gap in most cases (4). (An air–bone gap indicates that auditory thresholds when measured by bone conduction are better than those predicted by air conduction thresholds.) An air–bone gap is usually interpreted as indicating a conductive type of deafness. Hearing levels have been shown to progress more rapidly in untreated Paget’s disease than in uncomplicated presbycusis (5). Histologic studies in the 1960s and 1970s showed a variety of derangements, including compression and stretching of the auditory nerve, microfractures of the otic capsule, loss of auditory hair cells and ganglion cells, invasion of labyrinthine spaces, and envelopment of ossicles by pagetic bone (4,6,7). More recently, histopathologic studies have also shown atrophy of the spiral ligament and endolymphatic hydrops (8). The presence of toxic cytokines has been shown in otosclerosis and suggested in Paget’s disease. Most of these data consist of histopathologic reports of advanced cases. On the other hand, the prominent histopathologist of the temporal bone, Harold F. Schuknecht, had long held the view that such dramatic findings were not the rule. He analyzed the largest group of histopathologic cases of Paget’s disease of the temporal bone to date in 1990 (9). Using a technique of graphic analysis that compared hearing levels in the range of the speech frequencies versus the loss of auditory hair cells and ganglion cells that carry the neural place code for each of those tones, he could not demonstrate any systematic relationships. Aside from the presence of pagetic bone, the specimens were typical for the age of the subjects. There were no findings that would explain the air-bone gap, such as fixation or disruption of the auditory ossicles.