A diagnostic pitfall: Advanced labyrinthitis ossificans simulating congenital inner ear malformation on CT and MRI.

Labyrinthitis ossificans (LO) is a rare pathological ossification of the membranous labyrinth, typically arising after inflammatory or infectious insults to the inner ear. We present a case of a 65-year-old male with type 2 diabetes presenting with progressive unilateral sensorineural hearing loss and a history of recurrent childhood ear infections treated with repeated lavages. Imaging revealed advanced ossification of the right cochlea, vestibule, and semicircular canals, despite no history of meningitis or trauma. Magnetic resonance imaging (MRI) revealed near-complete loss of the normal fluid signal in the affected labyrinth, while high-resolution CT confirmed extensive bony obliteration with a small residual segment of the basal turn spared. The absence of vestibular symptoms despite semicircular canal ossification highlights the variable clinical presentation of LO. This case illustrates how advanced LO can closely mimic congenital inner ear malformations on imaging, making accurate diagnosis particularly challenging. Differential diagnoses such as cochlear otosclerosis, temporal bone fractures, and autoimmune inner ear disease must be carefully excluded based on clinical and radiological features. Treatment options depend on the ossification stage; while cochlear implantation remains feasible in early or partial ossification, advanced cases may require alternative rehabilitation strategies. Early diagnosis is crucial for optimizing hearing outcomes. This report emphasizes the importance of combining clinical history, audiometry, and multimodal imaging in the diagnosis and management of LO.