[Otosclerosis and Van der Hoeven's syndrome: a contribution]

Effect of stapes demineralisation on the development of cochlear otosclerosis

Objective

The involvement of the inner ear in otosclerosis may lead to the development of cochlear otosclerosis. The aim of this study was to analyse changes in the chemical composition and microstructure of the stapes in the course of otosclerosis compared to healthy stapes.

Materials and methods

This analysis included 31 patients with otosclerosis and 9 patients without otosclerosis. Microanalytical and diffraction techniques were used to assess the elemental distribution and orientation topography of the stapes.

Results

The concentration of Ca2+ in the study group was significantly lower in the area of the anterior crus of the stapes than in the posterior crus. A reduction in the Ca2+/P3+ ratio in the anterior crus was associated with deteriorated bone conduction and tinnitus. Degradation of the stapes microstructure in the area of otosclerotic lesions was observed with scanning electron microscopy.

Conclusions

Bone remodelling is most significant at the closest location to typical otosclerotic lesions with hydroxyapatite porosity and scale-like bone formation according to scanning electron microscopy. There is a relationship between the disturbance of calcium metabolism and the development of clinical symptoms of cochlear otosclerosis.

Hearing loss in osteogenesis imperfecta: characteristics and treatment considerations

Osteogenesis imperfecta (OI) is the most common heritable disorder of connective tissue. It is associated with fractures following relatively minor injury, blue sclerae, dentinogenesis imperfecta, increased joint mobility, short stature, and hearing loss. Structures in the otic capsule and inner ear share in the histologic features common to other skeletal tissues. OI is due to mutations involving several genes, the most commonly involved are the COL1A1 or COL1A2 genes which are responsible for the synthesis of the proalpha-1 and proalpha-2 polypeptide chains that form the type I collagen triple helix. A genotype/phenotype relationship to hearing loss has not been established in OI. Hearing loss is commonly found in OI with prevalence rates ranging from 50 to 92% in some studies. Hearing loss in OI may be conductive, mixed, or sensorineural and is more common by the second or third decade. Treatment options such as hearing aids, stapes surgery, and cochlear implants are discussed.