New aspects in the clinical diagnosis of otosclerosis using laser Doppler vibrometry.

HYPOTHESIS: Laser Doppler vibrometry (LDV) applied to umbo motion measurement in healthy and otosclerotic ears shows statistically tested differences.

BACKGROUND

The LDV is a research tool that measures middle ear function by registering sound-induced tympanic membrane velocity. Its possible application in the diagnosis of different middle ear disorders, especially otosclerosis, is currently being evaluated. Established diagnosis can identify various ossicular chain pathologies in most cases but is still sometimes contradicted by the findings of surgical middle ear exploration.

METHODS

We used a fractionally modified LDV setting as previously reported to evaluate 150 normal-hearing ears and 49 ears with conductive hearing loss. In a first step, the impact of age variation on the umbo transfer function was investigated by dividing the normal-hearing population into 3 age groups. In a second step, the control group was compared with patients with conductive hearing loss; certain patterns in the umbo transfer function were especially investigated by discriminant analysis.

RESULTS

Mean magnitude of the oldest group was found to be significantly higher than the other 2 groups, but it was not possible to diagnostically classify the 3 groups. Discriminant analysis revealed the linear term of a cubic polynom to significantly best describe the umbo transfer function in normal ears (p < 0.0005; partial eta = 0.866) and in otosclerotic ears (p < 0.0005; partial eta = 0.799). Separating otosclerotic ear from normal-hearing ear evidence suggests a sensitivity of 82% and specificity of 92%.

CONCLUSION

Evaluation of LDV magnitude curve patterns gives helpful information in the diagnosis of otosclerosis but does not suffice as a single diagnostic tool.