CASE 13203 Published on 02.12.2015

CT contribution in otosclerosis



Case Type

Clinical Cases


Bouachra S, Laamrani FZ, Amal R, En-nouali H, Boumdin H, Amil T

Hôpital militaire d'instruction Mohamed V
3, Rue Hassan 2 Rabat, Morocco;

45 years, female

Area of Interest Neuroradiology brain ; Imaging Technique CT
Clinical History
A 45-year-old male patient presented with no significant medical history, a progressive bilateral hearing loss and no other associated signs. Otoscopic examination showed no abnormalities and audiometry revealed bilateral transmissional surdity, combined with abolition of stapedial reflex.
Imaging Findings
A CT objectified thickening of the stapes footplate measuring 0.8 mm, associated to a bilateral hypodense demineralised plaque of the oval windows and around the cochlea arriving up in front of the auditory meatus and the round window (Figure 1-4). The ossicular chain was morphologically normal (Figure 5), with no narrowing of the oval window or prolapse of the promontory or facial canal.
Otosclerosis is a common primitive osteodystrophy of labyrinthine bone developing from residual cartilaginous islets of the otic capsule. It is often a genetic autosomal dominant disease, with an incidence of approximately 0.1% in Caucasian individuals and the disease is often bilateral and asymmetrical [1].
It manifests clinically by a usually bilateral progressive hearing loss, frequently associated with tinnitus. The otoscopic examination shows a normal eardrum with absence of associated middle ear pathology, and audiometry often shows a transmissional hearing loss mostly, sometimes combined with elimination of acoustic reflex [1-3].
CT is the imaging reference in the exploration of otosclerosis. It can confirm the diagnosis with a sensitivity of 95% and a specificity of 99.5%, and also shows the extent of lesions, and allows prognosis and specification of the anatomical conditions of the surgery [1, 4, 5].
The technique requires a helical acquisition without contrast injection. The main axial plane should be parallel to the lateral semicircular canal spotted from the sagittal and coronal sections. The coronal plane is useful in assessing the importance of the demineralised plaques and to analyze the relationship between the second portion of the facial canal and the underlying oval window [5, 6].
The diagnosis relies on the detection of localized hypodensities of the oval window in contact with the implantation of the anterior branch of the stapes footplate but also in other localizations including the anterior labyrinthine layer, and around the cochlea, in the advanced forms resulting in a pseudo 4th round of cochlea [1, 5, 7].
The treatment of osteosclerosis is essentially surgical (stapedotomy is often preferred to platinectomy) [8].
CT is routinely performed for any transmissional hearing loss and before surgery to avoid operational surprises. It is useful for a positive diagnosis and staging.
Differential Diagnosis List
Symmetrical bilateral otosclerosis
Dehiscence semi upper circular canal
Malformation of the ossicular chain
Final Diagnosis
Symmetrical bilateral otosclerosis
Case information
DOI: 10.1594/EURORAD/CASE.13203
ISSN: 1563-4086