A Case of Transcanal Endoscopic Ear Surgery for Otosclerosis with a Malleus Bar

A malleus bar is a rare congenital ossicular anomaly characterized by a bony bridge connecting the bony annulus to the manubrium of the malleus, causing conductive hearing loss. It was first described by Nomura et al in 1988. While hearing improvement is achieved in most cases after removal of the bony bridge, coexistence of a malleus bar and otosclerosis has not been reported to date. A 46-year-old woman presented to us with progressive right-sided hearing loss and long-standing left-sided deafness since childhood. Otoscopic examination revealed no abnormalities on either side. Pure-tone audiometry demonstrated bilateral conductive hearing loss with absent stapedial reflexes. Temporal bone CT revealed a double ring sign in both cochleae and a demineralized focus at the left fissula ante fenestram, suggestive of bilateral otosclerosis. A faint bony structure was suspected between the manubrium and posterior canal wall on the right side. Surgery was first performed on the left side with poorer hearing via a transcanal endoscopic approach. A bony bridge connecting the malleus neck and posterior canal wall (malleus bar) was identified and drilled off. Stapes fixation was also observed, and stapedotomy was performed. Postoperatively, the average air conduction improved, but bone conduction worsened at 1 kHz. One year later, a conventional stapedotomy was successfully performed on the contralateral ear, which showed typical otosclerosis without a malleus bar. This is the first reported case of otosclerosis associated with a malleus bar. Given that the preoperative CT failed to allow clear visualization of the bony bridge, intraoperative findings remain crucial for diagnosis and surgical planning. In cases with multiple ossicular fixations, surgeons should consider that stapes fixation may be less severe than estimated from the air–bone gap, and intraoperative flexibility in surgical strategy is essential.