Sequential motion of the ossicular chain measured by laser Doppler vibrometry

The human middle ear in motion: 3D visualization and quantification using dynamic synchrotron-based X-ray imaging

The characterization of the vibrations of the middle ear ossicles during sound transmission is a focal point in clinical research. However, the small size of the structures, their micrometer-scale movement, and the deep-seated position of the middle ear within the temporal bone make these types of measurements extremely challenging. In this work, dynamic synchrotron-based X-ray phase-contrast microtomography is used on acoustically stimulated intact human ears, allowing for the three-dimensional visualization of entire human eardrums and ossicular chains in motion. A post-gating algorithm is used to temporally resolve the fast micromotions at 128 Hz, coupled with a high-throughput pipeline to process the large tomographic datasets. Seven ex-vivo fresh-frozen human temporal bones in healthy conditions are studied, and the rigid body motions of the ossicles are quantitatively delineated. Clinically relevant regions of the ossicular chain are tracked in 3D, and the amplitudes of their displacement are computed for two acoustic stimuli.

In Vivo Measurement of Ear Ossicle and Bony Wall Vibration by Sound Stimulation of Cartilage Conduction

The cartilage-conduction pathway was recently proposed as a third auditory pathway; however, middle-ear vibrations have not yet been investigated in vivo. We aimed to measure the ossicles and bone vibration upon cartilage-conduction stimulation with a non-contact laser Doppler vibrometer. We recruited adult patients with normal ear structures who underwent cochlear implant surgery at our hospital between April 2020 and December 2022. For sound input, a cartilage-conduction transducer, custom-made by RION Corporation (Tokyo, Japan), was fixed to the surface of the tragus and connected to an audiometer to regulate the output. A posterior tympanotomy was performed and a laser beam was directed through the cavity to measure the vibration of the ossicles, cochlear promontory, and posterior wall of the external auditory canal. Five participants (three men, mean age: 56.4 years) were included. The mean hearing loss on the operative side was 96.3 dB HL in one patient, and that of the other patients was off-scale. The vibrations were measured at a sound input of 1 kHz and 60 dB. We observed vibrations of all three structures, demonstrating the existence of cartilage-conduction pathways in vivo. These results may help uncover the mechanisms of the cartilage-conduction pathway in the future.

Handheld laser-fiber vibrometry probe for assessing auditory ossicles displacement

SIGNIFICANCE

Measurements of auditory ossicles displacement are commonly carried out by means of laser-Doppler vibrometry (LDV), which is considered to be a gold standard. The limitation of the LDV method, especially for in vivo measurements, is the necessity to expose an object in a straight line to a laser beam operating from a distance. An alternative to this approach is the use of a handheld laser-fiber vibrometry probe (HLFVP) with a curved tip.

AIM

We evaluate the feasibility of an HLFVP with a curved tip for measuring sound-induced displacement of the auditory ossicles.

APPROACH

A handheld vibrometer probe guiding the laser beam with a fiber-optic cable was used for displacement measurements of the incus body and the posterior crus of the stapes. Tonal stimuli at frequencies of 0.5, 1, 2, and 4 kHz were presented by means of an insert earphone positioned in the outer ear canal. The probe was fixed at the measurement site using a tripod or hand-held by one of the two surgeons.

RESULTS

The measurements were carried out on six fresh temporal bones. Multivariate analysis of variance showed statistically significant differences for stimulus frequency (F3,143  =  29.37, p  <  0.001, and η2  =  0.35), bone (F5,143  =  4.61, p  =  0.001, and η2  =  0.01), and measurement site (F1,143  =  4.74, p  =  0.03, and η2  =  0.02) in the absence of statistically significant differences for the probe fixation method (F2,143  =  0.15, p  =  0.862, and η2  =  0.001). Standard deviations of the means were 6.9, 2.6, 1.9, and 0.6  nm  /  Pa for frequency, bone, site, and fixation, respectively. Ear transfer functions were found to be consistent with literature data.

CONCLUSIONS

The feasibility of applying HLFVP to measure the displacement of auditory ossicles has been confirmed. HLFVP offers the possibility of carrying out measurements at various angles; however, this needs to be standardized taking into account anatomical limitations and surgical convenience.

Does The Type of Ossicular Chain Lesion Affect Outcomes in Chronic Suppurative Otitis Media Without Cholesteatoma?

OBJECTIVES

We evaluated the pattern of ossicular chain (OC) lesion in chronic suppurative otitis media (CSOM) without cholesteatoma and its impact on outcomes in primary and revision surgeries.

MATERIALS AND METHODS

This was a retrospective chart review. Patients who underwent tympanoplasty due to CSOM with OC defect between 2010 and 2015 were included in the study.

RESULTS

OC lesions were found during 40 of 147 tympanoplasties performed due to CSOM. The preoperative air-bone gap (ABG) was greater in both discontinuity and fixation cases than in cases with CSOM with an intact OC (p<0.001). Twenty-nine patients were followed up postoperatively, after excluding four patients with stapes footplate fixation, in whom stapedotomy was not performed simultaneously. Among the 29 patients, the audiological results were similar in cases of discontinuity and fixation regarding gap change, residual ABG, and the rate of successful ossiculoplasty. Primary tympanoplasties provided better results according to postoperative ABG and the rate of successful ossiculoplasty than revision surgeries (p<0.05); however, similar patterns of OC lesions were found during primary and revision surgeries.

CONCLUSION

Both OC discontinuity and fixation occur in CSOM in a similar distribution in primary tympanoplasties and revision surgeries. The type of OC lesion does not affect outcomes. Primary surgeries provide better results, but that is not due to a difference in the character of the OC lesion.